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Acoustic data provide scientific and engineering insights in fields ranging from biology and communications to ocean and Earth science. We survey the recent advances and transformative potential of machine learning (ML), including deep learning, in the field of acoustics. ML is a broad family of techniques, which are often based in statistics, for automatically detecting and utilizing patterns in data. Relative to conventional acoustics and signal processing, ML is data-driven. Given sufficient training data, ML can discover complex relationships between features and desired labels or actions, or between features themselves. With large volumes of training data, ML can discover models describing complex acoustic phenomena such as human speech and reverberation. ML in acoustics is rapidly developing with compelling results and significant future promise. We first introduce ML, then highlight ML developments in four acoustics research areas: source localization in speech processing, source localization in ocean acoustics, bioacoustics, and environmental sounds in everyday scenes. [ABSTRACT FROM AUTHOR]

An acoustic analysis was made of the speech characteristics of individuals recorded before and during a prolonged stay in Antarctica. A computational model was used to predict the expected changes due to close contact and isolation, which were then compared with the actual recorded productions. The individuals were found to develop the first stages of a common accent in Antarctica whose phonetic characteristics were in some respects predicted by the computational model. These findings suggest that the phonetic attributes of a spoken accent in its initial stages emerge through interactions between individuals causing speech production to be incrementally updated. [ABSTRACT FROM AUTHOR]

This paper presents an investigation of monsoon-generated infrasound events recorded in Islamabad, Pakistan. The majority of these events originate from a specific azimuth band, pointing towards the Himalaya mountain range in the Indian subcontinent. Although the monsoon phenomenon is well-known to develop over the Bay of Bengal and the Arabian sea and enters Pakistan along the foothills of Himalayas and south-eastern areas of Sindh, Pakistan, the associated infrasound signals have a distinct frequency signature that differs from mountain-associated waves (MAW) and microbaroms. While MAW have a frequency of 0.015–0.1 Hz and microbaroms are found in the frequency band 0.13–0.35 Hz, the monsoon-associated signal is mostly observed in the frequency band 0.6–1.1 Hz. This research highlights the potential of studying monsoon-generated infrasound events as an unexplored area of research in the study of the atmosphere and an important weather phenomenon. The paper also reports a strong correlation between these events and rainfall precipitation, which could potentially benefit early weather warning systems, especially in the context of climate change. The MATLAB-based analysis tool, MatSeis, is used for the detection of infrasound events, and the data collected from a four-element seismic acoustic array with Chaparral Physics 50A sensors in Islamabad are analyzed from June to September in the years 2021 to 2022. Overall, this study highlights the significance of monitoring and analyzing monsoon-generated infrasound events in the region. • First time monsoon-generated infrasound events recorded at Islamabad, Pakistan. • Different from mountain-associated waves and microbaroms. • These signals are mostly observed in the frequency band 0.35–3.5 Hz. • These infrasonic signals have a strong correlation with rain precipitation. • Which may be useful for early weather warning systems. [ABSTRACT FROM AUTHOR]

Most of existing the dehazing methods have high computational complexity and poor dehazing quality. Therefore, a fast haze removal method based on the haze density classification prior is proposed. Haze density is reflected by the difference between maximum channel and minimum channel. Based on this, haze density prior (HDP) is proposed. The HDP can effectively distinction between mist image and dense haze image, and quickly estimate the atmospheric light veil. In addition, an optimized method for estimating atmospheric light using the mid-channel of haze image is proposed, which overcomes limitations of global atmospheric light. Our method can fast and efficiently recover clear image because there is no estimation of transmission map. Experiments show that the proposed method outperforms existing methods in haze removal, especially for dense haze images. Comparison of objective evaluation and running time shows that the proposed method is effective and real-time. [ABSTRACT FROM AUTHOR]

[Display omitted] • Importantly, we have tried to clearly show corroles complexes could be excellent photosensitizers due to their robust triplet excited states and singlet oxygen formation, and photocatalysts in driving chemical reactions. • We are providing a very comprehensive overview of the photophysics of corrole and intimately related systems, highlighting their potential as versatile materials for emerging technologies. • Many studies are described about elucidating the excited triplet and singlet oxygen, time-settled electron paramagnetic reverberation (TREPR) analysis of corrole systems. • We cover the uses of corrole systems as photocatalysts, photosensitizers, and biomolecule docking agents. • The systematic progress of nonlinear optical (NLO) properties of corroles is discussed. The scientific research field of corrole systems has witnessed an explosion of interest in recent years owing to unique optical and electronic properties that are very promising for various applications. This timely review gives a thorough treatment of the primary literature of the photophysics of corrole systems, with a specific spotlight on the impacts of solvents, pH, heavy atoms, core-metal insertion, dyads, and aggregation. The inventory of features is helping pave the way towards new advancements. Many studies have been carried out by focusing on elucidating the excited triplet and singlet state lifetimes, and time-settled electron paramagnetic reverberation (TREPR) analysis of corrole systems. Furthermore, our review covers the auspicious uses of corrole systems as photocatalysts, photosensitizers, and biomolecule docking agents. Finally, the systematic progress of nonlinear optical (NLO) properties of corroles is discussed. We are hereby providing a comprehensive overview of the photophysics of corrole and intimately related systems, highlighting their potential as versatile materials for emerging technologies. [ABSTRACT FROM AUTHOR]

A framework is developed to perform Fourier-domain timing analysis on X-ray light curves with gaps, employing Gaussian processes to model the probability distribution underlying the observed time series from which continuous samples can be drawn. A technique is developed to measure X-ray reverberation from the inner regions of accretion discs around black holes in the low-frequency components of the variability, on time-scales longer than can be probed employing standard Fourier techniques. This enables X-ray reverberation experiments to be performed using data from satellites in low-Earth orbit such as NICER, NuSTAR , and the proposed X-ray timing mission STROBE-X , and enables long time-scale reverberation around higher mass active galactic nuclei (AGNs) to be measured by combining observations. Gaussian processes are applied to observations of the broad line radio galaxy 3C 120 spanning two orbits with XMM–Newton to measure the relative time lags of successive X-ray energy bands. The lag–energy spectrum between 5 × 10−6 and 3 × 10−5 Hz, estimated using Gaussian processes, reveals X-ray reverberation from the inner accretion disc for the first time in this radio-loud AGN. Time lags in the relativistically broadened iron K line are significantly detected. The core of the line lags behind the continuum by (3800 ± 1500) s, suggesting a scale height of the corona of (13 ± 8)  r g above the disc. The ability to compare the structure of coronae in radio-loud AGNs to their radio-quiet counterparts will yield important insight into the mechanisms by which black holes are able to launch jets. [ABSTRACT FROM AUTHOR]

The primary goal of the Target and Reverberation Experiment in spring 2013 (TREX13) was to identify the major physical mechanisms responsible for midfrequency reverberation. While both the sea surface and seafloor can contribute to reverberation, the seafloor is typically dominant in shallow water environments. To determine the level of this contribution at the TREX13 site, the bottom backscatter sonar (BBS) was deployed from a dive boat at multiple locations around the site. The BBS consists of a source and a receiver mounted on a short bracket that is suspended above the seafloor to measure direct-path bottom backscatter at 3 kHz. Data near normal incidence were interpreted as bottom reflectivity, which was used to quantitatively explain the range-dependence of the sediment composition at the experiment site. Two factors restricted the estimates of the bottom backscatter strength to the minimum grazing angle of 21 $^\circ$ : the currents at the experiment site made it difficult to position the system close to the seafloor, and the shallow water depth resulted in sea surface scatter contaminating small angle bottom backscatter. From the measured backscatter strength and by utilizing available environmental data, initial models of scattering strength indicate that at the shallow grazing angles of importance to reverberation, the scattering on the sand ridges is dominated by roughness scattering while in the muddy areas of the ridge swales, volume scattering dominates. The volume scattering from these mud areas is significantly stronger than the roughness scattering on the ridges by as much as 10 dB and may explain the substantial fluctuations observed in the reverberation as a function of range. [ABSTRACT FROM AUTHOR]

Long-thin network topologies are useful in monitoring tunnels and bridges because of their linear structure. In this paper, we apply the long-thin concept to under-ice acoustic sensor networks in the Arctic Ocean. We develop an acoustic wave propagation model for the under-ice environments using the ray-tracing method. Specifically, we derive the reflection coefficients of plane acoustic waves penetrating from seawater to ice in a ray-based model. The impulse responses and transmission loss, including their dependencies on the communication range, are examined in the under-ice environment. Furthermore, to maximize the operational lifetime of the under-ice long-thin network, we optimize the network topology by integrating Monte Carlo simulations with a differential evolution technique. The optimization results are presented for long-thin sensor network scenarios under the Arctic sea ice. Computer simulations show that by optimizing the sensor locations in the long-thin topology, one can take advantage of the sound convergent and divergent effects of the under-ice acoustic channel. As a result, the energy consumption of the long-thin sensor network can be significantly reduced so that its operational lifetime can be extended in the Arctic environment. [ABSTRACT FROM AUTHOR]

Most human communication is carried by modulations of the voice. However, a wide range of cultures has developed alternative forms of communication that make use of a whistled sound source. For example, whistling is used as a highly salient signal for capturing attention, and can have iconic cultural meanings such as the catcall, enact a formal code as in boatswain’s calls or stand as a proxy for speech in whistled languages. We used real-time magnetic resonance imaging to examine the muscular control of whistling to describe a strong association between the shape of the tongue and the whistled frequency. This bioacoustic profile parallels the use of the tongue in vowel production. This is consistent with the role of whistled languages as proxies for spoken languages, in which one of the acoustical features of speech sounds is substituted with a frequency-modulated whistle. Furthermore, previous evidence that non-human apes may be capable of learning to whistle from humans suggests that these animals may have similar sensorimotor abilities to those that are used to support speech in humans. [ABSTRACT FROM AUTHOR]

In this paper, an analytic range-independent reverberation model based on the first-order perturbation theory is extended to range-dependent waveguide. This model considers the effect of bottom composite roughness: small-scale bottom rough surface provides dominating energy for reverberation, whereas large-scale roughness has the effect of forward and back propagation. For slowly varying bottom and short signal pulse, analytic small-scale roughness backscattering theory is adapted in range-dependent waveguides. A parabolic equation is used to calculate Green functions in range-dependent waveguides, and the orthogonal property of local normal modes is employed to estimate the modal spectrum of PE field. Synthetic tests demonstrate that the proposed reverberation model works well, and it can also predict the reverberation of range-independent waveguide as a special case. [ABSTRACT FROM AUTHOR]

Purpose: Normal-hearing and hard-of-hearing listeners suffer from reduced speech intelligibility in noisy and reverberant environments. Although daily listening environments are in constant motion, most researchers have only studied speech-in-noise perception for stationary masker locations. The aim of this study was to investigate the spatial release from masking (SRM) of circularly and radially moving maskers under different room acoustic conditions for young and elderly subjects. Method: Twelve young subjects with normal hearing and 12 elderly subjects with normal hearing or mild hearing loss were tested. Several different room acoustic conditions were simulated and reproduced via headphones using binaural synthesis. The target speech stream consisted of German digit triplets, and masker stream consisted of quasistationary noise with matched long-term averaged speech spectra. During the experiment, the position of the masker was changed to be in different stationary positions, or varied continuously. In the latter case, it was moved either on a circular trajectory spanning a 90° azimuth angle or on a radial trajectory linearly increasing the distance to the receiver from 0.5 m to 1.8 m. Absorption characteristics of the virtual room's surfaces were changed, recreating an anechoic room, a treated room with mean reverberation times (RT60) = 0.48 s, and an untreated room with mean RT60 = 1.26 s. Results: For the circular condition, a significant difference was found between moving and stationary maskers, F(4, 44) = 20.91, p < .001, with a bigger SRM for stationary maskers than moving masker conditions. Also, both age groups displayed a significant decrease in SRM over the reverberation conditions: F(2, 22) = 12.24, p < .001. For the radial condition, both age groups showed a significant decrease in SRM over the reverberation conditions, F(2, 22) = 13.62, p < .001, as well as the moving and stationary masker conditions, F(8, 88) = 29.23, p < .001. In general, the SRM of a moving masker decreased when the reverberation increased, especially for elderly subjects. Conclusions: A radially moving masker led to improved SRM in an anechoic environment for both age groups, whereas a circularly moving masker caused degraded SRM, especially for elderly subjects in the highly reverberant environment. [ABSTRACT FROM AUTHOR]

Inspecting abandoned mine shafts is critical in ensuring their safety through early identification of signs of deterioration. Since the common inspection methods of CCTV and LiDAR are not very effective underwater, two modules have been designed for inspecting the linings of flooded, abandoned mine shafts. Using sonar technology, they allow the early stages of degradation to the lining to be detected which – since this could be indicative of imminent collapse – provides protection against the consequential risk to property and human life. Detailed measurements of several shafts' cross-sections have been recorded using profiling and imaging sonar technology. Although imaging sonar provides very different results in the confined and reverberant environment of a mine shaft, compared to its more common environment of a seabed, it was shown that when combined with the profiling sonar, it allows shafts to be surveyed in a shorter period of time and improves the reliability of the profiling function. [ABSTRACT FROM AUTHOR]

Abstract Everyday communication takes place in the combined presence of reverberation and background noise, the latter having in some cases fluctuating characteristics and speech-like spectrum. To predict the speech intelligibility for fluctuating maskers, a time-frame implementation of the Speech Transmission Index (STI) in the indirect measurement scheme, named Extended STI (eSTI), has been recently proposed. Stationary speech spectrum noise is used as the probe signal and the a priori knowledge of the impulse response characterizing the transmission chain is required. A key issue of eSTI is the selection of the appropriate time frame for the calculations, whose duration is here assessed by a systematic experimental approach. Listening tests are developed for the scope, using speech-like stationary and fluctuating noises as maskers and rendering sound fields with various reverberation times and over a wide range of signal-to-noise ratios. An interval of frame durations providing equivalent values of eSTI under the two noises is identified. Within the target interval, statistically coincident psychometric curves are obtained for the two noises, thus ensuring that the same eSTI corresponds to the same speech intelligibility. [ABSTRACT FROM AUTHOR]

• Condensate drips from the split air conditioner are circulated along the room inner walls. • Cold energy from condensate is utilized to enhance the room cooling. • Increased cut off time of compressor of air conditioner unit. • Energy saving up to 8% and hence reduced energy cost. Cooling the room with Air Conditioner condensate drips is an energy saving measure. In tropical countries which have 70 to 80% Relative Humidity (RH) year round, the quantity of cool energy in the condensate is significant while room air conditioners are on. These defrost drips at about 10–15 °C is circulated along the inner walls of the room through copper tubes that absorbs the heat from the room walls and reduces the infiltration load. This in turn pre cools the room return air that results in reduction of run time of the air conditioner system, which ultimately reduces the energy consumption of the compressor. For given conditions of Air Conditioner(AC) unit, the condensate temperature, the run time, the return air temperature, supply air temperature and energy saved are tabulated and investigated before and after wall cooling using TEMPTROL Psychrometric software. The investigation reveals that around 6–8% energy savings are achieved through wall cooling. [ABSTRACT FROM AUTHOR]

In this paper an experimental method to quantify perceptual differences between acoustic stimuli is presented. The experiments are implemented as a signal-in-noise task, where two sounds are to be discriminated. By adjusting the signal-to-noise ratio (SNR) the difficulty of the sound discrimination is manipulated. If two sounds are very similar already, a low level of added noise (high SNR) makes the discrimination task difficult. For more dissimilar sounds, a higher amount of noise (lower SNR) is needed to affect discriminability. In other words, a strong correlation between SNR and similarity is expected. The experimental noises are generated to have similar spectro-temporal properties to those of the test stimuli. As a study case, the suggested method was used to evaluate recordings of one note played on seven Viennese pianos using (1) non-reverberant sounds (as recorded) and (2) reverberant sounds, where reverberation was added by means of digital convolution. The experimental results of the suggested method were compared with a similarity experiment using the method of triadic comparisons. The results of both methods were significantly correlated with each other. [ABSTRACT FROM AUTHOR]

Estimating regional evapotranspiration (ET) is challenging in data-limited regions where a lack of in situ observations constrain model calibration and implementation. Here we developed an ensemble mean surface energy balance (EnSEB) modeling framework that is independent of any ground calibration and applied it in India to understand the magnitude and variability of ET in this agriculturally important region. EnSEB uses daily land surface temperature (LST) and vegetation biophysical inputs from Moderate Resolution Imaging Spectroradiometer (MODIS) and climatic information from the National Aeronautics and Space Administration (NASA) Modern-Era Retrospective Analysis for Research and Applications, version 2 (Merra-2) products and runs seven surface energy balance (SEB) algorithms to estimate ensemble mean ET or latent heat (LE) fluxes at a spatial resolution of 1 km × 1 km. Due to limited access to observed flux data, we conducted three different types of model evaluation: i) instantaneous LE validation using observed SEB fluxes from Bowen ratio energy balance (BREB) measurements in four agroecosystems, ii) annual and seasonal ET comparison with six global products at the regional scale, and iii) by closing the basin-scale monthly water budget (WB) for five large river basins (87,900–312,812 km2) in India. Validation with the BREB measurements revealed hourly EnSEB LE estimates to be within 2% of the observed LE (R 2 = 0.57 and RMSE = 59 W m−2) and EnSEB was more accurate than any of the individual SEB models. Annual ET from EnSEB was positively correlated with six widely-used global ET products (r = 0.52–0.83, p-value < 0.001), but EnSEB captured the magnitude of ET in intensively irrigated regions much better. Basin-scale monthly WB miscloures were found to be between −1 and 9 mm month−1 from EnSEB ET estimates, which were better than those from the six global ET products. The gap filling method based on the constant ET r F (ET/reference ET) approach introduced some uncertainties in EnSEB, which presents room for future improvements. Overall, our results suggest that the automated and calibration-free multi-model EnSEB framework, which uses only remote sensing and readily available reanalysis data, has the ability to estimate ET with reliable accuracy in Indian agroecosystems. Such a framework could help us better understand and monitor the water cycle in regions where ground data are limited or non-existent. • A remote sensing based ensemble mean SEB (EnSEB) model was developed. • Integrating reanalysis data eliminated the need for ground observations. • EnSEB has moderately high R 2 and low bias when validated with ground LE fluxes. • Pixel and basin scale assessments of EnSEB showed promising results. • EnSEB ET maps will facilitate crop-climate interaction studies in data-limited regions. [ABSTRACT FROM AUTHOR]

In climate change science, the existence of a high degree of uncertainty seems to be the cause of anxiety for many scientists because it appears to undermine the authority of the science. One of the assertions made by the so-called sceptics against the scientific consensus on climate change is that because the science is so uncertain, there is no basis for taking action. The response of the climate change science community has been to develop in-depth analyses of uncertainty of increasing sophistication and complexity. In most areas of policy making, the normal situation is characterised by complexity, ambiguity and uncertainty. Therefore, dealing with uncertainty is not an unusual state of affairs for policy makers. However, the overemphasis given to uncertainty in the climate science discourse by scientists working in the field has been self-defeating as it has led to confusion among the intended recipients of the policy relevant scientific knowledge and allowed room for scepticism to grow. Climate change scientists should instead communicate and engage with policy makers (and the public) on those things that we know with confidence. [ABSTRACT FROM AUTHOR]

This paper searches the role of financial sector development in energy sector and therefore in climate changes in the case of developing and developed countries. Panel data ranging from 1960 to 2014 on an annual basis has been selected from 176 countries. Results suggest that carbon dioxide emissions in developed and developing countries are in long-term equilibrium relationship with financial sector; trade and finance sectors have long-term significant impacts on carbon emissions and therefore carbon emissions converge to their long-term equilibrium levels through the channels of finance and trade sectors. Impulse response analyses proved that finance and trade sectors have negative (reducing) impact on the emission levels in the case of developed economies while they have positive impact in the case of developing economies. These sectors exert significant effects on energy consumption of countries as well. Results confirm that developed countries are more successful in energy conservation policies compared to developing countries. Therefore, authorities in developing countries need to implement conservation policies effectively by mainly encouraging and supporting investments in alternative energy uses in order to prevent increases in emission levels through expansion in financial and trade sectors. [ABSTRACT FROM AUTHOR]

In order to solve the problem of instability of the traditional speech separation algorithm, a kind of reverberation speech separation model based on deep learning is proposed. The problem of speech separation in reverberation environment has been studied. The auditory scene analysis is used to simulate the human auditory perception ability. According to the ideal two value mode principle, the target speech signal can be extracted. Moreover, the deep neural network (DNN) shows great learning ability in speech recognition and artificial intelligence. In this paper, a DNN model is proposed to learn the inverse reverberation and denoising by learning the spectrum mapping between "contaminated" speech and pure speech. By extracting a series of spectrum features, the time dynamic information of adjacent frames is fused. The DNN is used to transform the coded spectrum, and restore the pure voice frequency spectrum. Finally, the time domain signal is reconstructed. In addition, the feature classification ability of DNN is also proposed to complete the separation of double sound reverberation speech. The binaural features ITD and ILD and the mono features GFCC are fused to form a long eigenvector. The DNN is pre-trained by RBM to complete the classification task. The results show that the proposed model improves the quality and intelligibility of the speech separation, and enhances the stability of the system significantly. [ABSTRACT FROM AUTHOR]

Windows are the only part of a building that can directly penetrate the solar radiation into the occupied space and thus the shading devices are needed to control the solar penetration. In the office buildings, they usually use external blinds and internal blinds to reduce heat gains during summer caused by sunlight as well as solar radiation. Therefore, these blinds are main part to maintain thermal comfort for office workers. The aim of this paper is to present results of measurements in four big office rooms in different situations of blinds application. Then, the influence of the internal and external blinds on the internal microclimate conditions inside the large offices during the hot summer days with high solar radiation will be evaluate. The offices floor area is from 43.3 m2 to 59.5 m2 and height 2.8 m. The experiments in this research were focused on measurement and evaluation of globe temperature, indoor air temperature and relative humidity at level of working place during several hot summer days. Comparison of the results of short-term measurements in a room with open blinds and closed blinds has shown the influence of the blinds on the reduction of indoor temperature. More significant was the effect of external aluminium blinds. Solar energies passing through the windows into the interior were 3,476 W without blind and 305 W in case of aluminium venetian external blinds. When the maximum outside temperature was 29.9 °C and office workers used blinds with natural ventilation, the maximum air temperatures in four rooms were from 27.2 °C to 28.5 °C, which exceeded maximum recommended temperature (28 °C). The external aluminium venetian blinds and internal fabric vertical blinds did not maintain thermal comfort inside the offices during all summer days, but it can help in reduction of energy consumption for air-conditioning. [ABSTRACT FROM AUTHOR]

Delta Modulation (DM) is a simple waveform coding algorithm used mostly when timely data delivery is more important than the transmitted data quality. While the implementation of DM is fairly simple and inexpensive, it suffers from several limitations, such as slope overload and granular noise, which can be overcome using Adaptive Delta Modulation (ADM). This paper presents novel 2-digit ADM with six-level quantization using variable-length coding, for encoding the time-varying signals modelled by Laplacian distribution. Two variants of quantizer are employed, distortion-constrained quantizer which is optimally designed for minimal mean-squared error (MSE), and rate-constrained quantizer, which is suboptimal in the minimal MSE sense, but enables minimal loss in SQNR for the target bit rate. Experimental results using real speech signal are provided, indicating that the proposed configuration outperforms the baseline ADM algorithms, including Constant Factor Delta Modulation (CFDM), Continuously Variable Slope Delta Modulation (CVSDM), 2-digit and 2-bit ADM, and operates in a much wider dynamic range. [ABSTRACT FROM AUTHOR]

• An RC model is developed based on CFD calculations for long-term predictions. • A well-designed heat sink can reduce risk of condensation on a PCB inside an enclosure. • The heat sink should be optimized based on operating and ambient conditions. Temperature and relative humidity are crucially important for the reliability of electronic devices in outdoor applications. For small enclosures, thermal control by a heat sink that is cooled by natural convection is the most widely used method. In this work, the functionality of a heat sink as a thermal mass for partially storing the heat that is generated by the electronics inside a typical electronics enclosure is studied using transient 3D CFD simulations. The stored energy is released with a time lag for the purpose of enhancing the stability of the local climate inside the enclosure. A typical enclosure is assumed to be exposed to Copenhagen outdoor conditions over a two-day time period. For fast and long term predictions, a Cauer ladder RC model is developed based on CFD simulation results. A correlation for calculating the Nusselt number representing heat transfer between the trapped air inside the enclosure and the heat sink is derived. Compared with CFD simulations, the RC model is found to predict slightly lower values for temperature, and slightly higher values for RH – given that the value of absolute humidity is quite constant over the timescales here, then the higher values of RH are largely due to the lower values of temperature. The lumped model correctly predicts the trend for temperatures and RH variations, however, suggesting that a properly calibrated RC model can be used for scoping calculations, and more importantly for long-term predictions. The method can be used for any other ambient and working conditions, as long as the temperature difference in the air does not exceed 25 [°C]. [ABSTRACT FROM AUTHOR]

Continuous long-term sound sources are recorded at hydroacoustic station H03S, a three-element hydrophone array south of Robinson Crusoe Island between 2014 April 23 and 2017 August 20. The origin of the signal between 3 and 20 Hz is investigated by using cross-correlation, array processing using plane wave beamforming and spectral analysis. One-bit normalization is successfully applied as a cross-correlation pre-processing step in order to suppress undesired earthquake events in the data. Traveltimes retrieved from averaged cross-correlations do not yield a coherent array direction of arrival. Averaged envelopes of the cross-correlations, however, indicate a coherent signal approaching H03S from a south–southwest direction. Beamforming indicates two dominant backazimuth directions: 172°–224° (Antarctica) and 242° (Monowai Volcanic Seamount). This continuous source field creates possibilities to investigate the applicability of acoustic thermometry at hydrophones H03 S1–S2. Cross-correlation and array processing indicate significant directional variation in local propagation, most likely related to the steep slope in the bathymetry near H03S. In addition, it is demonstrated that the ambient noise field is not sufficiently equipartitioned. It is shown that this causes a large error in the estimated temperature, primarily due to the short receiver spacing. These large errors have not been addressed in previous studies on deep-ocean acoustic thermometry. Hence, it is shown that acoustic thermometry does not perform well on small arrays such as H03S. The power spectral density yields a strong broadband signal in January–March, most likely related to iceberg noise. A narrow banded signal around 17 Hz between April and September corresponds to whale calls. The best-beam sound pressure levels towards Antarctica are compared to ERA5 climatologies for sea ice cover and normalized stress into the ocean, supporting the hypothesis of iceberg noise. [ABSTRACT FROM AUTHOR]

A study of the impact of reverberation on cruise regime acoustic testing of contra-rotating open rotors in a wind tunnel is presented. Models for the rotor tone noise generated in closed cross-section wind tunnels are derived and used in the analysis. The models account for rectangular and circular cross-sections, rigid or impedance boundaries and, for the rectangular wind tunnel case, the rotor axis may be arbitrarily located within the tunnel (but aligned with the flow direction). These models are used to generate simple simulations of model-scale open rotor testing in two real wind tunnels suited to high-speed rotor testing – the Transonic Wind Tunnel in Bedford, UK and the S1MA wind tunnel in Modane, France. In the analysis, the effect of various modelling parameters on the reverberant noise field is investigated. It is shown that open rotor interaction tone noise may be particularly susceptible to the impact of reverberation and that for many tones the reverberant field may persist and contribute to a contaminated noise field, even for wind tunnels with acoustic treatments on the walls of the working section. [ABSTRACT FROM AUTHOR]

The use of an underfloor air distribution (UFAD) system integrated with a chilled ceiling (CC) cooling system can provide a potentially advanced heating, ventilation, and air conditioning (HVAC) system with high sensible cooling loads in modern office buildings. In this paper, an experimental study of the impact of CC in a room with a high sensible cooling load with UFAD was performed when the chilled ceiling surface temperature increased from 17.0 to 26.0 °C. The vertical distributions of indoor air temperature, air velocity, and pollutant (CO2) concentration were measured and evaluated by the vertical air temperature difference (VATD), turbulence intensity (TI), and contaminant removal effectiveness (CRE), respectively. The results showed that the average VATD, TI, and CRE were 0.1–0.9 °C, 4–40%, and 0.85–1.19, respectively, when the internal and external sensible cooling loads equal 41.5W/m2. These evaluation indices varied clearly when the internal sensible cooling load increased from 41.5 to 69.5W/m2, whereas they were almost the same when the external sensible cooling load increased from 41.5 to 69.5W/m2. The minimum CRE and air diffusion performance index (ADPI) coincided with the maximum heat removal effectiveness (HRE) under a constant cooling load condition. The results suggest that it is better to balance the energy consumption as well as indoor air quality and thermal comfort in a room with UFAD + CC. [ABSTRACT FROM AUTHOR]

Abstract Adaptive multiple subfilters (MSF)-based algorithms have gained attention in recent times for their applications in acoustic echo cancellation (AEC). The most advanced combined-error MSF algorithm maintains a trade-off between the different-error and common-error subfilter-based algorithms, and it is employed for echo cancellation applications which need faster convergence. Variable tap-length adaptive filtering algorithms find the optimum filter length and are used for optimizing the tap-length of the subfilters in MSF-based echo cancellers. In case of a long room impulse response, the MSF-based variable tap-length algorithm achieves a pseudo-optimum tap-length, which renders the overall design undermodelled. Therefore, it becomes necessary to analyze the effects of the undermodelled adaptive filter on the performance of the variable tap-length MSF (VT-MSF)-based echo cancellers. In this paper, we present a mathematical investigation of convergence, steady-state MSE, stability and tracking capability of the VT-MSF echo cancellers having deficient tap-length adaptive subfilters. Simulation results are presented in support of the analysis for the VT-MSF algorithm for AEC. [ABSTRACT FROM AUTHOR]

In a lecture hall it is vital to assure proper teaching conditions meaning that the information from the speaker/teacher must be received correctly by the listeners. Speech intelligibility is the main objective when a lecture hall is evaluated. In this paper, the authors discuss the importance of the acoustics of a lecture hall and the influence of various parameters over speech transmission from the speaker – the professors to the listeners – the students. The number of acoustical parameters is very large, but Speech Transmission Index (STI) and Reverberation Time (RT) are commonly used to evaluate the acoustics of a teaching room. Other parameters like room geometry and seat placement have great influence in speech intelligibility. As an example, a lecture hall of 120 seats from Naval Academy „Mircea cel Batran“ is investigated using virtual simulations with ODEON software. The results of the simulations are discussed and some remarks are made regarding the current condition of the lecture hall. [ABSTRACT FROM AUTHOR]

There are two definitions of the inner product of modal spatial functions used in the literature. Both definitions integrate the product of the modal spatial functions over a line, area, or volume. The only difference is that one of the definitions takes the complex conjugate of one of the modal spatial functions before multiplying the modes together. The definitions are the same if the modal spatial functions are real. If the modal spatial functions are complex, only the definition which takes the complex conjugate is an inner product. If the specific acoustic impedance of the boundaries has a real part, then the modes are only orthogonal with the definition which does not take the complex conjugate, although this definition is not strictly an inner product because the modal spatial functions are complex in this situation. However, this definition of "inner product" can be used to calculate the coefficients in the modal expansion of the system response. On the other hand, when it comes to calculating the mean pressure squared and the mean sound intensity, the modal spatial functions cross-products cannot be ignored because the modes are not orthogonal for the definition which takes the complex conjugate. [ABSTRACT FROM AUTHOR]

The aim of this article is to study ways of highlighting presence and atmosphere in a concrete museum setting by means of H.U. Gumbrecht's presence theory, Gernot Böhme's definition of atmosphere and Madeleine Akrich's and Bruno Latour's script theory. The article is based on an exhibition experiment conducted at Faaborg Museum in Denmark where an artwork was exhibited in a temporary room with a door inviting visitors to enter one by one. The experiment was an attempt to highlight presence and atmosphere by de-scripting the museum's script. Twenty-one qualitative visitor interviews show that the enclosure was successful in turning the visitors' attention to the atmosphere of the museum space and the artwork itself. A significant number of visitors described in their own words their experience as a state of presence and these experiences were closely linked with the physical and social space of the museum. [ABSTRACT FROM AUTHOR]

The low-frequency properties of a room (where statistical methods in the standards cannot be applied directly) are often hard to estimate due to strong modal behaviour. The situation gets complicated by the fact that variations in the furnishing can have an impact on the modal patterns and therefore can also influence the results of measurements at certain points, in spite of the room properties being the same. The latter can hinder the achievement of acoustic comfort in dwellings, even if they comply with the current regulations, especially due to the fact that low-frequency noise is left outside the scope, since the standards currently in force do not require measurements below 100 Hz (albeit Sweden set 50 Hz as lower limit). This article aims to study variations of the sound field that results of varying the position of three moderately absorbing boards, which emulate how very sparse furniture can impact the sound field when relocated in the room. Furthermore, the potential of numerical models as prediction tools for such problems is pointed out. [ABSTRACT FROM AUTHOR]

Single channel speech enhancement is typically referred to the methods in which a filter is applied to the noisy speech to recover enhanced speech signal. In these methods, noise reduction causes speech distortion. So, it is a key concern to control the tradeoff between noise reduction and speech distortion in designing speech enhancement algorithms. This paper deals with the frequency domain single channel speech enhancement performed via short time furrier transform (STFT). Conventional frequency domain methods treat the STFT coefficients independently ignoring neighboring correlations. In this paper, we take into account neighboring correlations and derive a minimum variance distortionless response filter in the frequency domain. Experimental results show merits of our proposed method. [ABSTRACT FROM AUTHOR]

In speech-in-speech recognition, listeners' performance improves when spatial and linguistic properties of background and target speech differ. However, it is unclear if these benefits interact or whether they persist under reverberant conditions typical of indoor listening. To address these issues, these benefits were tested together in the presence and absence of reverberation. Results demonstrate that, in the anechoic condition, both spatial and linguistic benefits are obtained but they do not constrain each other. Under reverberation, only the spatial benefit was obtained. This demonstrates the critical need to consider reverberation effects in order to fully characterize the challenges of speech-in-speech listening. [ABSTRACT FROM AUTHOR]

The aim of this study is to explore the performance of binaural and monaural recordings in soundscape evaluation. Twelve sites with different acoustic scenarios were chosen, where binaural and monaural recordings were simultaneously made. Nine soundscape indicators were assessed by residents through a laboratory-based auditory test. The results showed that the two recording methods present good agreement on most soundscape evaluation indicators including overall impression, acoustic comfort, pleasantness, annoyance, eventfulness, and loudness. The two recording methods were found to be correlated with different indicators in a similar way. For most sites, the two recording methods were significantly correlated excluding for directionality. For both recording methods, the A-weighted sound pressure level was found to have a weak impact on soundscape evaluation. Reverberation time significantly affects reverberance through binaural recordings. Overall, for most soundscape indicators, it is feasible to use both recording methods, although when "realism," "reverberance," and "directivity" are involved in evaluation, binaural recordings will render corresponding perception more consistently than the monaural. [ABSTRACT FROM AUTHOR]

Enhancement to clean speech from noisy speech has always been a challenging issue for the researcher's community. Various researchers have used different techniques to resolve this problem. These techniques can be classified into the unsupervised and supervised approaches. Amongst the unsupervised approaches, Spectral Subtraction and Wiener Filter are commonly exploited. However, such approaches do not yield significant enhancement in the speech quality as well as intelligibility. As compared to unsupervised, supervised approaches such as Hidden Markov Model produces enhanced speech signals with better quality. However, supervised approaches need prior knowledge about the type of noise which is considered their major drawback. Moreover, for each noise type, separate models need to be trained. In this paper, a novel hybrid approach for the enhancement of speech is presented to overcome the limitations of both supervised and unsupervised approaches. The filter weights adjustment on the basis of Delta Learning Rule makes it a supervised approach. To address the issue of construction of new model for each noise type, the filter adjusts its weights automatically through minimum mean square error. It is unsupervised as there is no need of estimation of noise power spectral density. Various experiments are performed to test the performance of proposed filter with respect to different parameters. Moreover, the performance of the proposed filter is compared with state-of-the-art approaches using objective and subjective measures. The results indicate that CEGAF outperforms the algorithms such as Wiener Filter, supervised NMF and online NMF. [ABSTRACT FROM AUTHOR]

In this paper, a novel approach for the task of speech reverberation suppression in non-stationary (changing) acoustic environments is proposed. The suggested approach is based on the popular weighted prediction error (WPE) method, yet, instead of considering fixed reverberation prediction weights, our method takes into account the more generic time-varying autoregressive (TV-AR) model which allows dynamic estimation and updating for the prediction weights over time. We use an initial estimate of the prediction weights in order to optimally select the TV-AR model order and also to calculate the TV-AR coefficients. Next, by properly interpolating the calculated coefficients, we obtain the ultimate estimate of reverberation prediction weights. Performance evaluation of the proposed approach is shown not only for fixed acoustic rooms but also for environments where the source and/or sensors are moving. Our experiments reveal further reverberation suppression as well as higher quality in the enhanced speech samples in comparison with recent literature within the context of speech dereverberation. [ABSTRACT FROM AUTHOR]

In the field of room acoustics, it is well known that reverberation can be characterized statistically in a particular region of the time-frequency domain (after the transition time and above Schroeder's frequency). Since the 1950s, various formulas have been established, focusing on particular aspects of reverberation: exponential decay over time, correlations between frequencies, correlations between sensors at each frequency, and time-frequency distribution. In this paper, the author introduces a stochastic reverberation model, which permits us to retrieve all these well-known results within a common mathematical framework. To the best of the author's knowledge, this is the first time that such a unification work is presented. The benefits are multiple: several formulas generalizing the classical results are established that jointly characterize the spatial, temporal, and spectral properties of late reverberation. [ABSTRACT FROM AUTHOR]

This research is focused on rooms with a pair of parallel surfaces in which non-exponential reverberation energy decays are expected. An analytical model developed in a previous paper is first simplified and completed. It is based on the assumptions of geometrical room acoustics and the formalism of sound particles. The energy of the flux of sound particles emitted by the source in the room is evaluated by introducing some approximations. As a result, a simplified and intuitive model of the reverberation decay is obtained. This model is then extensively compared with reverberation decays computed by a sound ray program, for several kinds of rectangular rooms. A good agreement is obtained between corresponding decays and reverberation times T30. [ABSTRACT FROM AUTHOR]

Room acoustics parameters are typically predicted using some form of geometrical acoustics for large rooms. For smaller rooms, phased geometrical acoustics improves results for lower frequencies. The use of a spherical wave reflection coefficient improves the results further, yet the exact impact on room acoustics parameters is not fully known. This work predicts the reverberation time in medium-sized rooms (27 m3 < V < 300 m3) using phased geometrical acoustics. The difference between the use of plane and spherical wave reflection modeling is analyzed for a variety of boundary conditions, including non-uniform distribution of absorption. Since calculated differences are greater than the conventional just-noticeable-difference of 5% for reverberation time, laboratory listening tests are performed to confirm audibility of the modeled differences. Two narrow band noise stimuli (octave bands with central frequency 125 and 250 Hz) with a duration of 1 s were used for comparisons of 18 acoustic scenarios by means of a three-alternative forced choice method. More than half of the listeners could hear the differences in all 36 cases. Statistically significant results (chi-squared test was used) were found in two-thirds of the cases, corresponding to those with longer reverberation times. [ABSTRACT FROM AUTHOR]

Binaural auralization through proper room-acoustic simulation can produce a realistic listening experience as if the listener were sitting in a room with spatial perception, including enveloping reverberance. Based on analysis of experimentally measured binaural room-acoustic data, this paper discusses an approach to creating artificial but natural-sounding reverberation for binaural rendering that can be employed in simulating such an environment in an efficient way. Approaches to adjusting the spaciousness of enveloping reverberance within the context of artificially generated reverberation are investigated via hearing tests. This paper exploits the excellent pseudorandom properties of maximum-length sequences to generate deterministic and controllable decorrelations between binaural channels for artificial reverberation for room-acoustic simulations with high computational efficiency. To achieve natural-sounding enveloping reverberance in an enclosed space, and thereby an immersive environment, the shapes of both the reverberation energy decays and the spatial characteristics are found to be decisive. This paper discusses systematic hearing test results that support the mentioned finding. [ABSTRACT FROM AUTHOR]

Measured values of acoustic absorption obtained from standardized reverberation-chamber measurements often differ across laboratories. These discrepancies arise due to non-isotropic sound incidence on the absorbing specimen, diffraction at the sample edges, and differences in the chambers' shapes and dimensions. The present study examines an experimental method for characterizing the distribution of sound incidence on the specimen in the steady state. The methodology relies on a plane wave decomposition (i.e., estimation of the wavenumber spectrum) to determine the magnitude of the sound waves arriving from definite directions onto the absorbing sample. Based on this decomposition, the sound pressure, particle velocity, and sound intensity can be reconstructed in the vicinity of the absorbing specimen. One can distinguish between the incident and reflected components of the sound field, making it possible to characterize the incident energy flows. Measurements with a programmable robotic arm are conducted in a reverberation chamber in two damping conditions (empty and with absorption on the floor). The quantitative accuracy of the method is examined via an estimation of the sample's angle-dependent absorption coefficient, showing good agreement with theoretical predictions. It is anticipated that the proposed method will be of value in explaining the deviations encountered across standardized laboratories. [ABSTRACT FROM AUTHOR]