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This paper presents the results of a listening experiment designed to assess annoyance and perceived loudness (PL) for several unmanned aircraft system (UAS) operations, with the listener simulated in indoor and outdoor positions. This research investigated (i) how participant responses change depending on UAS operation, (ii) which broadband metrics are most suitable for representing annoyance and PL, (iii) differences in noise level required to result in equal participant responses to different operations, and (iv) which sound quality metrics (SQMs) are significant for UAS noise perception. Results indicate annoyance and PL responses were greatest for landing operations with flyovers being the least annoying or loud. LAeq, LASmax, and loudness (N5) were the strongest predictors in representing annoyance. Offset analysis predicted small differences in annoyance responses between flyovers and other operations, but also indicated that flyovers would require an increase to LASmax of 3.3 to 6.3 dB compared to other operations to achieve equal PL. Loudness was the most significant SQM, with minor contributions from impulsivity for annoyance and PL when outside, and tonality for PL when indoors. These findings contribute to the understanding of UAS noise perception for the development of metrics and assessment methods accounting for the characteristics of UAS operations. [ABSTRACT FROM AUTHOR]

Acoustic events exceeding a certain threshold of intensity cannot benefit from a linearization of the governing wave equation, posing an additional burden on the numerical modelling. Weak shock theory associates nonlinearity with the generation of high frequency harmonics that compensate for atmospheric attenuation. Overlooking the persistence of this phenomenon at large distances can lead to mispredictions in gun detection procedures, noise abatement protocols, and auditory risk assessment. The state-of-the-art mostly addresses aircraft jet noise, a stationary and largely random type of signal. The extension of such conclusions to muzzle blasts requires caution in considering their peculiar impulsive and broadband nature. A methodology based on the time and frequency analysis of an experimental dataset of eight calibres intends to find quantitative metrics linked to acoustic nonlinearity in outdoor muzzle blast propagation. Propagating three waveforms (SCAR-L 7.62 mm, Browning 9 mm, and Howitzer 105 mm) up to 300 [m] with the in-house numerical solver based on the nonlinear progressive wave equation, demonstrates that the propagation does not downgrade to truly linear. [ABSTRACT FROM AUTHOR]

Computational models are used to predict the performance of human listeners for carefully specified signal and noise conditions. However, there may be substantial discrepancies between the conditions under which listeners are tested and those used for model predictions. Thus, models may predict better performance than exhibited by the listeners, or they may "fail" to capture the ability of the listener to respond to subtle stimulus conditions. This study tested a computational model devised to predict a listener's ability to detect an aircraft in various soundscapes. The model and listeners processed the same sound recordings under carefully specified testing conditions. Details of signal and masker calibration were carefully matched, and the model was tested using the same adaptive tracking paradigm. Perhaps most importantly, the behavioral results were not available to the modeler before the model predictions were presented. Recordings from three different aircraft were used as the target signals. Maskers were derived from recordings obtained at nine locations ranging from very quiet rural environments to suburban and urban settings. Overall, with a few exceptions, model predictions matched the performance of the listeners very well. Discussion focuses on those differences and possible reasons for their occurrence. [ABSTRACT FROM AUTHOR]

This article, published in the Journal of the Acoustical Society of America in 2024, discusses the history and impact of noise pollution research. The author, Schultz, reviews social surveys conducted between the 1950s and 1975 to assess the annoyance caused by various sources of noise, such as aircraft, street traffic, expressway traffic, and railroads. Schultz finds that the results of 11 surveys show consistent levels of annoyance and proposes that the average of these curves is the best predictor of community annoyance due to transportation noise. Schultz's work has had a significant impact on noise assessment, with the day-night average sound level (DNL) becoming the accepted noise metric and the percentage of highly annoyed individuals becoming the accepted noise descriptor. Despite some criticism and skepticism, Schultz's simplification of noise assessment has become the basis for current standards on environmental noise assessment. [Extracted from the article]

The sound propagating in a turbulent atmosphere fluctuates in amplitude and phase. This phenomenon, known as acoustic scintillation, is caused by random fluctuations in the acoustic refractive index of the air induced by atmospheric turbulence. Auralization techniques should consider this phenomenon to increase the realism of the synthetic sound. This paper proposes a physics-based formulation to model sequences of log-amplitude and phase fluctuations of a sound propagating in a turbulent atmosphere. This method applies to slanted and vertical propagation of the sound, which is useful for simulating elevated noise sources such as aircraft, drones, and wind turbines. The theoretical framework is based on the spatial correlation functions for the log-amplitude and phase fluctuations for spherical waves, the von Kármán spectrum, and similarity theories to model atmospheric turbulence. Two applications with audio files are presented to demonstrate the applicability of this method to tonal and broadband noise. [ABSTRACT FROM AUTHOR]

As subsonic jets remain one of the major contributions to aircraft noise emissions, near-field flow simulations should be included in aircraft design at an early stage using quantitatively predicted sound pressure levels and the time-domain signal properties of the noise data. In this regard, the interface from the near-field data to the far-field radiation—under consideration of acoustic reflections from objects such as fuselage and wings—remains as bottleneck. This study presents the computation of a spherical equivalent source model of jet noise with minimal complexity by means of spherical harmonic (SH) coefficients. Using spherical Hankel extrapolation of sound pressure data from virtual, concentrical microphone arrays, the results of the determination for the radius, in which all acoustic sources of a flow field are confined, indicate the source radius around the end of the potential core to be equivalent to five times the nozzle diameter. The result of the SH transform shows the dominant energy contribution to be related to nine elementary sources. The resulting equivalent source model of jet noise provides a convenient format for further use in large-scale computational fluid dynamics simulations. [ABSTRACT FROM AUTHOR]

This article analyzes aircraft noise measurements from the Airbus A321neo at 7.5 and 5 nautical miles from the runway threshold. Using correlation, analysis of variance, and hierarchical regression analysis, we assessed the influence of flight data recorder variables and meteorological parameters on the measured sound level variations. A combination of aircraft speed and configuration of the high lift devices can predict approximately 60% of the sound level variations. Sound level dependence on speed ranges between 0.5 and 1.5 dB/10 kn for different configurations and landing gear deployment had a +3 dB impact on sound levels. At the same time, weather and wind conditions accounted for a relatively small proportion of the variation. Overall, this study sheds light on the factors contributing to aircraft noise during the final approach and provides insights into potential noise reduction strategies. [ABSTRACT FROM AUTHOR]

The nonlinear evolution of high-amplitude broadband noise is important to the psychoacoustic perception, usually annoyance, of high-speed jet noise. One method to characterize the nonlinear evolution of such noise is to consider a characteristic nonlinear waveform distortion length for the signal. A common length scale for this analysis is the shock formation distance of an initially sinusoidal signal. However, application of this length scale to broadband noise, even with the amplitude and source frequency replaced with characteristic values, may lead to underestimates of the overall nonlinear waveform distortion of the noise as indicated by the skewness of the time derivative of the acoustic pressure (or derivative skewness). This paper provides an alternative length scale derived directly from the evolution of the derivative skewness of Gaussian noise that may be more appropriate when analyzing the nonlinear evolution of broadband noise signals. This Gaussian-based length scale is shown to be a useful metric for its relative consistency and its physical interpretation. Various analytical predictions of the evolution of the derivative skewness for an ensemble of numerical simulations of noise propagation are used to highlight various aspects of this new length scale definition. [ABSTRACT FROM AUTHOR]

While sound emergence is used in several countries to regulate wind energy development, there is no published evidence that it is a relevant noise descriptor for this purpose. In the present work, we carried out two listening tests to evaluate the merits of sound emergence. Three definitions of sound emergence were considered: the one in ISO 1996-1, sound emergence under audibility condition eUAC, and spectral emergence eSP. We also considered the specific to residual ratio and loudness metrics. In each listening test, the sound stimuli consisted of 48 sound stimuli at three A-weighted sound pressure levels {30, 40, 50} dB and four specific-to-residual ratios { − 10 , − 5 , 0 , + 5 } dB. The results lead to the conclusion that short term annoyance is better predicted by the total sound pressure level than by sound emergence, whatever the definition considered for the latter, or than by the specific to residual ratio. Short-term annoyance is slightly better predicted by eUAC than by e, while e is a better predictor than eSP. The total sound pressure level and the loudness metrics performed similarly. Furthermore, the results provide evidence that sound emergence is a poor predictor of the audibility of wind turbine sounds. [ABSTRACT FROM AUTHOR]

It is hypothesized that sound quality metrics, particularly loudness, sharpness, tonality, impulsiveness, fluctuation strength, and roughness, could all be possible indicators of the reported annoyance to helicopter noise. To test this hypothesis, a psychoacoustic test was conducted in which subjects rated their annoyance levels to synthesized helicopter sounds. After controlling for loudness, a previous analysis using linear regression identified sharpness and tonality as important factors in predicting annoyance, followed by fluctuation strength. The current work focuses on multilevel regression techniques in which the regression slopes and intercepts are assumed to take on normal distributions across subjects. The importance of each metric is evaluated, and the variation of regression parameters among subjects is evaluated using simple models. Then more complete models are investigated, which include the combination of selected metrics and subject-specific effects. While the conclusions from linear regression analysis are affirmed by multilevel analysis, other important effects emerge. In particular, subject-specific intercepts are shown to be more important than subject-specific slopes. In addition, subject-specific slopes for fluctuation strength and sharpness are more important than for tonality. Using a multilevel framework, the relative importance of sound quality metrics is reexamined, and the potential for modeling human annoyance to helicopter noise based on sound quality metrics is explored. [ABSTRACT FROM AUTHOR]

Phased microphone array methods are increasingly used to localize and quantify noise sources of aircraft under flight condition. However, beamforming results suffer from loss of image resolution and corruption of sound levels due to atmospheric turbulence causing coherence loss between microphones. A synthesis method is presented that reproduces these effects in a virtual environment. Sound propagation through turbulent atmosphere is described by models by Ostashev and Wilson and by von Kármán turbulence spectra. Spatial coherence is calculated based on the parabolic equation for statistically inhomogeneous, isotropic turbulence. Decorrelation of signals is achieved by time-varying mixing of mutually independent signals with identical PSD based on coherence factors. The concept of auralization is employed to account for propagation delay, geometrical spreading, Doppler effect, air absorption, and ground effect. The application is demonstrated for a virtual 56 m aperture microphone array. The impact of different meteorological conditions on the beamforming and deconvoluted results are presented. For increasing turbulence strength, the results show decreasing sound levels and increasingly blurred images. The proposed method allows us to reproduce the effects of turbulence-induced coherence loss in phased microphone array measurements and to optimize array designs and algorithms in a virtual, controllable environment. [ABSTRACT FROM AUTHOR]

Miller, Czech, Hellauer, Nicholas, Lohr, Jodts, Broene, Morganstein, Kali, Zhu, Cantor, Hudnall, and Melia [(2021). HMMH Report 308520.004.001] reported the findings of a 20-airport social survey sponsored by the U.S. Federal Aviation Administration that had been designed and conducted six years earlier. Their primary analyses yielded FICON (1992) style (national average and airport-specific bivariate logistic regression) functions relating aircraft noise exposure to the prevalence of high annoyance [FICON (1992). "Federal agency review of selected airport noise analysis issues" (Department of Defense, Washington, DC)]. Alternate analyses of these field observations offer pragmatic benefits for regulatory purposes. Community Tolerance Level (CTL) analysis yields a national average exposure-response predictive function that is nearly indistinguishable from that of a bivariate logistic regression function. Since it natively distinguishes dose-related from collective, non-dose influences on annoyance, it also permits a more parsimonious and readily understood account of the association between aircraft noise exposure and annoyance. Within the exposure range of primary contemporary regulatory concern, CTL analysis accounts for as much variance as FICON-style analysis in the association between noise exposure and predicted annoyance; provides a causal basis for regulation; and can be more effectively implemented and defended than a purely correlation-based analysis. In addition, CTL analysis helps to address the substantial disagreement between the findings of the literature and those of national and international technical consensus standards. [ABSTRACT FROM AUTHOR]

Exposure to noise occurs throughout daily life and, depending on the intensity, duration, and context, can lead to hearing loss, disturbed sleep, decreased academic achievement, and other negative health outcomes. Recently, smartwatches that use the device's onboard microphone to measure noise levels were released. This study evaluated the accuracy of these smartwatches in a controlled laboratory setting. For broadband pink noise, a total of 11 441 measurements were collected. The results showed that, on average, the smartwatch reported 3.4 dBA lower than the reference system on average. For the octave-band, a total of 18 449 measurements were collected. The smartwatch measured lower than the reference microphone from the 125 Hz to 1000 Hz octave bands, were somewhat in agreement at 2000 Hz, measured higher sound pressure levels than the reference microphone at 4000 Hz, and then lower at 8000 Hz. Despite not meeting the ANSI criteria for sound level meters, in some cases, these smartwatches still provide a reasonable degree of accuracy and have the potential for use in studies that require the measurement of personal noise exposure over an extended period. [ABSTRACT FROM AUTHOR]

Unmanned aerial vehicles are rapidly advancing and becoming ubiquitous in an unlimited number of applications, from parcel delivery to people transportation. As unmanned aerial vehicle (UAV) markets expand, the increased acoustic nuisance on population becomes a more acute problem. Previous aircraft noise assessments have highlighted the necessity of a psychoacoustic metric for quantification of human audio perception. This study presents a framework for estimating propeller-based UAV auditory detection probability on the ground for a listener in a real-life scenario. The detection probability is derived by using its free-field measured acoustic background and estimating the UAV threshold according to a physiological model of the auditory pathway. The method is presented via results of an exemplar measurement in an anechoic environment with a single two- and five-bladed propeller. It was found that the auditory detection probability is primarily affected by the background noise level, whereas the number of blades is a less significant parameter. The significance of the proposed method lies in providing a quantitative evaluation of auditory detection probability of the UAV on the ground in the presence of a given soundscape. The results of this work are of practical significance since the method can aid anyone who plans a hovering flight mode. [ABSTRACT FROM AUTHOR]

Current best-practice aircraft noise calculation models usually apply a so-called lateral attenuation term, i.e., an empirical formula to account for sound propagation phenomena in situations with grazing sound incidence. The recently developed aircraft noise model sonAIR features a physically based sound propagation core that claims to implicitly account for the phenomena condensed in this correction. The current study compares calculations for situations with grazing sound incidence of sonAIR and two best-practice models, AEDT and FLULA2, with measurements. The validation dataset includes on the one hand a large number of commercial aircraft during final approach and on the other hand departures of a jet fighter aircraft, with measurement distances up to 2.8 km. The comparisons show that a lateral attenuation term is justified for best-practice models, resulting in a better agreement with measurements. However, sonAIR yields better results than the two other models, with deviations on the order of only ±1 dB at all measurement locations. A further advantage of a physically based modeling approach, as used in sonAIR, is its ability to account for varying conditions affecting lateral attenuation, like systematic differences in the temperature stratification between day and night or ground cover other than grassland. [ABSTRACT FROM AUTHOR]

Health Canada, in collaboration with Advanis, conducted the Canadian Perspectives on Environmental Noise Survey (CPENS) to investigate expectations and attitudes toward environmental noise in rural and non-rural Canada. The CPENS, a 26-item questionnaire, was completed online by 6647 randomly selected Canadians, age 18 y and older between April and May 2021. The prevalence of reporting their area as often or always calm, quiet, and relaxing was 76.8%, 64%, and 48.4% in rural/remote, suburban, and urban, respectively. A high expectation of quiet was less prevalent yet followed the same pattern: rural/remote (58.2%), suburban (37.4%), and urban (21.8%). Self-reported health status and noise sensitivity were unrelated to geographic region. A high magnitude of non-specific sleep disturbance over the previous 12 months was reported by 7.8% overall; highest among urban dwellers (9.8%), followed by suburban (7.2%) and rural/remote (5.5%) dwellers (p < 0.01). High annoyance toward road traffic noise was 8.5% overall, and significantly higher in urban (10.5%), relative to suburban (7.9%) and rural/remote (6.6%) areas (p < 0.0001). Annoyance toward noise from rail, aircraft, mining, industry, marine activity, construction, wind turbines, and landscaping equipment is reported. The analysis also explores potential differences between Indigenous Peoples of Canada and non-Indigenous Canadians in their attitudes and expectations toward environmental noise. [ABSTRACT FROM AUTHOR]

Modern apartments in major cities are usually made of lightweight structures with inadequate acoustic properties, leading to a growing number of noise complaints by residents of inadequate sound insulation in high-rise buildings. When a toilet is flushed, loud and irregular sounds like humming, gurgling, or bubbling, "explosive" fury from vacuum-assisted toilets are generated. Though these toilet flushing sounds are not very harmful, they can still be perceived as nuisances by users nearby. The toilet flushing noise has posed a serious concern among apartment occupants and adjacent residents, causing health problems like sleep disturbance and irritation. In this study, the psychoacoustical investigations have been performed in four stages. In the first stage, the toilet flushing noise was recorded for several toilets with two designs: a close-coupled floor-mount toilet and a back-to-wall mount toilet. The second stage evaluated the physical and psychoacoustical characteristics of those recorded flushing sounds using psychoacoustic analysis software. The noise qualities were determined in the third stage by assessing autocorrelation function/interaural cross correlation function factors from the post-processed recorded sound data. Finally, we designed and successfully demonstrated an innovative acoustic meta-absorber prototype for mitigating the toilet flushing noise. The results have revealed a significant reduction in loudness because of meta-absorbers. [ABSTRACT FROM AUTHOR]

Carr, Davies, Loubeau, Rathsam, and Klos [J. Acoust. Soc. Am. 148, 414–429 (2020)] found that indoor annoyance caused by sonic booms may be predicted from the A-weighted sound exposure level and the heaviness of the booms. Moreover, they suggest that, irrespective of the outdoor-to-indoor sound reduction, indoor annoyance may be predicted from outdoor sound levels. The present paper shows that their data to some extent also support a model in which the contribution of heaviness is level-dependent and that data reported in the literature point out that it is unlikely that indoor annoyance is independent of the degree of façade attenuation. [ABSTRACT FROM AUTHOR]

This paper presents an atmospheric propagation model, based on ray acoustics, that accounts for realistic weather conditions in the evaluation of the noise footprint of an aircraft. Noise sources, obtained using the Ffowcs Williams and Hawkings acoustic analogy applied to scale-resolved flow simulation data, are stored on a hemisphere surrounding the vehicle. These noise sources are propagated using a propagation model that takes into account the vertical variability of air temperature and wind velocity. The electric vertical takeoff and landing aircraft, presented by Casalino, van der Velden, and Romani [(2019). in Proceedings of the AIAA Scitech 2019 Forum, January 7–11, San Diego, CA, pp. 1834–1851], is used as a case study; noise footprints, obtained considering various vertically varying temperature and wind velocity distributions, are compared. It is shown that weather conditions in the acoustic wave propagation can contribute to mismatch up to 4 dBA in the illuminated zone and a significant drop in the refractive shadow zone caused by the vertical air temperature and wind velocity gradients. This work constitutes the first accomplishment in including realistic atmospheric effects in aircraft community noise prediction based on scale-resolved flow simulations. [ABSTRACT FROM AUTHOR]

This paper deals with the question of how specific weather conditions affect the perception of aircraft noise. Auralization is a suitable method by enabling parametrical decompositions of the overall aircraft noise scenario into source and propagation components. Considering influences on the auditory perception, the signal processing chain contains different virtual receivers and post processing using psychoacoustic hearing models. For broad coverage, generic standardized as well as measurement-based atmosphere models with variation of ground impedances such as soil data are evaluated. These variations are given aircraft noise measurement values based on A-weighted sound pressure levels L A and psychoacoustic measures regarding loudness, N, and sharpness, S. The results show an immense influence of weather conditions on A-weighted sound pressure levels and on psychoacoustic perception of aircraft noise, too. The weather-dependent differences of A-weighted sound pressure levels are up to 15 dB A and relative differences regarding loudness of factor 1.6 and sharpness of factor 2.0 occur. The approach can be used to get a better understanding of how the temporal statistics of specific local weather conditions and their perceptual consequences may lead to improved taxation of actual noise events and to an improved basis for long-term averages of aircraft noise effects. [ABSTRACT FROM AUTHOR]

Peru declared a state of emergency on March 16 in order to prevent SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2) transmissions; thus, the International Airport was closed and the soundscape of urban zones under the flight tracks have been changed in view of the fact that airplane traffic was suspended. The authors have been conducting noise monitoring since February and because of that sufficient noise data for knowing the soundscape before and during the lockdown were obtained. This article presents a case of aircraft annoyance noise in one of Lima's city districts, which is near the aircraft climbing curve, toward the ocean on departure from Lima. [ABSTRACT FROM AUTHOR]

The European Region of the World Health Organization (WHO) recently published revised recommendations for transportation noise exposure intended to limit adverse health effects. WHO's newly recommended "safe" limit for aircraft noise exposure is about an order of magnitude lower than the limits currently adopted by most European countries. WHO defines "safe exposure" as the level corresponding to an annoyance prevalence rate of 10% highly annoyed. The revised recommendations are based on a limited selection of post-2000 publications. About half of the cited studies rely on nonstandard questionnaires, respondent selection, and definitions of annoyance prevalence rates which over-estimate annoyance. A re-analysis of a larger and more representative selection of studies that relies on standard procedures shows that no meaningful changes in prevalence rates of high annoyance with aircraft noise have occurred and that existing evidence does not support WHO's revised recommendations. [ABSTRACT FROM AUTHOR]

Noise from a tactical aircraft can impact operations due to concerns regarding military personnel noise exposure and community annoyance and disturbance. The efficacy of mission planning can increase when the distinct, complex acoustic source mechanisms creating the noise are better understood. For each type of noise, equivalent acoustic source distributions are obtained from a tied-down F-35B operating at various engine conditions using the hybrid method for acoustic source imaging of Padois, Gauthier, and Berry [J. Sound Vib. 333, 6858–6868 (2014)]. The source distributions for the distinct noise types are obtained using different sections of a 71 element, ground-based linear array. Using a subarray close to the nozzle exit plane, source distributions are obtained for fine-scale turbulent mixing noise and broadband shock-associated noise, although grating lobes complicate interpretations at higher frequencies. Results for a subarray spanning the maximum sound region show that the multiple frequency peaks in tactical aircraft noise appear to originate from overlapping source regions. The observation of overlapping spatial extent of competing noise sources is supported by the coherence properties of the source distributions for the different subarrays. [ABSTRACT FROM AUTHOR]

Usually the prediction of airfoil-gust interaction noise is mainly based on the flat plate solution, and only the transverse velocity disturbance that is perpendicular to the flat plate surface is considered. However, the solution might underestimate the sound generation in non-uniform mean flows for finite thickness airfoils, in which the velocity disturbance in the streamwise direction could probably produce sound as well. The effect is studied in this work by using both numerical simulations and theoretical analysis. To highlight the effect of streamwise disturbance, the anisotropic turbulences with constant transverse velocity components while varying streamwise components are employed, which can be realised by adjusting the integral length scales in the Gaussian energy spectra. The simulation results explicitly show that more sound is produced by the streamwise components for airfoils at higher Mach numbers when the flow non-uniformities are more significant. An analytical model based on acoustic analogy to account for the sound generation by the coupling between the gust and non-uniform mean flows is proposed, which explains the observations in the numerical simulation well. Also, a correction to Amiet's flat plate solution using the proposed model yields better agreement with the numerical results, especially for anisotropic turbulences with larger integral length scale in the streamwise direction. [ABSTRACT FROM AUTHOR]

Annoyance due to urban road traffic noise combined with aircraft noise was studied using both laboratory and field survey data. Laboratory data were used to propose (i) partial annoyance models considering psychoacoustic indices and noise sensitivity, and (ii) total annoyance models considering noise indices or partial annoyance models. To predict partial and total annoyance in field, a methodology was proposed to estimate the different psychoacoustic indices, involved in annoyance models, from Ldenvalues. This methodology, interesting from a practical point of view, and the proposed annoyance models enable a good prediction of the field partial and total annoyance ratings compared to models based on Lden only. These results show that there is a need to develop the methodology of psychoacoustic index estimation from noise map Lden and also partial and total annoyance models. [ABSTRACT FROM AUTHOR]

Helicopter noise exhibits distinctive acoustical characteristics (e.g., pulsation) compared to noise from propeller-driven aircraft which contains tonal components. Whereas, at comparable sound exposure levels (LAE), annoyance reactions to these sources might be different, knowledge of potential annoyance differences is scarce. This paper reports a comparison between short-term annoyance reactions to noise from light-weight helicopters and propeller-driven aircraft in a laboratory setup. Stimuli were presented with a 3D sound reproduction system in a listening test facility based on field recordings of takeoffs and landings. Propagation filtering and amplitude changes were carried out to simulate various propagation distances and source levels, covering a reasonable LAE range from 64 to 85 dB(A) for a stimuli length of 24 s. Fifty-six subjects rated their short-term annoyance reactions on the ICBEN 11-point numerical scale. Associations between design variables (source type, procedure, and LAE) and short-term annoyance were explored by means of a linear mixed-effect model. LAE was found to be the major predictor. For the major range of LAE, no significant difference was found between annoyance to noise from the two aircraft types. Observed level differences at equal annoyance ratings were below 1 dB. Furthermore, helicopter landings were found slightly more annoying than helicopter takeoffs. [ABSTRACT FROM AUTHOR]

Acoustic-triggered conditional sampling analysis can extract the broadband-noise-related intermittent fluctuations from complicated schlieren visualization movies around the source region, which is difficult when using conventional methods. In this study, an analysis of the Mach wave radiation from a supersonic jet was performed. The extracted results properly captured the known features of the Mach waves and their sources (i.e., wavepacket at the jet boundary) and clearly showed the correlation between these near-field fluctuations and the far-field intermittent acoustic events. This analysis can potentially be applied to other broadband, intermittent turbulent noise and will provide a better understanding of their generation mechanisms. [ABSTRACT FROM AUTHOR]

Research shows that the sight of trees and the sound of moving water improve the soundscape quality of outdoor spaces exposed to road traffic noise. Effects are attributed to non-energetic masking, visual attentional distortion, and congruence between sight and hearing. However, there is no literature on such effects for aircraft noise. Aircraft noise varies from other traffic sources, i.e., in terms temporal variability, duration, and spectral composition, complicating the application of findings without further research. In a virtual reality experiment reported in this article, participants were asked to rate scenarios with different sound levels of flyovers, urban typologies, vegetation, and/ or water features. The results showed a significant improvement of the soundscape quality when (1) vegetation and (2) moving water were present, and especially when (3) vegetation and moving water were presented simultaneously, especially for residential areas in terms of the relative change. Moving water also reduced the saliency of aircraft flyovers significantly, changing the constellation of fore- and background sounds. Moving water raised the perceived audibility of the most dominant sound source too, which could be attributed to non-energetic masking effects. The findings of this study indicate that soundscape strategies can complement noise abatement in areas prone to aircraft noise. [ABSTRACT FROM AUTHOR]

Broadband shock-associated noise (BBSAN) is a prominent noise component from nonideally expanded jets in the forward and sideline directions. BBSAN from laboratory-scale jets has been studied extensively, and spatial trends in BBSAN spectral peak characteristics—frequency, level, and width—have been established. These laboratory-scale trends are compared to those for BBSAN from a tied-down F-35B operated at four engine conditions. While the peak frequency varies as expected, both spatially and across engine condition, the peak level and width do not, pointing to the need for additional research into BBSAN for high-performance military aircraft. [ABSTRACT FROM AUTHOR]

In order to investigate the effect of the quiet-time interval between aircraft noise events on the overall negative impression of aircraft noise, psychological experiments were conducted in which the quiet-time interval was varied and the number of events and duration of each stimulus were taken into account. For equal A-weighted equivalent continuous sound pressure level (LAeq) among the stimuli, it was found that overall noisiness decreased as the quiet-time interval ratio of the stimulus was increased. It was also found that the correlation between overall noisiness and LAeq was improved by adjusting for the quiet-time interval ratio or the number of events included in the stimuli, especially when participants paid attention to changes in the instantaneous noise level. This study reveals that LAeq is a good basis for evaluating the negative impressions of aircraft noise, but that correcting for the quiet-time interval and/or number of flights improves the correlation between LAeq and the negative impression in such aircraft noise situations. [ABSTRACT FROM AUTHOR]

A single-point, frequency-domain nonlinearity indicator is calculated and analyzed for noise from a model-scale jet at Mach 0.85, Mach 1.8, and Mach 2.0. The nonlinearity indicator, νN, has been previously derived from an ensemble-averaged, frequency-domain version of the generalized Burgers equation (GBE) from Reichman, Gee, Neilsen, and Miller [J. Acoust. Soc. Am. 139, 2505–2513 (2016)]. The indicator gives the spatial rate of change due to nonlinear processes in sound pressure level (SPL) spectrum, and two other indicators from the GBE—νS and να—give the same quantity due to geometric spreading and absorption, respectively. Trends with frequency, angle, distance, and jet condition—supported both by spectral analysis and by calculation of the GBE-derived indicators—reveal a concentration of nonlinear effects along radials close to the plume with large overall SPLs. The calculated indicators for nonlinearity and absorption effects far from the source combine to give the same decay predicted by nonlinear theory for monofrequency sources. Trends in the νN indicator are compared with trends observed for other indicators such as pressure-derivative skewness and bicoherence, revealing both the qualitative and quantitative advantages of the νN indicator. [ABSTRACT FROM AUTHOR]

This paper is concerned with the influence of camber on the noise of a wall-mounted finite airfoil with natural boundary layer transition. Tonal noise measurements taken in an aeroacoustic wind tunnel are presented for airfoils with aspect ratio of 2, NACAxx12 profile and camber between 0 and 6% at 40% chord. The results show camber is an important parameter that determines the operating conditions for which acoustic tone generation occurs and the number and intensity of the tones produced. Airfoils with 0%–2% camber have an acoustic signature that is dominated by a high amplitude primary tone, whereas the spectra of airfoils with higher camber of 4%–6% feature a more pronounced side tone structure. Tonal noise production does not collapse with lift coefficient, demonstrating that the local flow conditions influence the noise source. Tonal noise production is explained in terms of changes to mean flow topology, namely the location of flow separation, which is linked to tonal noise generation. Scaling of airfoil tonal noise is found to vary with angle of attack and pressure gradient. Empirical scaling laws for the primary tone frequency dependence on velocity are also derived for the cambered airfoils. [ABSTRACT FROM AUTHOR]

In December 2014, a new terminal building was opened at the Hanoi Noi Bai International Airport (HNBIA) with two runways, causing a 20%–30% increase in the number of flights. Three socio-acoustic surveys were conducted in August–September 2014, February–March 2015, and August–September 2015, to contribute not only to the environmental impact assessments and aircraft noise policies in Vietnam but also to more global intervention studies. Because of the change of runway use, in addition to the increased number of flights, noise exposure at each site changed considerably among the surveys. Changes in the noise exposure from the first to the second or third survey (ΔLden and ΔLnight) were used as a measure of exposure change. Multiple logistic regression analysis showed that ΔLden has a significant positive effect on annoyance regardless of ΔLden ranges, but the effect of ΔLnight on insomnia was significant only for ΔLnight > 0. Annoyance increase in the overall ΔLden range may be caused by the respondents' recognition of increase in emission in addition to practical increase in exposure. More severe attitudes to airplanes around HNBIA might increase annoyance even if noise exposure decreases. Thus, the change effect clearly occurs in annoyance but partially in insomnia. [ABSTRACT FROM AUTHOR]

Reducing aircraft noise is a major issue to be dealt with by the aerospace industry. In addition to lowering noise emissions from the engine and airframe, also the shielding of engine noise by the aircraft is considered as a promising means for reducing the perceived noise on the ground. In literature, noise shielding predictions indicate significant reductions in received noise levels for blended wing body configurations, but also for conventional aircraft with the engines placed above the wings. Little work has been done in assessing these potential shielding effects for full aircraft under real operational conditions. Therefore, in this work, noise shielding for current aircraft is investigated using both measurements and model predictions. The predictions are based on the Kirchhoff integral theory and the Modified Theory of Physical Optics. For the comparison between the predictions and measurements, Twenty Fokker 70 flyovers are considered. The data analysis approach for the extraction of shielding levels for aircraft under these operational conditions is presented. Directly under the flight path, the simulations predict an engine noise shielding of 6 dB overall sound pressure level. This is confirmed by some of the flyover data. On average, the measurements show somewhat lower shielding levels. [ABSTRACT FROM AUTHOR]

A spherical microphone array has proved effective in reconstructing an enclosed sound field by a superposition of spherical wave functions in Fourier domain. It allows successful reconstructions surrounding the array, but the accuracy will be degraded at a distance. In order to extend the effective reconstruction to the entire cavity, a plane-wave basis in space domain is used owing to its non-decaying propagating characteristic and compared with the conventional spherical wave function method in a low frequency sound field within a cylindrical cavity. The sensitivity to measurement noise, the effects of the numbers of plane waves, and measurement positions are discussed. Simulations show that under the same measurement conditions, the plane wave function method is superior in terms of reconstruction accuracy and data processing efficiency, that is, the entire sound field imaging can be achieved by only one time calculation instead of translations of local sets of coefficients with respect to every measurement position into a global one. An experiment was conducted inside an aircraft cabin mock-up for validation. Additionally, this method provides an alternative possibility to recover the coefficients of high order spherical wave functions in a global coordinate system without coordinate translations with respect to local origins. [ABSTRACT FROM AUTHOR]

Aircraft noise is consistently rated as more annoying than noise from other sources with similar intensity. In three experiments, it was investigated whether this penalty is due to the source identity of the noise. In the first experiment, four samples were played to participants engaged in a working memory task: road traffic noise, an Airbus 320 flyover, and unidentifiable, transformed versions of these samples containing the same spectral content and envelope. Original, identifiable samples were rated as more annoying than the transformed samples. A second experiment tested whether these results were due to the absence of tonal components in the transformed samples. This was partly the case: an additional sample, created from the A320 flyover by filtering out major tonal components, was rated as less annoying than the original A320 sample, but as more annoying than the transformed sample. In a third experiment, participants either received full disclosure of the generation of the samples or no information to identify the transformed samples. The transformed sample was rated as most annoying when the A320 identity was disclosed, but as least annoying when it was not. Therefore, it was concluded that annoyance is influenced by both identifiability and the presence of tonal components. [ABSTRACT FROM AUTHOR]

A distributed source model to predict fan tone noise levels of an installed turbofan aero-engine is extended to include the refraction effects caused by the fuselage boundary layer. The model is a simple representation of an installed turbofan, where fan tones are represented in terms of spinning modes radiated from a semi-infinite circular duct, and the aircraft's fuselage is represented by an infinitely long, rigid cylinder. The distributed source is a disk, formed by integrating infinitesimal volume sources located on the intake duct termination. The cylinder is located adjacent to the disk. There is uniform axial flow, aligned with the axis of the cylinder, everywhere except close to the cylinder where there is a constant thickness boundary layer. The aim is to predict the near-field acoustic pressure, and in particular, to predict the pressure on the cylindrical fuselage which is relevant to assess cabin noise. Thus no far-field approximations are included in the modelling. The effect of the boundary layer is quantified by calculating the area-averaged mean square pressure over the cylinder's surface with and without the boundary layer included in the prediction model. The sound propagation through the boundary layer is calculated by solving the Pridmore-Brown equation. Results from the theoretical method show that the boundary layer has a significant effect on the predicted sound pressure levels on the cylindrical fuselage, owing to sound radiation of fan tones from an installed turbofan aero-engine. [ABSTRACT FROM AUTHOR]

This paper introduces a simplified model [Rapid Aviation Noise Evaluator (RANE)] for the calculation of aviation noise within the context of multi-disciplinary strategic environmental assessment where input data are both limited and constrained by compatibility requirements against other disciplines. RANE relies upon the concept of noise cylinders around defined flight-tracks with the Noise Radius determined from publicly available Noise-Power-Distance curves rather than the computationally intensive multiple point-to-point grid calculation with subsequent ISO-contour interpolation methods adopted in the FAA's Integrated Noise Model (INM) and similar models. Preliminary results indicate that for simple single runway scenarios, changes in airport noise contour areas can be estimated with minimal uncertainty compared against grid-point calculation methods such as INM. In situations where such outputs are all that is required for preliminary strategic environmental assessment, there are considerable benefits in reduced input data and computation requirements. Further development of the noise-cylinder-based model (such as the incorporation of lateral attenuation, engine-installation-effects or horizontal track dispersion via the assumption of more complex noise surfaces formed around the flight-track) will allow for more complex assessment to be carried out. RANE is intended to be incorporated into technology evaluators for the noise impact assessment of novel aircraft concepts. [ABSTRACT FROM AUTHOR]

Social surveys have been the conventional means of evaluating the annoyance caused by transportation noise. Sampling and interviewing by telephone, mail, or in person are often costly and time consuming, however. Data collection by web-based survey methods are less costly and may be completed more quickly, and hence, could be conducted in countries with fewer resources. Such methods, however, raise issues about the generalizability and comparability of findings. These issues were investigated in a study of the annoyance of aircraft noise exposure around Brazil's Guarulhos Airport. The findings of 547 interviews obtained with the aid of Facebook advertisements and web-based forms were analysed with respect to estimated aircraft noise exposure levels at respondents' residences. The results were analysed to assess whether and how web-based surveys might yield generalizable noise dose-response relationships. [ABSTRACT FROM AUTHOR]

The noise of a canonical main-element/flap high-lift device (HLD) is computed directly using compressible wall-resolved Large Eddy Simulation. An experimental database for the chosen configuration allows us to successfully validate the chosen numerical approach. Both the noise sources and the far-field acoustic pressure are shown to be well predicted. Although the two elements trailing-edge noise can be observed in the near field, the flap remains as the dominant source in the far-field. The simplicity of the studied configuration enables the comparison of the validated numerical results with a recently developed analytical model that takes into account the diffraction of the flap noise by the main-element. A two-dimensional (2D) (with and without Kutta condition) and a three-dimensional (without Kutta correction) analytical formulations are compared with the numerical results. All formulations compare favorably with the numerical reference in terms of noise levels and directivities. However, the 2D formulation with a Kutta correction provides the best quantitative agreement as expected from the narrow span of the numerical domain. The recently developed analytical model is therefore a good predictive tool for HLD, showing that it can properly account for the diffraction effect of the main element on the flap main noise source. [ABSTRACT FROM AUTHOR]

To evaluate the relationship between aircraft noise exposure and the quality of national park visitor experience, more than 4600 visitor surveys were collected at seven backcountry sites in four U.S. national parks simultaneously with calibrated sound level measurements. Multilevel logistic regression was used to estimate parameters describing the relationship among visitor responses, aircraft noise dose metrics, and mediator variables. For the regression models, survey responses were converted to three dichotomous variables, representing visitors who did or did not experience slightly or more, moderately or more, or very or more annoyance or interference with natural quiet from aircraft noise. Models with the most predictive power included noise dose metrics of sound exposure level, percent time aircraft were audible, and percentage energy due to helicopters and fixed-wing propeller aircraft. These models also included mediator variables: visitor ratings of the "importance of calmness, peace and tranquility," visitor group composition (adults or both adults and children), first visit to the site, previously taken an air tour, and participation in bird-watching or interpretive talks. The results complement and extend previous research conducted in frontcountry areas and will inform evaluations of air tour noise effects on visitors to national parks and remote wilderness sites. [ABSTRACT FROM AUTHOR]

This study explored the effect on memory and psychomotor performance of wideband noise (simulated in-cabin aircraft noise) at 75 dBA, which is similar to that experienced during the cruise phase of a commercial flight. The results from the tests were compared to the effects of a widely known and common metric on the same skills, namely, blood alcohol concentration (BAC). All 32 participants, half non-native English speakers, completed three different tests (recognition memory, working memory, and reaction time) presented in counterbalanced order, either in the presence of noise, with or without noise attenuation headphones, and without noise but with a BAC of 0.05 or 0.10. Simulated aircraft noise was found to affect recognition memory but not working memory or reaction time. These effects were more pronounced for non-native speakers and reflected performance similar to that for BAC of 0.05 or 0.10. [ABSTRACT FROM AUTHOR]

To expand national air transportation capabilities, NASA's Commercial Supersonic Technology Project is working to make supersonic flight practical for commercial passengers. As an aid in designing and certifying quiet supersonic aircraft, a noise metric is sought that will correspond to indoor annoyance caused by sonic booms, including the effects of indoor rattle sounds. This study examines how well several common aircraft noise metrics predict indoor annoyance based on the indoor and outdoor sound fields. The results suggest notional community annoyance models that include the effects of indoor rattle sounds. [ABSTRACT FROM AUTHOR]

Ground reflections cause problems when estimating the direction of arrival of aircraft noise. In traditional methods, based on the time differences between the microphones of a compact array, they may cause a significant loss of accuracy in the vertical direction. This study evaluates the use of first-order directional microphones, instead of omnidirectional, with the aim of reducing the amplitude of the reflected sound. Such a modification allows the problem to be treated as in free field conditions. Although further tests are needed for a complete evaluation of the method, the experimental results presented here show that under the particular conditions tested the vertical angle error is reduced ~10° for both jet and propeller aircraft by selecting an appropriate directivity pattern. It is also shown that the final level of error depends on the vertical angle of arrival of the sound, and that the estimates of the horizontal angle of arrival are not influenced by the directivity pattern of the microphones nor by the reflective properties of the ground. [ABSTRACT FROM AUTHOR]

Regulatory agencies often define strict, decibel-denominated thresholds of significance of noise impacts to protect some fraction of the residential population from exposure to highly annoying noise. Definitions of the "significance" of aircraft noise impacts and recommendations of land use "compatibility," however, typically lack detailed, systematic rationales. Instead, the definitions are justified by reference to decades-old policies that were adopted without benefit of modern understandings of noise-induced annoyance, by appeals to authority, and by generic citations of non-peer reviewed documents. Although regulatory policy decisions may properly take into consideration political and economic consequences, aspects of them are amenable to logical formalization. In particular, advances in understanding of community reaction to transportation noise now permit a systematic rationale for aircraft noise regulation. The current analyses show how regulatory policy positions can be derived from two parameters: (1) the minimal percentage of the population of a nominally average community to be protected from exposure to highly annoying noise; and (2) the percentage of all communities to which this degree of protection is intended to apply. Together with a reliable dosage-response relationship, these two parameters permit quantitatively justifiable definitions of significant noise impact. [ABSTRACT FROM AUTHOR]

Studies of effects on speech intelligibility from aircraft noise in outdoor places are currently lacking. To explore these effects, first-order ambisonic recordings of aircraft noise were reproduced outdoors in a pergola. The average background level was 47 dB LAeq. Lists of phonetically balanced words (LASmax,word=54 dB) were reproduced simultaneously with aircraft passage noise (LASmax,noise=72-84 dB). Twenty individually tested listeners wrote down each presented word while seated in the pergola. The main results were (i) aircraft noise negatively affects speech intelligibility at sound pressure levels that exceed those of the speech sound (signal-to-noise ratio, S/N<0), and (ii) the simple A-weighted S/N ratio was nearly as good an indicator of speech intelligibility as were two more advanced models, the Speech Intelligibility Index and Glasberg and Moore's [J. Audio Eng. Soc. 53, 906-918 (2005)] partial loudness model. This suggests that any of these indicators is applicable for predicting effects of aircraft noise on speech intelligibility outdoors. [ABSTRACT FROM AUTHOR]

Many older studies of community response to aircraft noise in fact used the same logic of questionnaire organization and wording, absolute judgment response scales, and order of questioning as more recent studies. Only five (of 65) surveys report a value of DNL of 45 dB or lower at the 10% high annoyance point.[2] Given that more than 90% of published studies indicate supposedly "unsafe" aircraft noise exposure conditions, one could reasonably expect reported risk ratios to document adverse health outcomes substantially higher than the marginal ones typically observed. Response to "Comment on 'Recent World Health Organization regulatory recommendations are not supported by existing evidence' " [J. Acoust. [Extracted from the article]

The first problem of the article is a lack of relevant information about study objectives, data sources, and data extraction methods, which would be needed to retrace the exact steps taken in the analyses and eventually understand and agree to its conclusions. The objective of Gjestland's study is not really made explicit in the introduction, and the article does not state a specific research question or hypothesis against which the subsequent (statistical) analysis could be judged adequate or not. It does not become clear whether the article is a critique of the methodology (and study selection) applied in the work by [4] for the WHO or if it addresses the question of whether aircraft noise annoyance has increased over the last decades or not. [Extracted from the article]

Assessment of aircraft noise-induced sleep disturbance is problematic for several reasons. Current assessment methods are based on sparse evidence and limited understandings; predictions of awakening prevalence rates based on indoor absolute sound exposure levels (SELs) fail to account for appreciable amounts of variance in dosage-response relationships and are not freely generalizable from airport to airport; and predicted awakening rates do not differ significantly from zero over a wide range of SELs. Even in conjunction with additional predictors, such as time of night and assumed individual differences in 'sensitivity to awakening,' nominally SEL-based predictions of awakening rates remain of limited utility and are easily misapplied and misinterpreted. Probabilities of awakening are more closely related to SELs scaled in units of standard deviates of local distributions of aircraft SELs, than to absolute sound levels. Self-selection of residential populations for tolerance of nighttime noise and habituation to airport noise environments offer more parsimonious and useful explanations for differences in awakening rates at disparate airports than assumed individual differences in sensitivity to awakening. [ABSTRACT FROM AUTHOR]

Noise measured in the vicinity of an F-22A Raptor has been compared to similarity spectra found previously to represent mixing noise from large-scale and fine-scale turbulent structures in laboratory-scale jet plumes. Comparisons have been made for three engine conditions using ground-based sideline microphones, which covered a large angular aperture. Even though the nozzle geometry is complex and the jet is nonideally expanded, the similarity spectra do agree with large portions of the measured spectra. Toward the sideline, the fine-scale similarity spectrum is used, while the large-scale similarity spectrum provides a good fit to the area of maximum radiation. Combinations of the two similarity spectra are shown to match the data in between those regions. Surprisingly, a combination of the two is also shown to match the data at the farthest aft angle. However, at high frequencies the degree of congruity between the similarity and the measured spectra changes with engine condition and angle. At the higher engine conditions, there is a systematically shallower measured high-frequency slope, with the largest discrepancy occurring in the regions of maximum radiation. [ABSTRACT FROM AUTHOR]