Search

Sound field control can be applied to the problem of reducing noise emissions from outdoor live music events. One method employed in this type of applications is pressure matching. Different approaches can be used to find a solution to this problem. Many of these methods can provide reduction of more than 10 dB in the frequency range of a subwoofer, between 30 and 120 Hz, thus reducing the loudness to half the original. Such a performance is adequate, but it comes with drawbacks and/or practical limitations such as side lobes that can create new problems in new areas, computational cost, difficult parameter selection, etc. The method proposed here uses the conjugate gradient least square to compute a solution while providing an easier way to find a suitable regularization and at the same time controlling the radiation pattern of the solution to reduce the possibility of side lobes. In addition, the use of an active set-type methods allows to include explicit constraints on the amplitude of the solution to avoid amplification and non-linear behavior of the transducers. After introducing the theory, the performances are compared to other more established methods through simulations and outdoor measurements performed at a 2:1 scale to show properties and practical aspects of the method proposed. These experiments show that 10 dB insertion loss are achieved over a broad frequency range with peaks larger than 20 dB. We investigate the difference in performance between the different methods and use simulated versus measured transfer functions to derive the filters. We also analyze the numerical properties of the solutions provided by the different methods and relate them to the spatial properties of the corresponding sound fields. Furthermore, we present a convergence study to evaluate the effect that grids of different resolutions used in the simulations have on the insertion loss for different degrees of regularization. Finally, we present also a sensitivity analysis of

Active control of noise propagating through apertures is commonly realized with closed-loop LMS algorithms. However, these algorithms require a large number of error microphones and provide only local attenuation. Slow convergence and high computational effort are additional disadvantages. We propose a wave-domain approach that converges instantaneously, operates with low computational effort and does not require error microphones. It inherently controls sound in all directions in the far-field. The soundfield from the aperture is matched in a least squares sense with the generated soundfield from the loudspeaker array using orthonormal basis functions. Compensation for algorithmic delay, induced by blockwise processing, can be based on microphone placement or signal prediction, at the cost of a loss in attenuation performance. Our simulation results indicate that wave-domain processing has the potential to outperform LMS-based methods in practical active noise control for apertures., Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public., Signal Processing Systems, Team Riccardo Ferrari

STL describes the accumulated decrease in sound intensity as waves spread outward from a source or through specific areas. To reduce the sound transmission from the cylinder, an acoustic quieting process needs to be implemented. One of the most efficient ways to reduce sound transmission is using piezoelectric materials. Piezoelectric materials can be applied to reduce transmitted noise from different structures versus damping approaches when it is difficult to completely dampen structural vibrations via passive methods. The aim of the present study is to analyze the dynamic characteristics of piezo-laminated cylindrical structures for vibration suppression and control of sound transmission losses. Two thick shell models were developed to consider the effects of anisotropicity and piezoelectricity on the STL. In the first model, a 3D piezoelectric model is built to investigate the free vibration of a triclinic piezoelectric cylinder. In the second model, the estimation of STL due to the piezoelectric effects is studied for a piezo-composite cylinder excited by an incident plane wave. These two initial models enable us to explore deeper and study the effect of feedback control strategy for the enhancement of STL. The active control strategy is achieved by sending the control signal from the distributed piezoelectric sensor layer through a controller to drive the external actuators. The second model was also used to increase STL by using the different sizes and arrangements of piezoelectric electrodes. The study shows that increasing the number of electrodes may not necessarily provide higher soundproofing abilities. However, the level of sound isolation can be adjusted by using the proper size of the electrode. Finally, to go one more step deeper, considering the fluid-solid shear interaction, a new 3D elastic model incorporating the piezoelectricity and fluid viscosity is developed to simulate the dynamics and STL of a shell submerged in a viscous fluid. Parametric

Traditional active noise control (ANC) systems rely on a physical sensor to measure the error signal at the desired location of attenuation. The error signal is then used to update an adaptive controller, which ultimately attenuates the measured response. However, it is not always practical to use traditional ANC in real-world applications. For example, as small unmanned aerial systems (UAS) become more commonly used, community noise exposure also increases, along with the desire to reduce UAS noise. Traditional ANC systems that rely on physical sensors at observer locations are impractical, since a UAS does not typically have real-time access to the response at an observer's ears, which is realistically in the far-field. Virtual error sensing (VES) can augment an ANC system using near-field measurements to estimate the response at a desired far-field location. In this way, the VES technique effectively shifts the zone of quiet from the location of the physical sensor(s) to a different "virtual" location. This thesis begins by outlining past work that used traditional ANC methods and virtual error sensing techniques. Numerical modeling results showing the predicted spatial change in SPL achieved using a virtual sensor will be presented. Experimental tests used ANC to attenuate the noise from a single UAS rotor at far-field locations using a near-field microphone and the remote microphone technique (RMT) to develop the VES. The results of the VES alone and with an ANC approach at several far-field virtual locations will be presented and discussed.

Noise pollution is a major health threat to society. Active noise control systems that attenuate noise through open windows have the potential to create quieter homes while maintaining ventilation and sight. Such systems are commonly realized with closed-loop LMS algorithms. However, these algorithms require a large number of error microphones inside the room and provide only local attenuation. Using many error microphones leads to slow convergence and high computational effort, having additional disadvantages. Therefore, closed-loop active noise control algorithms are undesired for real-world application. In this study, we develop an open-loop wave-domain algorithm that converges instantaneously and operates with low computational effort. As it is open-loop, it does not require error microphones. We position a control region in the far-field that covers all directions from the aperture into the room. In the algorithm, we minimize the sound in that control region. Hence, it inherently ensures cancellation in the whole room. We derive acoustic transfer functions to obtain frequency responses of the aperture and loudspeakers. Those are used for soundfield calculation. The sum of the soundfields, from the aperture and the loudspeaker array, is then expressed in orthonormal basis functions. By minimizing this sum in least mean square sense, we can calculate the filter-weights that minimize the sound energy in the control region. Implementation of these filter-weights with block-wise processing using the Short-Time Fourier Transform generates the signals for the loudspeaker array. However, this processing induces a delay. To compensate for this algorithmic delay, two methods are compared. The first is positioning a reference microphone further in front of the aperture. The second method uses an autoregressive model for signal prediction. Both lead to a loss in attenuation performance compared to the optimal algorithm. We compare the optimal wave-domain algorithm with a L, Mechanical Engineering | Systems and Control

A wind tunnel from the 1950s located in Bromma, Stockholm, once used for military research is today used for commercial activities. Today the tunnel is used for indoor wingsuit flight and the facility has an interest in reducing the overall noise generated by the tunnel. Acoustic measurements indicate noise problems in the 50 Hz range. A 3D and a 2D model was structured with physical measured dimensions of the wind tunnel for simulations.Results indicate that a 37 dB decrease of the second higher order azimuthal spinning mode was achievable with the same number of monopole anti-sources as fan blades with each individual monopole modeling an enclosed loudspeakers. This acoustic mode was identified as the most problematic due to the cut-on frequency for the geometry coinciding with the fundamental blade pass frequency of the fan source during normal operating conditions., På 1950-talet byggdes en vindtunnel i Bromma, Stockholm kallad "LT1". Vindtunneln användes då för militär utveckling för bland annat flygförsvaret. Idag drivs den efter en period utan användning kommersiellt för flygning av ekorrdräkt så kallad "Wingsuit" inomhus. Området kring tunneln har kommersialierats under tiden den var ur drift och omgivande verksamheter påverkas av ljud från vindtunnelns verksamhet varför tunnelns verksamhet söker förbättringsmöjligheter avseende bullerdämpning. Akustiska mätningar i och utanför tunneln indikerar ett problemområde kring frekvensen 50 Hz som härstammar från den stora fläkt som skapar flödet i tunneln. Vindtunneln modellerades i 3D och 2D med hjälp av fysiskt uppmätta dimensioner på plats. Modellerna användes sedan för att kunna numeriskt simulera och beräkna möjligheten att dämpa ljudet från fläkten med hjälp av aktiv kontroll. Resultaten indikerar att en 37 dB ljudreduktion är möjlig av andra ordningens högre akustiska snurrande mod. Detta var möjligt att uppnå med lika många anti-källor modellerade som monopoler vilket motsvarar slutna högtalare, som fläktblad. Denna akustiska mod identifierades som den mest problematiska eftersom cut-on frekvensen för tunnelns geometri sammanfaller med den fundamentala bladpass-frekvensen för fläkten under normal drift.

A wind tunnel from the 1950s located in Bromma, Stockholm, once used for military research is today used for commercial activities. Today the tunnel is used for indoor wingsuit flight and the facility has an interest in reducing the overall noise generated by the tunnel. Acoustic measurements indicate noise problems in the 50 Hz range. A 3D and a 2D model was structured with physical measured dimensions of the wind tunnel for simulations.Results indicate that a 37 dB decrease of the second higher order azimuthal spinning mode was achievable with the same number of monopole anti-sources as fan blades with each individual monopole modeling an enclosed loudspeakers. This acoustic mode was identified as the most problematic due to the cut-on frequency for the geometry coinciding with the fundamental blade pass frequency of the fan source during normal operating conditions., På 1950-talet byggdes en vindtunnel i Bromma, Stockholm kallad "LT1". Vindtunneln användes då för militär utveckling för bland annat flygförsvaret. Idag drivs den efter en period utan användning kommersiellt för flygning av ekorrdräkt så kallad "Wingsuit" inomhus. Området kring tunneln har kommersialierats under tiden den var ur drift och omgivande verksamheter påverkas av ljud från vindtunnelns verksamhet varför tunnelns verksamhet söker förbättringsmöjligheter avseende bullerdämpning. Akustiska mätningar i och utanför tunneln indikerar ett problemområde kring frekvensen 50 Hz som härstammar från den stora fläkt som skapar flödet i tunneln. Vindtunneln modellerades i 3D och 2D med hjälp av fysiskt uppmätta dimensioner på plats. Modellerna användes sedan för att kunna numeriskt simulera och beräkna möjligheten att dämpa ljudet från fläkten med hjälp av aktiv kontroll. Resultaten indikerar att en 37 dB ljudreduktion är möjlig av andra ordningens högre akustiska snurrande mod. Detta var möjligt att uppnå med lika många anti-källor modellerade som monopoler vilket motsvarar slutna högtalare, som fläktblad. Denna akustiska mod identifierades som den mest problematiska eftersom cut-on frekvensen för tunnelns geometri sammanfaller med den fundamentala bladpass-frekvensen för fläkten under normal drift.

In this work we explore online secondary path modelling (SPM) in the context of spatial active noise control (ANC). Specifically, we are interested in the reduction of broadband noise over a three-dimensional region, without restrictions on microphone and loudspeaker array placement. As spatial ANC generally requires many channels, both ANC and SPM methods must have low computational cost. The SPM methods are intended to be used with a specific spatial ANC algorithm based on kernel interpolation. By incorporating SPM, the spatial ANC method is enabled to operate under timevarying secondary paths. Four SPM methods are considered in detail, of which three are based on the auxiliary noise technique. Descriptions of the algorithms are presented for the multichannel case, in addition to block-based implementations taking advantage of the fast Fourier transform to drastically reduce computational cost. Impulse responses to simulate a soundfield are recorded using a programmable robot arm. The algorithms are evaluated through simulations to show their respective strengths and weaknesses. It is found that the auxiliary noise based SPM methods have good convergence properties for both control filter and secondary path estimate, although the auxiliary noise’s degrading effect on the residual noise leads to a similar total noise reduction as the auxiliary noise free method. For all algorithms, the noise control performance worsens, and the convergence time increases by more than an order of magnitude, compared to when the secondary paths are known. It is verified that the kernel interpolation based spatial ANC method successfully reduces noise over a region even when used with online SPM., I detta projekt undersöks sekundärvägsmodellering för spatial aktiv brusreducering. Fokus ligger på minskning av brus över en tredimensionell region, för metoder utan några restriktioner när det gäller mikrofon- och högtalarplacering. Efterssom spatial brusreducering generellt kräver många kanaler, behöver både sekundärvägsmodellering samt brusreducering ha mycket låg beräkningskostnad. Metoderna för sekundärvägsmodellering är menade att användas tillsammans med en specifik spatial brusreduceringsalgoritm baserad på kärninterpolation. Genom att inkludera sekundärvägsmodellering kan den spatiala brusreduceringsmetoden operera även då sekundärvägarna är tidsvarierande. Fyra metoder för sekundärvägsmodellering är undersökta i detalj, tre av vilka är baserade på auxiliärbrusprincipen. Dessa algoritmer är beskrivna för multikanalsfallet, tillsammans med blockbaserade implementationer som utnyttjar den snabba Fouriertransformen för att drastiskt minska sina beräkningskostader. Impulssvar som kan användas för att simulera ett ljudfält är inspelade med hjälp av en programmerbar robotarm. Algoritmerna är utvärderade genom simuleringar för att visa deras respektive styrkor och svagheter. Experimenten visade att de algoritmer som använder sig av auxiliärbrus har bra konvergenskaraktäristik för både kontrollfilter och sekundärvägsestimat. Däremot, på grund av auxiliärbrusets negativa inverkan på residualbruset i rummet, är den totala brusreduceringen snarlik det den auxiliärbrusfria metoden ger. För alla algoritmer blir brusreduceringen försämrad och konvergenstiden ökad med mer än en storleksordning när sekundärvägsmodellering används, jämfört med när sekundärvägarna är kända. Det verifierades också att den spatiala brusreduceringsmetoden baserad på kärninterpolation kan reducera brus över en region även när den används tillsammans med sekundärvägsmodellering.

In this work we explore online secondary path modelling (SPM) in the context of spatial active noise control (ANC). Specifically, we are interested in the reduction of broadband noise over a three-dimensional region, without restrictions on microphone and loudspeaker array placement. As spatial ANC generally requires many channels, both ANC and SPM methods must have low computational cost. The SPM methods are intended to be used with a specific spatial ANC algorithm based on kernel interpolation. By incorporating SPM, the spatial ANC method is enabled to operate under timevarying secondary paths. Four SPM methods are considered in detail, of which three are based on the auxiliary noise technique. Descriptions of the algorithms are presented for the multichannel case, in addition to block-based implementations taking advantage of the fast Fourier transform to drastically reduce computational cost. Impulse responses to simulate a soundfield are recorded using a programmable robot arm. The algorithms are evaluated through simulations to show their respective strengths and weaknesses. It is found that the auxiliary noise based SPM methods have good convergence properties for both control filter and secondary path estimate, although the auxiliary noise’s degrading effect on the residual noise leads to a similar total noise reduction as the auxiliary noise free method. For all algorithms, the noise control performance worsens, and the convergence time increases by more than an order of magnitude, compared to when the secondary paths are known. It is verified that the kernel interpolation based spatial ANC method successfully reduces noise over a region even when used with online SPM., I detta projekt undersöks sekundärvägsmodellering för spatial aktiv brusreducering. Fokus ligger på minskning av brus över en tredimensionell region, för metoder utan några restriktioner när det gäller mikrofon- och högtalarplacering. Efterssom spatial brusreducering generellt kräver många kanaler, behöver både sekundärvägsmodellering samt brusreducering ha mycket låg beräkningskostnad. Metoderna för sekundärvägsmodellering är menade att användas tillsammans med en specifik spatial brusreduceringsalgoritm baserad på kärninterpolation. Genom att inkludera sekundärvägsmodellering kan den spatiala brusreduceringsmetoden operera även då sekundärvägarna är tidsvarierande. Fyra metoder för sekundärvägsmodellering är undersökta i detalj, tre av vilka är baserade på auxiliärbrusprincipen. Dessa algoritmer är beskrivna för multikanalsfallet, tillsammans med blockbaserade implementationer som utnyttjar den snabba Fouriertransformen för att drastiskt minska sina beräkningskostader. Impulssvar som kan användas för att simulera ett ljudfält är inspelade med hjälp av en programmerbar robotarm. Algoritmerna är utvärderade genom simuleringar för att visa deras respektive styrkor och svagheter. Experimenten visade att de algoritmer som använder sig av auxiliärbrus har bra konvergenskaraktäristik för både kontrollfilter och sekundärvägsestimat. Däremot, på grund av auxiliärbrusets negativa inverkan på residualbruset i rummet, är den totala brusreduceringen snarlik det den auxiliärbrusfria metoden ger. För alla algoritmer blir brusreduceringen försämrad och konvergenstiden ökad med mer än en storleksordning när sekundärvägsmodellering används, jämfört med när sekundärvägarna är kända. Det verifierades också att den spatiala brusreduceringsmetoden baserad på kärninterpolation kan reducera brus över en region även när den används tillsammans med sekundärvägsmodellering.

Noise pollution is a major health threat to society. Active noise control systems that attenuate noise through open windows have the potential to create quieter homes while maintaining ventilation and sight. Such systems are commonly realized with closed-loop LMS algorithms. However, these algorithms require a large number of error microphones inside the room and provide only local attenuation. Using many error microphones leads to slow convergence and high computational effort, having additional disadvantages. Therefore, closed-loop active noise control algorithms are undesired for real-world application. In this study, we develop an open-loop wave-domain algorithm that converges instantaneously and operates with low computational effort. As it is open-loop, it does not require error microphones. We position a control region in the far-field that covers all directions from the aperture into the room. In the algorithm, we minimize the sound in that control region. Hence, it inherently ensures cancellation in the whole room. We derive acoustic transfer functions to obtain frequency responses of the aperture and loudspeakers. Those are used for soundfield calculation. The sum of the soundfields, from the aperture and the loudspeaker array, is then expressed in orthonormal basis functions. By minimizing this sum in least mean square sense, we can calculate the filter-weights that minimize the sound energy in the control region. Implementation of these filter-weights with block-wise processing using the Short-Time Fourier Transform generates the signals for the loudspeaker array. However, this processing induces a delay. To compensate for this algorithmic delay, two methods are compared. The first is positioning a reference microphone further in front of the aperture. The second method uses an autoregressive model for signal prediction. Both lead to a loss in attenuation performance compared to the optimal algorithm. We compare the optimal wave-domain algorithm with a L, Mechanical Engineering | Systems and Control

Metamaterials are periodic structures which offer physical properties not found in nature. Particularly, acoustic metamaterials can manipulate sound and elastic waves both spatially and spectrally in unpreceded ways. Acoustic metamaterials can generate arbitrary acoustic bandgaps by scattering sound waves, which is a superior property for insulation properties. In this study, one dimension of the resonators (depth of cavity) was altered by means of a pneumatic actuation system. To this end, metamaterial slabs were additively manufactured and connected to a proportional pressure control unit. The noise reduction performance of active acoustic metamaterials in closed-and open-space configurations was measured in different control conditions. The pneumatic actuation system was used to vary the pressure behind pistons inside each cell of the metamaterial, and as a result to vary the cavity depth of each unit cell. Two pressures were considered, P = 0.05 bar, which led to higher depth of the cavities, and P = 0.15 bar, which resulted in lower depth of cavities. The results showed that by changing the pressure from P = 0.05 (high cavity depth) to P = 0.15 (low cavity depth), the acoustic bandgap can be shifted from a frequency band of 150-350 Hz to a frequency band of 300-600 Hz. The pneumatically-actuated acoustical metamaterial gave a peak attenuation of 20 dB (at 500 Hz) in the closed system and 15 dB (at 500 Hz) in the open system. A step forward would be to tune different unit cells of the metamaterial with different pressure levels (and therefore different cavity depths) in order to target a broader range of frequencies., Novel Aerospace Materials

Barriers are increasingly used to protect the pedestrian and neighboring buildings from construction noise activities. This study aims to investigate the suitability of applying active noise control on barriers in a construction site to protect the street area and neighboring buildings. Transducers that are simulated in this work are close to the barrier, and their optimal positions are defined in such a way that the control system has the maximum performance at the neighboring areas close to the construction sites. To begin with, the suitable location of the control sources is found when the total squared pressure is minimized at the positions of noise receivers. The suitable location of the error sensors is, then, found when the control sources are fixed at the position of the previous step and the total squared pressure isminimized at the error sensors. The best location for the error sensors is defined when the maximum reduction is achieved in the target area. It is observed that suitable positions for the transducers depend on the location of target areas for noise control, the position of the noise source, and its operating frequency. In this investigation, a unique configuration is proposed for the transducers that achieves a comparable reduction both at the street area and the neighboring buildings, simultaneously. The results show that the active noise barrier with a height of 2.5 m can achieve an extra insertion loss in the street zone, varies from 9.3 to 16.4 dB (in comparison with passive noise barrier) when the distance of the noise source from the barrier changes in the range of 7 to 1 m, respectively. Those values are of the same order for the passive noise attenuation. Furthermore, similar results are achieved when attempting to cancel the shadow zone of a façade 15 m away from the barrier., Peer Reviewed, Postprint (published version)

Metamaterials are periodic structures which offer physical properties not found in nature. Particularly, acoustic metamaterials can manipulate sound and elastic waves both spatially and spectrally in unpreceded ways. Acoustic metamaterials can generate arbitrary acoustic bandgaps by scattering sound waves, which is a superior property for insulation properties. In this study, one dimension of the resonators (depth of cavity) was altered by means of a pneumatic actuation system. To this end, metamaterial slabs were additively manufactured and connected to a proportional pressure control unit. The noise reduction performance of active acoustic metamaterials in closed-and open-space configurations was measured in different control conditions. The pneumatic actuation system was used to vary the pressure behind pistons inside each cell of the metamaterial, and as a result to vary the cavity depth of each unit cell. Two pressures were considered, P = 0.05 bar, which led to higher depth of the cavities, and P = 0.15 bar, which resulted in lower depth of cavities. The results showed that by changing the pressure from P = 0.05 (high cavity depth) to P = 0.15 (low cavity depth), the acoustic bandgap can be shifted from a frequency band of 150-350 Hz to a frequency band of 300-600 Hz. The pneumatically-actuated acoustical metamaterial gave a peak attenuation of 20 dB (at 500 Hz) in the closed system and 15 dB (at 500 Hz) in the open system. A step forward would be to tune different unit cells of the metamaterial with different pressure levels (and therefore different cavity depths) in order to target a broader range of frequencies., Novel Aerospace Materials

Щороку в місті, поблизу житлових районів, проводяться все більше і більше open air заходів та великих концертів. Головною проблемою цього є шумове забруднення прилежних районів. З іншого боку, невід'ємною частиною таких концертів є високий рівень звукового тиску. Створення звукових зон є одним з можливих шляхів вирішення цієї проблеми. У даній роботі ми розглянемо та охарактеризуємо основні способи створення звукових зон: акустичний контраст, pressure matching та комбінований метод. Розглянуто також класичний метод активного контролю шуму на основі алгоритму найменших квадратів. Для всіх методів отримані кінцеві вирази для розрахунку оптимальних комплексних об'ємних швидкостей гучномовців. Описано значення параметрів регуляції цих методів. Для обчислення звукових зон використовуються виміряні або змодельовані передатні характеристики розповсюдження звуку. У цій роботі вивчається вплив навколишнього середовища та атмосферних умов. Моделювання всіх методів проводилося у середовищі MATLAB. Порівняння результатів проводилося за розрахунковими показниками продуктивності та за частотною характеристикою розрахованих оптимальних ваг. Важливість параметрів регулювання показана при моделюванні різних методів. Для досліджуваної системи обраний оптимальний метод. В цілому метою цієї роботи є порівняння та пошук оптимального методу створення звукових зон, який використовується для управління великими зонами в межах open air події; а також зробити оцінку можливого впливу атмосферних умов на точність і надійність цих методів., Every year more and more open-air events and large concerts are held in the city, near residential areas. The main problem of this is noise pollution in nearby areas. On the other hand, an integral part of such concerts is a high SPL. Creating sound zones is one possible solution to this problem. In this paper, we examine and characterize the main methods of creating sound zones: Acoustic Contrast, Pressure Matching and combined method. The classical method of active noise control based on the LMS algorithm is also considered. For all methods, final expressions are derived for calculating the optimal complex volume velocities of the loudspeakers. The meaning of regularization parameters of these methods is described. To calculate the sound zones, measured or modeled propagation transfer functions are used. The effect of the environment and atmospheric conditions is studied in this work and their impact is evaluated. Simulations of all methods were performed at MATLAB. Comparison of the results was carried out on the calculated performance metrics and on the frequency response of the calculated optimal weights. The importance of the regulation parameters has been shown when simulating various methods. The optimal method was chosen for the system under study. In general, this work aimed to make a comparison and search for the optimal method for creating sound zones, which is used to control large zones within an open air event; and also make an assessment of the possible influence of atmospheric conditions on the accuracy and robustness of these methods., Ежегодно в городе, вблизи жилых районов, проводятся все больше и больше open air мероприятий и больших концертов. Главной проблемой этого является шумовое загрязнение прилегающей районов. С другой стороны, неотъемлемой частью таких концертов является высокий уровень звукового давления. Создание звуковых зон является одним из возможных путей решения этой проблемы. В данной работе мы рассмотрим и охарактеризуем основные способы создание звуковых зон: акустический контраст, pressure matching и комбинированный метод. Рассмотрены также классический метод активного контроля шума на основе алгоритма наименьших квадратов. Для всех методов полученные конечные выражения для расчета оптимальных комплексных объемных скоростей громкоговорителей. Описаны значения параметров регуляции этих методов. Для вычисления звуковых зон используются измеренные или смоделированы передаточные характеристики распространения звука. В этой работе изучается влияние окружающей среды и атмосферных условий. Моделирование всех методов проводилось в среде MATLAB. Сравнение результатов проводилось по расчетным показателям производительности и по частотной характеристикой рассчитанных оптимальных весов. Важность параметров регулирования показана при моделировании различных методов. Для исследуемой системы выбран оптимальный метод. В целом целью этой работы является сравнение и поиск оптимального метода создания звуковых зон, который используется для управления большими зонами в пределах open air события; а также сделать оценку возможного воздействию атмосферных условий на точность и надежность этих методов.

This dissertation is concerned with the active control of local sound fields, as applied to an active headrest system. Using loudspeakers and microphones, an active headrest is capable of attenuating ambient noise and providing a comfortable acoustic environment for an occupant. A finite element (FE) model of an active headrest is built and analyzed such that the expected noise reduction levels could be quantified for various geometries as well as primary sound field conditions. Both plane wave and diffuse primary sound fields are considered and it is shown that the performance deteriorates for diffuse sound fields. It is then demonstrated that virtual sensing can greatly improve the spatial extent of the quiet zones as well as the attenuation levels. A prototype of the active headrest was constructed, with characteristics similar to those of the FE model, and tested in both anechoic and reverberant sound fields. Multichannel feedforward and feedback control architectures are implemented in real-time and it is shown that adaptive feedback systems are capable of attenuating band-limited disturbances. The spatial attenuation pattern surrounding the head is also measured by shifting the head to various positions and measuring the attenuation at the ears. Two virtual sensing techniques are compared in both feedback and feedforward architectures. The virtual microphone arrangement, which assumes that the primary sound field is equivalent at the physical and virtual locations, results in the best performance when used in a feedback system attenuating broadband disturbances. The remote microphone technique, which accounts for the transfer response between the physical and virtual locations, offers the best performance for tonal primary sound fields. In broadband sound fields, a causal relationship rarely exists between the physical and virtual microphones, resulting in poor performance.

Noise pollution from road traffic is one of the greatest environmental issues in modern day, and the social cost for road traffic noise was estimated to over 16 billion SEK per year in Sweden in2014. Passive or active control methods can be used to reduce the noise. Active control methods or active noise control is more suitable for attenuating noise in lower frequencies. Active noise control reduces noise by eliminating the noise with a secondary source. There are different control strategies to construct an active noise control system, where the update of the secondary sourceis controlled by an algorithm. There are several different algorithms that are possible to use, and one option is to use a Feedforward Filtered-X Least-Mean-Square (FXLMS) algorithm. It uses control positions where the noise is meant to be reduced and reference signals that measure the noise upstream prior the secondary source. FXLMS also uses a model of the secondary source path to the control position in order to ensure convergence of the algorithm. Although the use of multiple reference signals increases the accuracy of the algorithm, it also increases the convergence time and the practical cost of such an installation. Unfortunately, it can require many reference signals to obtain a sufficient noise reduction when the unwanted noise source is complex and has multiple propagation paths.This study investigates the possibility of producing a new, reduced set of reference signals with a linear combination of the original reference signals that still contain the majority of information needed for suficient noise reduction. This new set of reference signals are sometimes called virtual reference signals. Three different methods of virtual reference signals are analysed; first a constant method using singular-value decomposition on the covariance of the reference signals, second another constant method using singular-value decomposition on the covariance of response estimate from each correspondi

This dissertation is concerned with the active control of local sound fields, as applied to an active headrest system. Using loudspeakers and microphones, an active headrest is capable of attenuating ambient noise and providing a comfortable acoustic environment for an occupant. A finite element (FE) model of an active headrest is built and analyzed such that the expected noise reduction levels could be quantified for various geometries as well as primary sound field conditions. Both plane wave and diffuse primary sound fields are considered and it is shown that the performance deteriorates for diffuse sound fields. It is then demonstrated that virtual sensing can greatly improve the spatial extent of the quiet zones as well as the attenuation levels. A prototype of the active headrest was constructed, with characteristics similar to those of the FE model, and tested in both anechoic and reverberant sound fields. Multichannel feedforward and feedback control architectures are implemented in real-time and it is shown that adaptive feedback systems are capable of attenuating band-limited disturbances. The spatial attenuation pattern surrounding the head is also measured by shifting the head to various positions and measuring the attenuation at the ears. Two virtual sensing techniques are compared in both feedback and feedforward architectures. The virtual microphone arrangement, which assumes that the primary sound field is equivalent at the physical and virtual locations, results in the best performance when used in a feedback system attenuating broadband disturbances. The remote microphone technique, which accounts for the transfer response between the physical and virtual locations, offers the best performance for tonal primary sound fields. In broadband sound fields, a causal relationship rarely exists between the physical and virtual microphones, resulting in poor performance.

Noise pollution from road traffic is one of the greatest environmental issues in modern day, and the social cost for road traffic noise was estimated to over 16 billion SEK per year in Sweden in2014. Passive or active control methods can be used to reduce the noise. Active control methods or active noise control is more suitable for attenuating noise in lower frequencies. Active noise control reduces noise by eliminating the noise with a secondary source. There are different control strategies to construct an active noise control system, where the update of the secondary sourceis controlled by an algorithm. There are several different algorithms that are possible to use, and one option is to use a Feedforward Filtered-X Least-Mean-Square (FXLMS) algorithm. It uses control positions where the noise is meant to be reduced and reference signals that measure the noise upstream prior the secondary source. FXLMS also uses a model of the secondary source path to the control position in order to ensure convergence of the algorithm. Although the use of multiple reference signals increases the accuracy of the algorithm, it also increases the convergence time and the practical cost of such an installation. Unfortunately, it can require many reference signals to obtain a sufficient noise reduction when the unwanted noise source is complex and has multiple propagation paths.This study investigates the possibility of producing a new, reduced set of reference signals with a linear combination of the original reference signals that still contain the majority of information needed for suficient noise reduction. This new set of reference signals are sometimes called virtual reference signals. Three different methods of virtual reference signals are analysed; first a constant method using singular-value decomposition on the covariance of the reference signals, second another constant method using singular-value decomposition on the covariance of response estimate from each correspondi

This paper deals with nonlinear active noise control using adaptive wavelet filters. The ability of wavelets in signal reconstruction and function approximation make them appealing for black box system identification. Moreover, the intrinsic similarity between wavelet filters and noise/vibration signals implies that better approximation of these signals can be achieved by employing wavelet filters. Here, a new simple structure for using in active noise control system is proposed comprises a nonlinear static mapping cascaded with an IIR filter to take care of the dynamics of the system. With this strategy, one can avoid using multi-dimensional wavelet networks and thus eliminate curse of dimensionality. The performance of the proposed ANC system is examined for typical linear/nonlinear cases. The simulation results demonstrate superior performance of this method in terms of fast convergence rate and noise attenuation as well as computational complexity reduction while avoiding curse of dimensionality.

High quality noise and vibration measurements outside of a laboratory environment on real life structures and applications are not trivial. True boundary and operating conditions enforce unique challenges on the measurements. Measurements in hazardous situations such as high magnetic fields, and high temperature environments, etc., where ordinary measurement equipment and methods may not be employed, require further precautions. Post measurements objectives such as analysis, design and strategic decisions, e.g., control, rely heavily on the quality and integrity of the measurements (data). The quality of the experimental data is highly correlated with the on-field expertise. Practical or hands-on experience with measurements can be imparted to prospective students, researchers and technicians in the form of laboratory experiments involving real equipment and practical applications. However, achieving expertise in the field of sound and vibration measurements in general and their active control in particular is a time consuming and expensive process. Consequently most institutions can only afford a single setup, resulting in the compromise of the quality of expertise. In this thesis, the challenges in the field of sound and vibration measurements in high magnetic field are addressed. The analysis and measurement of vibration transferred from an operational magnetic resonance imaging (MRI) scanner to adjacent floors is taken as an example. Improvised experimental measurement methods and custom-made frequency analysis techniques are proposed in order to address the challenges and study the vibration transfer. The methods may be extended to other operational industrial machinery and hazardous environments. To encourage and develop expertise in the field of acoustic/vibration measurements and active noise control on practical test beds, remotely controlled laboratory setups are introduced. The developed laboratory setup, which is accessed and controlled via the Internet

The aim of the thesis is to upgrade an existing Remote Laboratory for Active Noise Control (ANC) and acoustics experiments providing users with a more authentic real life experience. This is done by designing a solution that allows remote position control of microphones inside a ventilation duct for ANC experiments. The suggested features to be implemented substantially improve the flexibility of the existing remote laboratory, based on the Virtual Instrument System in Reality (VISIR) platform, as well as providing more control over the system as a whole. The work in the project may be divided into the following steps: theoretical design of mechanical and electrical parts of the system along with control algorithms which include a study of similar solutions and related work, implementation of designed system, subsequent testing of the system, connecting the implemented system to the equipment for remote communication and adding the appropriate features to the remote control interface.

Komatsu Forrest AB have a demand for a media solution where the user can select between different input sources as well as output channels. The input sources are Radio, Bluetooth, AUX, two microphones and PC. The system shall also be able to mix sound from an ANC unit (Active Noise Control). Due to the demands from the company, the system must be able to be digitally controlled. The goal is to present a concept that offers the solution for these demands.To specify the needs from the user a dialog with employees with more knowledge about the user’s use have resulted in a table. From this a technical design has been created and resulted in a technical design requirement. With the design structure as a base, simulations have been done. After the structure has been verified by simulations a prototype with the basic functions have been designed and programmed and verified to clarify the function.Simulations and measurements have shown that the design works as desired. The result shows that the unit can meet the requirements set by the company in a user-friendly manner. The project has resulted in different solutions and these evaluated for pros and cons compared to the chosen solution., Komatsu Forest AB behöver en multimedialösning för att uppfylla specifika behov exempelvis simultant användande av två mobiltelefoner och två mikrofoner. Enheten ska klara av att hantera ljud från flertalet ljudkällor samt två mikrofoner och aktiv bullerreducering. Systemet ska styras digitalt från till exempel en PC. Målet är att presentera ett koncept som erbjuder en lösning för dessa problem.Utformningen av enheten har gjorts genom att utvärdera användarens bruksområden tillsammans med den vision som legat till grund för projektet. Detta har genom samtal med anställda på företaget medfört en sammanställning över förarens användnings-områden. Utifrån denna sammanställning av användningsområdena har en teknisk skiss för enhetens uppbyggnad möjliggjorts. Efter att funktionen för skissen har verifierats med simuleringar har ett prototypkort för enhetens grundstomme konstrueras, programmerats samt verifierat konstruktionen.Simuleringar och mätningar verifierar att konstruktionen fungerar som önskat. Resultatet visar att enheten skulle uppfylla de uppsatta önskemålen på ett bra och användarvänligt sätt. Då flera lösningar har tagits fram under projektets gång diskuteras för och nackdelar med dessa samt motiveras varför den valda lösningen är bäst anpassad.

[EN] In this paper, we present a distributed affine projection (AP) algorithm for an acoustic sensor network where the nodes are acoustically coupled. Every acoustic node is composed of a microphone, a processor, and an actuator to control the sound field. This type of networks can use distributed adaptive algorithms to deal with the active noise control (ANC) problem in a cooperative manner, providing more flexible and scalable ANC systems. In this regard, we introduce here a distributed version of the multichannel filtered-x AP algorithm over an acoustic sensor network that it is called distributed filtered-x AP (DFxAP) algorithm. The analysis of the mean and the mean-square deviation performance of the algorithm at each node is given for a network with a ring topology and without constraints in the communication layer. The theoretical results are validated through several simulations. Moreover, simulations show that the proposed DFxAP outperforms the previously reported distributed multiple error filtered-x least mean square algorithm.

This paper deals with nonlinear active noise control using adaptive wavelet filters. The ability of wavelets in signal reconstruction and function approximation make them appealing for black box system identification. Moreover, the intrinsic similarity between wavelet filters and noise/vibration signals implies that better approximation of these signals can be achieved by employing wavelet filters. Here, a new simple structure for using in active noise control system is proposed comprises a nonlinear static mapping cascaded with an IIR filter to take care of the dynamics of the system. With this strategy, one can avoid using multi-dimensional wavelet networks and thus eliminate curse of dimensionality. The performance of the proposed ANC system is examined for typical linear/nonlinear cases. The simulation results demonstrate superior performance of this method in terms of fast convergence rate and noise attenuation as well as computational complexity reduction while avoiding curse of dimensionality.

This paper deals with nonlinear active noise control using adaptive wavelet filters. The ability of wavelets in signal reconstruction and function approximation make them appealing for black box system identification. Moreover, the intrinsic similarity between wavelet filters and noise/vibration signals implies that better approximation of these signals can be achieved by employing wavelet filters. Here, a new simple structure for using in active noise control system is proposed comprises a nonlinear static mapping cascaded with an IIR filter to take care of the dynamics of the system. With this strategy, one can avoid using multi-dimensional wavelet networks and thus eliminate curse of dimensionality. The performance of the proposed ANC system is examined for typical linear/nonlinear cases. The simulation results demonstrate superior performance of this method in terms of fast convergence rate and noise attenuation as well as computational complexity reduction while avoiding curse of dimensionality.

This paper deals with nonlinear active noise control using adaptive wavelet filters. The ability of wavelets in signal reconstruction and function approximation make them appealing for black box system identification. Moreover, the intrinsic similarity between wavelet filters and noise/vibration signals implies that better approximation of these signals can be achieved by employing wavelet filters. Here, a new simple structure for using in active noise control system is proposed comprises a nonlinear static mapping cascaded with an IIR filter to take care of the dynamics of the system. With this strategy, one can avoid using multi-dimensional wavelet networks and thus eliminate curse of dimensionality. The performance of the proposed ANC system is examined for typical linear/nonlinear cases. The simulation results demonstrate superior performance of this method in terms of fast convergence rate and noise attenuation as well as computational complexity reduction while avoiding curse of dimensionality.

El artículo aborda un problema contemporáneo que afecta a miles de ciudades del mundo: el ruido, específicamente, el ruido que generan las competencias de deportes a motor en los autódromos. Se esboza la situación de algunas pistas de diversos países que se han visto limitadas e, incluso, clausuradas por no cumplir con las normas de ruido exigidas por las autoridades ambientales. Tomando como marco teórico el control del ruido, se indaga en dos vertientes bien diferenciadas: el control pasivo del ruido y el control activo del ruido. Además y considerando que la normativa concerniente al ruido dista de ser homogénea a nivel internacional, se realiza una pesquisa inicial en ese sentido y se presentan sus resultados; con base en ellos, se busca elevar una solicitud formal a la autoridad ambiental colombiana para que modifique el umbral de ruido permitido en torno a los autódromos.

High quality noise and vibration measurements outside of a laboratory environment on real life structures and applications are not trivial. True boundary and operating conditions enforce unique challenges on the measurements. Measurements in hazardous situations such as high magnetic fields, and high temperature environments, etc., where ordinary measurement equipment and methods may not be employed, require further precautions. Post measurements objectives such as analysis, design and strategic decisions, e.g., control, rely heavily on the quality and integrity of the measurements (data). The quality of the experimental data is highly correlated with the on-field expertise. Practical or hands-on experience with measurements can be imparted to prospective students, researchers and technicians in the form of laboratory experiments involving real equipment and practical applications. However, achieving expertise in the field of sound and vibration measurements in general and their active control in particular is a time consuming and expensive process. Consequently most institutions can only afford a single setup, resulting in the compromise of the quality of expertise. In this thesis, the challenges in the field of sound and vibration measurements in high magnetic field are addressed. The analysis and measurement of vibration transferred from an operational magnetic resonance imaging (MRI) scanner to adjacent floors is taken as an example. Improvised experimental measurement methods and custom-made frequency analysis techniques are proposed in order to address the challenges and study the vibration transfer. The methods may be extended to other operational industrial machinery and hazardous environments. To encourage and develop expertise in the field of acoustic/vibration measurements and active noise control on practical test beds, remotely controlled laboratory setups are introduced. The developed laboratory setup, which is accessed and controlled via the Internet

The aim of the thesis is to upgrade an existing Remote Laboratory for Active Noise Control (ANC) and acoustics experiments providing users with a more authentic real life experience. This is done by designing a solution that allows remote position control of microphones inside a ventilation duct for ANC experiments. The suggested features to be implemented substantially improve the flexibility of the existing remote laboratory, based on the Virtual Instrument System in Reality (VISIR) platform, as well as providing more control over the system as a whole. The work in the project may be divided into the following steps: theoretical design of mechanical and electrical parts of the system along with control algorithms which include a study of similar solutions and related work, implementation of designed system, subsequent testing of the system, connecting the implemented system to the equipment for remote communication and adding the appropriate features to the remote control interface.

Komatsu Forrest AB have a demand for a media solution where the user can select between different input sources as well as output channels. The input sources are Radio, Bluetooth, AUX, two microphones and PC. The system shall also be able to mix sound from an ANC unit (Active Noise Control). Due to the demands from the company, the system must be able to be digitally controlled. The goal is to present a concept that offers the solution for these demands.To specify the needs from the user a dialog with employees with more knowledge about the user’s use have resulted in a table. From this a technical design has been created and resulted in a technical design requirement. With the design structure as a base, simulations have been done. After the structure has been verified by simulations a prototype with the basic functions have been designed and programmed and verified to clarify the function.Simulations and measurements have shown that the design works as desired. The result shows that the unit can meet the requirements set by the company in a user-friendly manner. The project has resulted in different solutions and these evaluated for pros and cons compared to the chosen solution., Komatsu Forest AB behöver en multimedialösning för att uppfylla specifika behov exempelvis simultant användande av två mobiltelefoner och två mikrofoner. Enheten ska klara av att hantera ljud från flertalet ljudkällor samt två mikrofoner och aktiv bullerreducering. Systemet ska styras digitalt från till exempel en PC. Målet är att presentera ett koncept som erbjuder en lösning för dessa problem.Utformningen av enheten har gjorts genom att utvärdera användarens bruksområden tillsammans med den vision som legat till grund för projektet. Detta har genom samtal med anställda på företaget medfört en sammanställning över förarens användnings-områden. Utifrån denna sammanställning av användningsområdena har en teknisk skiss för enhetens uppbyggnad möjliggjorts. Efter att funktionen för skissen har verifierats med simuleringar har ett prototypkort för enhetens grundstomme konstrueras, programmerats samt verifierat konstruktionen.Simuleringar och mätningar verifierar att konstruktionen fungerar som önskat. Resultatet visar att enheten skulle uppfylla de uppsatta önskemålen på ett bra och användarvänligt sätt. Då flera lösningar har tagits fram under projektets gång diskuteras för och nackdelar med dessa samt motiveras varför den valda lösningen är bäst anpassad.

El artículo aborda un problema contemporáneo que afecta a miles de ciudades del mundo: el ruido, específicamente, el ruido que generan las competencias de deportes a motor en los autódromos. Se esboza la situación de algunas pistas de diversos países que se han visto limitadas e, incluso, clausuradas por no cumplir con las normas de ruido exigidas por las autoridades ambientales. Tomando como marco teórico el control del ruido, se indaga en dos vertientes bien diferenciadas: el control pasivo del ruido y el control activo del ruido. Además y considerando que la normativa concerniente al ruido dista de ser homogénea a nivel internacional, se realiza una pesquisa inicial en ese sentido y se presentan sus resultados; con base en ellos, se busca elevar una solicitud formal a la autoridad ambiental colombiana para que modifique el umbral de ruido permitido en torno a los autódromos.

El artículo aborda un problema contemporáneo que afecta a miles de ciudades del mundo: el ruido, específicamente, el ruido que generan las competencias de deportes a motor en los autódromos. Se esboza la situación de algunas pistas de diversos países que se han visto limitadas e, incluso, clausuradas por no cumplir con las normas de ruido exigidas por las autoridades ambientales. Tomando como marco teórico el control del ruido, se indaga en dos vertientes bien diferenciadas: el control pasivo del ruido y el control activo del ruido. Además y considerando que la normativa concerniente al ruido dista de ser homogénea a nivel internacional, se realiza una pesquisa inicial en ese sentido y se presentan sus resultados; con base en ellos, se busca elevar una solicitud formal a la autoridad ambiental colombiana para que modifique el umbral de ruido permitido en torno a los autódromos.

El artículo aborda un problema contemporáneo que afecta a miles de ciudades del mundo: el ruido, específicamente, el ruido que generan las competencias de deportes a motor en los autódromos. Se esboza la situación de algunas pistas de diversos países que se han visto limitadas e, incluso, clausuradas por no cumplir con las normas de ruido exigidas por las autoridades ambientales. Tomando como marco teórico el control del ruido, se indaga en dos vertientes bien diferenciadas: el control pasivo del ruido y el control activo del ruido. Además y considerando que la normativa concerniente al ruido dista de ser homogénea a nivel internacional, se realiza una pesquisa inicial en ese sentido y se presentan sus resultados; con base en ellos, se busca elevar una solicitud formal a la autoridad ambiental colombiana para que modifique el umbral de ruido permitido en torno a los autódromos.

El artículo aborda un problema contemporáneo que afecta a miles de ciudades del mundo: el ruido, específicamente, el ruido que generan las competencias de deportes a motor en los autódromos. Se esboza la situación de algunas pistas de diversos países que se han visto limitadas e, incluso, clausuradas por no cumplir con las normas de ruido exigidas por las autoridades ambientales. Tomando como marco teórico el control del ruido, se indaga en dos vertientes bien diferenciadas: el control pasivo del ruido y el control activo del ruido. Además y considerando que la normativa concerniente al ruido dista de ser homogénea a nivel internacional, se realiza una pesquisa inicial en ese sentido y se presentan sus resultados; con base en ellos, se busca elevar una solicitud formal a la autoridad ambiental colombiana para que modifique el umbral de ruido permitido en torno a los autódromos.

El artículo aborda un problema contemporáneo que afecta a miles de ciudades del mundo: el ruido, específicamente, el ruido que generan las competencias de deportes a motor en los autódromos. Se esboza la situación de algunas pistas de diversos países que se han visto limitadas e, incluso, clausuradas por no cumplir con las normas de ruido exigidas por las autoridades ambientales. Tomando como marco teórico el control del ruido, se indaga en dos vertientes bien diferenciadas: el control pasivo del ruido y el control activo del ruido. Además y considerando que la normativa concerniente al ruido dista de ser homogénea a nivel internacional, se realiza una pesquisa inicial en ese sentido y se presentan sus resultados; con base en ellos, se busca elevar una solicitud formal a la autoridad ambiental colombiana para que modifique el umbral de ruido permitido en torno a los autódromos.

[EN] In this paper, we present a distributed affine projection (AP) algorithm for an acoustic sensor network where the nodes are acoustically coupled. Every acoustic node is composed of a microphone, a processor, and an actuator to control the sound field. This type of networks can use distributed adaptive algorithms to deal with the active noise control (ANC) problem in a cooperative manner, providing more flexible and scalable ANC systems. In this regard, we introduce here a distributed version of the multichannel filtered-x AP algorithm over an acoustic sensor network that it is called distributed filtered-x AP (DFxAP) algorithm. The analysis of the mean and the mean-square deviation performance of the algorithm at each node is given for a network with a ring topology and without constraints in the communication layer. The theoretical results are validated through several simulations. Moreover, simulations show that the proposed DFxAP outperforms the previously reported distributed multiple error filtered-x least mean square algorithm.

The aim of the thesis is to upgrade an existing Remote Laboratory for Active Noise Control (ANC) and acoustics experiments providing users with a more authentic real life experience. This is done by designing a solution that allows remote position control of microphones inside a ventilation duct for ANC experiments. The suggested features to be implemented substantially improve the flexibility of the existing remote laboratory, based on the Virtual Instrument System in Reality (VISIR) platform, as well as providing more control over the system as a whole. The work in the project may be divided into the following steps: theoretical design of mechanical and electrical parts of the system along with control algorithms which include a study of similar solutions and related work, implementation of designed system, subsequent testing of the system, connecting the implemented system to the equipment for remote communication and adding the appropriate features to the remote control interface.

The aim of the thesis is to upgrade an existing Remote Laboratory for Active Noise Control (ANC) and acoustics experiments providing users with a more authentic real life experience. This is done by designing a solution that allows remote position control of microphones inside a ventilation duct for ANC experiments. The suggested features to be implemented substantially improve the flexibility of the existing remote laboratory, based on the Virtual Instrument System in Reality (VISIR) platform, as well as providing more control over the system as a whole. The work in the project may be divided into the following steps: theoretical design of mechanical and electrical parts of the system along with control algorithms which include a study of similar solutions and related work, implementation of designed system, subsequent testing of the system, connecting the implemented system to the equipment for remote communication and adding the appropriate features to the remote control interface.

High quality noise and vibration measurements outside of a laboratory environment on real life structures and applications are not trivial. True boundary and operating conditions enforce unique challenges on the measurements. Measurements in hazardous situations such as high magnetic fields, and high temperature environments, etc., where ordinary measurement equipment and methods may not be employed, require further precautions. Post measurements objectives such as analysis, design and strategic decisions, e.g., control, rely heavily on the quality and integrity of the measurements (data). The quality of the experimental data is highly correlated with the on-field expertise. Practical or hands-on experience with measurements can be imparted to prospective students, researchers and technicians in the form of laboratory experiments involving real equipment and practical applications. However, achieving expertise in the field of sound and vibration measurements in general and their active control in particular is a time consuming and expensive process. Consequently most institutions can only afford a single setup, resulting in the compromise of the quality of expertise. In this thesis, the challenges in the field of sound and vibration measurements in high magnetic field are addressed. The analysis and measurement of vibration transferred from an operational magnetic resonance imaging (MRI) scanner to adjacent floors is taken as an example. Improvised experimental measurement methods and custom-made frequency analysis techniques are proposed in order to address the challenges and study the vibration transfer. The methods may be extended to other operational industrial machinery and hazardous environments. To encourage and develop expertise in the field of acoustic/vibration measurements and active noise control on practical test beds, remotely controlled laboratory setups are introduced. The developed laboratory setup, which is accessed and controlled via the Internet

High quality noise and vibration measurements outside of a laboratory environment on real life structures and applications are not trivial. True boundary and operating conditions enforce unique challenges on the measurements. Measurements in hazardous situations such as high magnetic fields, and high temperature environments, etc., where ordinary measurement equipment and methods may not be employed, require further precautions. Post measurements objectives such as analysis, design and strategic decisions, e.g., control, rely heavily on the quality and integrity of the measurements (data). The quality of the experimental data is highly correlated with the on-field expertise. Practical or hands-on experience with measurements can be imparted to prospective students, researchers and technicians in the form of laboratory experiments involving real equipment and practical applications. However, achieving expertise in the field of sound and vibration measurements in general and their active control in particular is a time consuming and expensive process. Consequently most institutions can only afford a single setup, resulting in the compromise of the quality of expertise. In this thesis, the challenges in the field of sound and vibration measurements in high magnetic field are addressed. The analysis and measurement of vibration transferred from an operational magnetic resonance imaging (MRI) scanner to adjacent floors is taken as an example. Improvised experimental measurement methods and custom-made frequency analysis techniques are proposed in order to address the challenges and study the vibration transfer. The methods may be extended to other operational industrial machinery and hazardous environments. To encourage and develop expertise in the field of acoustic/vibration measurements and active noise control on practical test beds, remotely controlled laboratory setups are introduced. The developed laboratory setup, which is accessed and controlled via the Internet

The aim of the thesis is to upgrade an existing Remote Laboratory for Active Noise Control (ANC) and acoustics experiments providing users with a more authentic real life experience. This is done by designing a solution that allows remote position control of microphones inside a ventilation duct for ANC experiments. The suggested features to be implemented substantially improve the flexibility of the existing remote laboratory, based on the Virtual Instrument System in Reality (VISIR) platform, as well as providing more control over the system as a whole. The work in the project may be divided into the following steps: theoretical design of mechanical and electrical parts of the system along with control algorithms which include a study of similar solutions and related work, implementation of designed system, subsequent testing of the system, connecting the implemented system to the equipment for remote communication and adding the appropriate features to the remote control interface.

This paper deals with nonlinear active noise control using adaptive wavelet filters. The ability of wavelets in signal reconstruction and function approximation make them appealing for black box system identification. Moreover, the intrinsic similarity between wavelet filters and noise/vibration signals implies that better approximation of these signals can be achieved by employing wavelet filters. Here, a new simple structure for using in active noise control system is proposed comprises a nonlinear static mapping cascaded with an IIR filter to take care of the dynamics of the system. With this strategy, one can avoid using multi-dimensional wavelet networks and thus eliminate curse of dimensionality. The performance of the proposed ANC system is examined for typical linear/nonlinear cases. The simulation results demonstrate superior performance of this method in terms of fast convergence rate and noise attenuation as well as computational complexity reduction while avoiding curse of dimensionality.

El artículo aborda un problema contemporáneo que afecta a miles de ciudades del mundo: el ruido, específicamente, el ruido que generan las competencias de deportes a motor en los autódromos. Se esboza la situación de algunas pistas de diversos países que se han visto limitadas e, incluso, clausuradas por no cumplir con las normas de ruido exigidas por las autoridades ambientales. Tomando como marco teórico el control del ruido, se indaga en dos vertientes bien diferenciadas: el control pasivo del ruido y el control activo del ruido. Además y considerando que la normativa concerniente al ruido dista de ser homogénea a nivel internacional, se realiza una pesquisa inicial en ese sentido y se presentan sus resultados; con base en ellos, se busca elevar una solicitud formal a la autoridad ambiental colombiana para que modifique el umbral de ruido permitido en torno a los autódromos.

The aim of the thesis is to upgrade an existing Remote Laboratory for Active Noise Control (ANC) and acoustics experiments providing users with a more authentic real life experience. This is done by designing a solution that allows remote position control of microphones inside a ventilation duct for ANC experiments. The suggested features to be implemented substantially improve the flexibility of the existing remote laboratory, based on the Virtual Instrument System in Reality (VISIR) platform, as well as providing more control over the system as a whole. The work in the project may be divided into the following steps: theoretical design of mechanical and electrical parts of the system along with control algorithms which include a study of similar solutions and related work, implementation of designed system, subsequent testing of the system, connecting the implemented system to the equipment for remote communication and adding the appropriate features to the remote control interface.

High quality noise and vibration measurements outside of a laboratory environment on real life structures and applications are not trivial. True boundary and operating conditions enforce unique challenges on the measurements. Measurements in hazardous situations such as high magnetic fields, and high temperature environments, etc., where ordinary measurement equipment and methods may not be employed, require further precautions. Post measurements objectives such as analysis, design and strategic decisions, e.g., control, rely heavily on the quality and integrity of the measurements (data). The quality of the experimental data is highly correlated with the on-field expertise. Practical or hands-on experience with measurements can be imparted to prospective students, researchers and technicians in the form of laboratory experiments involving real equipment and practical applications. However, achieving expertise in the field of sound and vibration measurements in general and their active control in particular is a time consuming and expensive process. Consequently most institutions can only afford a single setup, resulting in the compromise of the quality of expertise. In this thesis, the challenges in the field of sound and vibration measurements in high magnetic field are addressed. The analysis and measurement of vibration transferred from an operational magnetic resonance imaging (MRI) scanner to adjacent floors is taken as an example. Improvised experimental measurement methods and custom-made frequency analysis techniques are proposed in order to address the challenges and study the vibration transfer. The methods may be extended to other operational industrial machinery and hazardous environments. To encourage and develop expertise in the field of acoustic/vibration measurements and active noise control on practical test beds, remotely controlled laboratory setups are introduced. The developed laboratory setup, which is accessed and controlled via the Internet

© 2017 by the authors; licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/)., This work presents a practical active noise control system composed of distributed and collaborative acoustic nodes. To this end, experimental tests have been carried out in a listening room with acoustic nodes equipped with loudspeakers and microphones. The communication among the nodes is simulated by software. We have considered a distributed algorithm based on the Filtered-x Least Mean Square (FxLMS) method that introduces collaboration between nodes following an incremental strategy. For improving the processing efficiency in practical scenarios where data acquisition systems work by blocks of samples, the frequency-domain partitioned block technique has been used. Implementation aspects such as computational complexity, processing time of the network and convergence of the algorithm have been analyzed. Experimental results show that, without constraints in the network communications, the proposed distributed algorithm achieves the same performance as the centralized version. The performance of the proposed algorithm over a network with a given communication delay is also included.