bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of active and passive hearing protective devices on sound source localization, tone detection, and speech recognition
Authors: Brown Andrew D. , Beemer Brianne T. , Greene Nathaniel T. , Tollin Daniel J.
Published: May 2015

Hearing protective devices (HPDs) such as earplugs and earmuffs offer to mitigate noise exposure and thus noise-induced hearing loss among persons frequently exposed to intense sound, e.g., military personnel or industrial workers. However, distortions of spatial acoustic information and attenuation of low-intensity sounds caused by many existing HPDs can make their use untenable in high-risk environments where auditory situational awareness is imperative. Here, we assessed (1) sound source localization accuracy using a head-turning paradigm, (2) tone detection thresholds using a two-alternative forced-choice task, and (3) speech-in-noise recognition using a modified version of the QuickSIN test in 10 young normal-hearing males wearing four different HPDs (two active, two passive), including two new and previously untested devices. Relative to unoccluded (control) performance, all tested HPDs significantly degraded performance across tasks, although one active HPD slightly improved high-frequency tone detection thresholds, and did not degrade speech recognition. Behavioral data were examined with respect to binaural acoustic information (directional transfer functions) measured in a binaural manikin with and without tested HPDs. Data reinforce previous reports that HPDs significantly compromise auditory perceptual facilities, particularly sound localization due to distortions of high-frequency pinna cues.
Multiple sound source localization when sounds are stationary or rotating
Authors: Zhong Xuan , Yost William
Published: May 2015

In the field of spatial hearing, it is known that the sound source localization error increases when distractors are present. This study first determined the maximum number of sound sources that can be perceived. In one experiment, listeners determined how many sources (loudspeakers) presented sounds and these loudspeaker locations. In another experiment, listeners were asked to locate a new sound source which was added to an existing set of fixed sources. Listeners determined up to about four sources producing simultaneous unrelated speech sounds in both experiments. A second part of the research examined the effect of rotating the sound sources on the listener’s perception. If multiple unrelated sounds such as speech rotated, listeners could much more easily determine sound rotation than if the sounds were related to each other. If the sounds were related (e.g., all sounds were harmonics of a fundamental) but were still presented from a number of different loudspeakers, listeners could hardly process the individual sounds even when sounds rotated among the loudspeakers. Thus, the ability to locate multiple sound sources depends on the total number and motion of sources and the type of sound. [Research supported by an AFOSR grant.]
Measuring the auditory phase response based on interaural time differences
Authors: Tabuchi Hisaaki , Laback Bernhard , Majdak Piotr , Necciari Thibaud , Zenke Katherina
Published: May 2015

Harmonic complexes are often used as maskers for measuring the cochlear phase response. The phase curvature can affect the masking in order of up to 20 dB, an effect known as the masker-phase effect. There is evidence that signals yielding peaky internal masker representations after passing the cochlear filter produce minimum masking, with the fast-acting cochlear compression as the main contributor to that effect. Thus, in hearing-impaired listeners showing reduced or absent compression, the estimation of phase response using the masking method may be difficult. Here, an alternative method is proposed, which is based on the effect of signal peakedness on the sensitivity to interaural time differences (ITD) in the signal envelope. With the two methods, ITD and masking thresholds were measured, respectively, in seven normal-hearing listeners. The stimuli were 300-ms Schroeder-phase harmonic complexes, ranging from 3400 to 4600 Hz with a 100-Hz fundamental frequency, with the signal phase curvature varied between −1 and 1. The lowest ITD thresholds were observed for phase curvatures that produced minimum masking. This suggests that the ITD method is a promising candidate for estimating the cochlear phase response in hearing-impaired listeners.
Effect of spectrally-remote maskers on sentence recognition by adults and children
Authors: Youngdahl Carla L. , Yoho Sarah E. , Frush Holt Rachael , Apoux Frederic , Healy Eric W.
Published: May 2015

Adults display improved detection of a signal in noise when the spectral frequency of that signal is known, relative to when it is unknown. In contrast, infants do not display this improvement, suggesting that they monitor all frequencies equally, even when it is not advantageous to do so. To assess the impact of this “spectral attention” development during speech recognition, sentences in noise were lowpass filtered at 1500 Hz and presented along with spectrally remote low-noise noise maskers that produced no spectral overlap of peripheral excitation. As anticipated, sentence recognition by adults was not affected by the presence of remote maskers, irrespective of their bandwidth and spectral location. This result was also observed in a group of 7-year-old children. However, the youngest children tested (5-year-olds) displayed poorer sentence recognition in the presence of the remote maskers, suggesting that they were unable to focus attention on the spectral region of speech. The current results suggest that an important step occurs in the development of auditory spectral attention around age 6. These results may also help explain why children typically require more favorable signal-to-noise ratios than adults to achieve similar levels of speech performance in noise. [Work supported by NIH.]
Adult listener’s detection thresholds for vowels and two-syllable words in different two-talker maskers
Authors: Oster Monika-Maria , Werner Lynne A.
Published: May 2015

There is an increased interest in using natural speech targets and speech maskers to assess infants’ auditory skill development. While providing ecological validity, natural speech is an inherently uncontrolled signal. Discrepancies between existing studies may be the result of differences in the maskers and/or target stimuli used. This study explores adult listener’s detection thresholds for vowels and two-syllable words in three different two-talker maskers to assess the impact of (1) masker characteristics and (2) differences in target signals. Each two-talker masker was created by recording two female speakers reading different passages in monotone, in adult-directed style, or infant-directed style. Silences longer than 300 ms were deleted, and the passages’ root-mean-square amplitudes balanced before combining them. The target stimuli consisted of the vowels /a/, /o/, /e/ and the words “baby” and “ice-cream.” They were spoken by different female talkers in both adult-directed and infant-directed styles. An adaptive two-interval forced choice method was used to estimate threshold. Preliminary results suggest that there are small differences in detection thresholds between the different two-talker maskers. Larger differences are found between the thresholds of different target signals, indicating that discrepancies between existing studies may be due to differences in target stimuli used.
Source localization and signal extraction using spherical microphone arrays
Authors: Bai Mingsian R. , Yao Yueh Hua
Published: May 2015

Source localization and extraction using spherical microphone arrays is presented in this paper. Both freefield and solid spherical arrays are examined. To minimize the basis mismatch problem in signal extraction, source localization is executed first using two beamforming methods, delay and sum (DAS) and minimum variance distortionless response (MVDR). The beamformers are formulated in both the spatial domain and the modal domain. After source localization, Tikhonov regularization (TIKR) and compressive sensing (CS) are used to extract the source amplitude signals. Simulations and experiments are conducted for spherical arrays of radius 5 cm with 32 microphones mounted on the vertices and faces of an icosahedron. The results demonstrate better localization performance of the spatial beamformer that the modal beamformer. In addition, the source speech signals are extracted by using the proposed arrays with superior quality.
Active and passive monitoring of valve bodies utilizing spray-on transducer technology
Authors: Ledford Kenneth R. , Sinding Kyle , Tittmann Bernhard
Published: May 2015

Structural health monitoring (SHM) and non-destructive evaluation (NDE) can be performed both actively and passively. Active monitoring is useful for thickness measurement and crack interrogation. Passive monitoring can indicate integrity of the valve and if it is open or closed. Traditional SHM methods for valve bodies require a bonding medium that can deteriorate. A sol-gel spray-on technology eliminates the need for a coupling medium since the transducer is chemically bonded to the valve body. These spray-on transducers can be tailored to specific applications in order to maximize response or operating temperature. This technology allows for efficient on-line monitoring of valve bodies for thickness and valve integrity. The current objective is to develop a spray-on transducer and corresponding method for both active and passive SHM of valve bodies. The objective relating specifically to passive monitoring relates to indicating the condition of the valve and determining what position it is in. The active monitoring goals are to measure the thickness of the valve in critical regions, determine the presence of corrosion, and observe the roughness of the interior surface. This paper provides preliminary results on the use of spray-on transducers for on-line SHM of valve bodies for both active and passive applications.
Measurement of the moisture content of a waste paper bale based on the impact resonance test
Authors: Song Minho , Kim Donghyun , Ohm Won-Suk , Um Baek-Yong
Published: May 2015

The quality of a waste paper bale depends heavily on its moisture content. The higher the moisture content, the lower the quality as a recycled resource. Therefore, accurate measurement of the moisture content of a waste paper bale is a pressing concern in the paper recycling industry. In this paper, a theoretical model for a waste paper bale, an exotic and complex medium, is developed, in which the acoustic properties of the bale are assumed to be functions of the moisture content. The model is validated through a series of impact resonance tests, which show a strong correlation between the moisture content, resonance frequencies, and the associated quality factors.
Modeling the balance between bottom-up and top-down processing in speech intelligibility tests
Authors: Uslar Verena N. , Brand Thomas , Kollmeier Birger
Published: May 2015

Understanding speech depends on sensory, input-driven bottom-up processing as well as on top-down processing-based, e.g., on experience—which is typically associated with more effortful listening. A qualitative and quantitative analysis of the respective contribution of both processing types is important to further diagnostics of hearing impairment, rehabilitation with hearing devices, and the predictive quality of speech intelligibility models. This talk gives a short overview of studies, which measured speech intelligibility as a function of linguistic complexity to quantify the respective contribution of both processing types. Comparison of speech reception thresholds for linguistically simple and more complex sentences in varying listening situations for younger and older adults with normal hearing and with hearing-impairment indicated that experience-driven top-down processing becomes more important with increasing listening effort. All listener groups seem to use the same mechanisms to compensate for increasing sensory or cognitive load, however the threshold for employing experience-driven top-down processing seems to lower with increasing age and hearing impairment. These results led to the development of the so called “speech processing gauge” presented here which explains the shift of the balance between bottom-up and top-down processing with regards to changes in different variables, i.e., age, hearing impairment, sensory load, and cognitive effort.
Task demands and cognitive abilities impact listening effort for older adult hearing aid users
Authors: Kuchinsky Stefanie E. , Ahlstrom Jayne B. , Franko-Tobin Emily , Dubno Judy R.
Published: May 2015

Understanding speech in background noise requires considerable effort for older adults with hearing loss, even when wearing well-fit hearing aids, but little is known about how effort varies with changes in speech recognition task demands in this population. Following research showing that effort can be indexed by changes in the autonomic pupil dilation response, the current study recorded pupillometry as older adults wearing hearing aids completed the Words-In-Noise test (e.g., Wilson et al., 2007). Using a single loudspeaker at 0 degrees azimuth, participants listened to and repeated monosyllabic words in multi-talker babble at seven signal-to-noise ratios (0 to + 24 dB SNR). A nonlinear relationship between word recognition score and pupil dilation was observed, with maximal effort at moderate levels of speech recognition difficulty. Individual differences in cognitive abilities (e.g., working memory, vocabulary knowledge) modulated this pattern of results. These findings highlight an important dissociation between listening effort and speech recognition task difficulty. Implications for evaluating changes in effort with speech-perception training are discussed. [Work supported, in part, by NIH/NIDCD.]
Coded excitation in space and time for the identification of geometric parameters using audio transducer arrays
Authors: Choi Jung-Woo
Published: May 2015

Impulse responses of a room can provide a lot of geometric information of acoustic systems. Loudspeaker and microphone array positions, locations of walls and scattering bodies are representative examples. To extract geometric information from the room impulse responses, the measurement time should be short enough such that the degradation of time delay estimation performance due to non-stationary environmental noises can be minimized. In this work, we attempt to enhance the SNR of the short-term measurement, by using a coded excitation technique in space and time. Both the spatially and temporally coded excitation signals are applied to a set of loudspeakers combined with microphones, and it is shown that the measurement time can be shortened with minimal loss of SNR and time delay estimation performance.
Testing spatial co-prime sampling theory
Authors: Bautista Radienxe , Buck John R
Published: May 2015

An array of sensors can be used to estimate the direction of arrival of a narrowband signal in the far field with the use of conventional beamforming. In order to avoid spatial aliasing, the distance between the sensors have to be d ≤ λ/2 apart. This is analogous to the Nyquist theorem for sampling in time with fs= 2fo. Co-Prime arrays are non-uniform arrays that can predict what a uniform array with an aperture of L = M×N total sensors can using fewer sensors; they have a total number of sensors L = M + N—1 while maintaining an aperture of M×N sensors in a full uniform line array with λ/2 spacing between elements. Each subarray is uniform linear, equally spaced by Nλ/2 or Mλ/2 and then combined to create a non-uniform linear array. The result with the different inter-element spacing between the subarrays is grating lobes in different locations with the exception of the true DOA. Conventional beamforming is done with both subarrays and the outputs are then multiplied together to yield a single beam pattern. The theory to this will be tested using a uniform array of 30 sensors and selecting the data from certain sensors to achieve co-prime sampling.
Sound speed structure monitoring of the Antarctic Ocean by new style float
Authors: Gotoh Shinpei , Tsuchiya Toshio , Hiyoshi Yoshihisa , Mizutani Koichi
Published: May 2015

JAMSTEC developed the new profiling float “Deep NINJA” for deep-sea type, was subjected to long-term monitoring of one year in the Antarctic Ocean off the coast of Adelie Coast from 2012. As a result, succeeded in the long-term monitoring of the sound speed profile to depth of the 4000 m in the Antarctic Ocean for the first time in the world, and was able to capture a seasonal change in the surface area in the freezing season and the thawing season. In addition, calculating a sound speed from these data, simulations were performed assuming the low frequency sonar. The result was obtained, the ingredient which propagates while repeating a reflection in the extremely small layer of the sea surface neighborhood, and the ingredient that propagates while being reflected in near the water depth 100m which changes of sound speed gradient. From this, propagation loss was small in winter than summer, and was shown a possibility that a sound wave would propagate to a more distant place. This may affect the long-distance sound wave propagation of the echo locations of the passive sonar and marine mammals.
Second-order statistics of the instantaneous mutual information in time-varying underwater acoustic particle velocity channels
Authors: Chen Chen , Wang Shuangquan , Abdi Ali
Published: May 2015

Instantaneous mutual information (IMI) is the amount of information that a time-varying channel can convey for the given time instant. In this paper, second-order statistics of IMI are studied in time-varying underwater acoustic particle velocity channels. First, the autocorrelation function, correlation coefficient, level crossing rate, and average outage duration of IMI are provided in a time-varying fading channel. Exact expressions are given in terms of the summation of special functions, which facilitate numerical calculations. Then, accurate approximations for the autocorrelation function and correlation coefficient are presented for low and high signal-to-noise ratios. Moreover, analytical and numerical results are provided for the correlation and level-crossing characteristics of IMI in underwater particle velocity channels. The results shed light on the dynamic behavior of mutual information in underwater acoustic particle velocity channels. [Work supported in part by the National Science Foundation (NSF), Grant CCF-0830190.]
Comparative sensitivity of pressure gradient receivers of force and inertial types to sound pressure in plane wave
Authors: Korenbaum Vladimir , Gorovoy Sergei , Tagiltcev Alexandr , Kostiv Anatoly
Published: May 2015

Among known constructing schemes of pressure gradient receivers (PGR)—a difference type (including two-point version), a force type, and an inertial one—only the last two types are applicable when receiver size is much smaller than a wavelength of plane wave. Each of these two PGR types has certain advantages/disadvantages for various applications. The objective is a comparison of these PGRs, having identical external dimensions, by their sensitivity to sound pressure. In the long-wave two-dimensional approach the expression for a sensitivity to sound pressure is derived for a force type PGR, in which plate bending piezoelectric transducer is installed in a passage of the cylindrical housing. Also, the expression is developed for the sensitivity to sound pressure of an inertial type PGR with a one-component accelerometer embedded into its cylindrical housing. We derived the expression to estimate required one-side pressure sensitivity of the bending piezoelectric transducer of the force type PGR to equalize the sensitivities of PGRs of both types to sound pressure when the vibration sensitivity of the accelerometer is known. Possibilities of increasing sensitivity of the force type PGR are considered. [The study was supported by the grant 15-IV-1-001 of Far Eastern Branch of Russian Academy of Sciences.]
Possibility of acoustic noise interferometry applications for passive remote sensing in shallow water
Authors: Sergeev Sergei , Shurup Andrey , Scherbina Alisa , Mukhanov Pavel
Published: May 2015

The cross-coherence function of the ambient noise field received during the quite long accumulation time by two hydrophones in the shallow water can exhibit two peaks. These peaks correspond to the travel times of signals between these two hydrophones. If the features of the shallow water are changed than the positions of these peaks are shifted. As result one can get information to reconstruct the physical properties and variability of the underwater environment using such peaks’ shifts. In this work, the possibility of the passive remote sensing in shallow water features is considered based on the time-frequency analysis of the ambient noise cross-coherence function. The key point which define the possibilities of this method are the accumulation times required to estimate the peaks of the noise cross-coherence function with the acceptable signal-to-noise ratio. It is shown that the desired accumulation times can be considerably reduced by the appropriate choice of the frequency bands where the noise fields are formed by the small number of the incoherent hydroacoustic modes.
Auditory and non-auditory effects of noise on health: An ICBEN perspective
Authors: Basner Mathias
Published: May 2015

Noise is pervasive in everyday life and induces both auditory and non-auditory health effects. Noise-induced hearing loss remains the most common occupational disease in the United States, but is also increasingly caused by social noise exposure (e.g., through music players). Simultaneously, evidence on the public health impact of non-auditory effects of environmental noise exposure is growing. According to the World Health Organization (WHO), ca. 1.6 Million healthy life years (DALYs) are lost annually in the western member states of the European Union due to exposure to environmental noise. The majority (>90%) of these effects can be attributed to noise-induced sleep disturbance and community annoyance, but noise may also interfere with communication and lead to cognitive impairment of children. Epidemiological studies increasingly support an association of long-term noise exposure with the incidence of hypertension and cardiovascular disease. Up-to-date exposure-response relationships are needed for health impact assessments, to reassess the validity of current noise policy and to better mitigate the negative health consequences of noise. The International Commission on Biological Effects of Noise (ICBEN) is a non-profit organization constituted 1978 that promotes all aspects of noise effects research and its application through International Noise Teams and an International Congress every three years.
Karl Kryter and psychoacoustics at Bolt Beranek and Newman
Authors: Beranek Leo
Published: May 2015

Karl Kryter joined Bolt Beranek and Newman from Harvard in 1957. He was named the head of the Department of Psychoacoustics where he worked with his close friend, J. C. R. Licklider. His first work was with speech intelligibility in noise. He was the psychoacoustician on the team of three with Laymon Miller and Leo Beranekin a multi-year project for the Port York Authority that led to the reduction of noise created by the first jet commercial aircraft, the Boeing 707, by 15 dB. He was responsible for developing a means for measuring the perception by people of the loudness of noise—particularly aircraft noise. Named the perceived noise decibel PNDB, it remains today the accepted method for measuring the effect of noise on people living around airports. After that he did sleep research until he departed in 1966 for the Stanford Research Institute.
Effects of hospital noise on speech intelligibility
Authors: Gallun Frederick J.
Published: May 2015

The most straightforward way to consider the effects of noise on the ability to understand speech is in terms of overlap of energy at the level of the cochlea. This approach, sometimes called “energetic masking” has been well studied and is quantified in a number of international standards such as the Speech Intelligibility Index (ANSI, 2004). Recently, however, another aspect of noise has captured the interest of those studying speech intelligibility. Known as “informational masking,” this refers to the ability of noise to interfere with intelligibility even when energetic overlap is low. A study describing this phenomenon with respect to hospital noise will be described and it will be demonstrated that the impact of human voices on speech intelligibility provides a difficult problem for those trying to predict and quantify the effects of noise based only on the statistics of the acoustical signal.
Zeitgeist from Kryter’s work at the PsychoAcoustics Laboratory at Harvard to the present
Authors: Florentine Mary , Epstein Michael
Published: May 2015

Kryter’s writings indicate that he was keenly aware that intense sounds damage auditory systems. He was also aware that there is no one-to-one correspondence between the physical world and our perception of it. In fact, much of Kryter’s work sought to summarize that relationship in general terms as they applied to average observers. He consistently sought an inclusive theoretical framework. Kryter would have been fascinated by the recent discoveries regarding individual differences among listeners with different types of hearing losses. He would have delighted in the recent connections made between psychoacoustics and physiology, and the trend toward ecologically valid research. This presentation traces the zeitgeist from his work at the PsychoAcoustics Laboratory (PAL) at Harvard to the present, examining loudness across the entire dynamic range for listeners with normal hearing and different types of hearing losses. [This work was supported, in part, by NIH-NIDCD grants 1R03DC009071 and R01DC02241.]
Noise-induced cochlear synaptopathy: Extending effects of noise on man?
Authors: Kujawa Sharon G.
Published: May 2015

Kryter wrote that “…methods commonly used in medicine for the evaluation of impairment to hearing and the relation of this impairment to noise exposure may lead to significant underestimates of the severity of noise-induced hearing impairment and overestimations of tolerable limits for exposure to noise.” (J. Acoust. Soc. Am. 53(5), 1211–1234). Although specifics differ, recent work in our laboratory provides strong evidence supporting this assertion. In a series of investigations conducted over the last 5 years, we have shown that a primary consequence of noise exposure is acute loss of synapses between cochlear inner hair cells (IHC) and auditory nerve fibers followed by loss of the affected neurons themselves. Losses are robust, permanent, and progressive, even for temporary threshold shift-producing exposures, and aging of these ears is exaggerated, going forward. This noise-induced injury can hide behind normal thresholds, our traditional evidence of recovery; however, communication between IHCs and nerve fibers is nevertheless permanently interrupted. We hypothesize that these synaptopathic and neurodegenerative consequences of noise may contribute to speech discrimination difficulties in challenging listening environments. This talk will summarize what we know about structural and functional consequences and noise-risk implications of noise-induced cochlear synaptopathy. [Research supported by R01 DC 008577.]
The role of form in modeling auditory scene analysis
Authors: Denham Susan , Coath Martin
Published: May 2015

Separating out and correctly grouping the sounds of a communicating animal from the natural acoustic environment poses significant challenges to models of auditory scene analysis, yet animals perform this task very effectively. To date, most models have focussed on simultaneous grouping cues and the segregation of discrete sound events, although some take the longer term context into account. Inspired by the important part that form plays in the segregation and recognition of visual objects, we consider the role of form in auditory scene analysis. By form in audition we mean the dynamic spectrotemporal patterns characterizing individual sound events as well as their timing with respect to each other. We present a model capable of segregating and recognizing natural communication calls within complex acoustic environments. Incoming sounds are processed using a model of the auditory periphery and fed into a recurrent neural network that rapidly tunes itself to respond preferentially to specific events. Representations of predictable patterns of events in the sequence are created on the fly and maintained on the basis of their predictive success and conflict with other representations. Activation levels of these representations are interpreted in terms of object recognition.
Active enhancement found in responses of the cochlear nerve to detect weak echoes created by the auditory periphery in Japanese house bat, Pipistrelus abramus
Authors: Riquimaroux Hiroshi , Onodera Hiroshi , Matsuo Ikuo
Published: May 2015

Characteristics of frequency tunings related to echolocation were investigated in an FM bat, Japanese house bat (Pipistrellus abramus). A particular attention was paid on their terminal frequency of FM sweep. When search for preys in the field, they stretch duration of echolocation pulses and reduce FM sweeping range, resulting in pseudo constant frequency pulses. Distribution of best frequency in the neurons in the inferior colliculus indicated that about 50% of neurons appeared to be tuned to the pseudo constant frequency, around 40 kHz. The compound action potentials were recorded from medulla oblongata through a metal telectrode. We hypothesized that the bat has a peripheral system to enhance frequency component of 40 kHz to be detected easier than other frequency components. Active enhancement of 40 kHz frequency component by the outer hair cell and overwhelming number of cochlear nerves in charge of 40 kHz would create low threshold and high resolution sensitivity for frequency range around 40 kHz. Results of the present study show that compound action potential of the cochlear nerve (N1) generates nonlinearly enhanced amplification in frequency range of 40 kHz but linear amplification in lower frequency ranges.
Evaluation of a simple model for the acoustics of bat swarms
Authors: Liu Mingyi , Müller Rolf
Published: May 2015

Bats using their biosonar while flying in dense swarms may face significant bioacoustic challenges, in particular mutual sonar jamming. While possible solutions to the jamming problem have been investigated several times, the severity of this problem has received far less attention. To characterize the acoustics of bat swarms, a simple model of the acoustically relevant properties of a bat swarm has been evaluated. The model contains only four parameters: bat density, biosonar beamwidth, duty cycle, and a scalar measure for the smoothness in the flight trajectories. In addition, a threshold to define substantial jamming was set relative to the emission level. The simulations results show that all four model parameters can have a major impact on jamming probability. Depending on the combination of parameter values, situations with or without substantial jamming probabilities could be produced within reasonable ranges of all model parameters. Hence, the model suggests that not every bat swarm does necessarily impose grave jamming problems. Since the model parameters should be comparatively easy to estimate for actual bat swarms, the simulation results could give researchers a way to assess the acoustic environment of actual bat swarms and determine cases where a study of biosonar jamming could be worthwhile.
Noise induced threshold shifts after noise exposure: Are bats special?
Authors: Simmons Andrea , Warnecke Michaela , Hom Kelsey , Simmons James
Published: May 2015

We conducted psychophysical and neurophysiological experiments to test the hypothesis that big brown bats suffer less severe temporary threshold shifts after noise exposure than other small mammals that also hear high frequency sounds. Five big brown bats were trained in psychophysical detection experiments to obtain thresholds to FM sweeps spanning the frequency range of their echolocation calls. Bats were then exposed to 115 dB of broadband noise for one hour, and thresholds re-measured 20 min and 24 hour after exposure. For all bats, threshold elevations at 20 min post-exposure were 3 dB or less, while at 24 hour post-exposure, thresholds were similar to those obtained pre-exposure. Local field potentials were recorded in the cochlear nucleus of anesthetized big brown bats before and after noise exposure. Neural thresholds to FM sweeps and to single tone frequencies were unaffected by noise exposure. These data suggest that big brown bats are an excellent model system to study naturally occurring immunity to noise damage. [Work supported by ONR and the Capita Foundation.]
Role of lipid coating properties on nonlinear microbubble dynamics
Authors: Kooiman Klazina
Published: May 2015

Although nonlinear microbubble dynamics are exploited in many contrast-enhanced ultrasound imaging modalities, the role of lipid coating properties on nonlinear dynamics is not fully understood. Our studies show that microbubble vibrations differ between bubbles with homogeneous lipid distribution (main component DPPC, C16) and bubbles with heterogeneous lipid distribution (main component DSPC, C18). Relative to DPPC microbubbles, DSPC microbubbles were shown to elicit more second harmonic emissions, but exhibit a lower propensity to initiate subharmonic emissions. This suggests that homogeneous microstructures favor subharmonic emissions, whereas heterogeneous microstructures produce higher second harmonic emissions. Additionally, the nonlinear “compression-only” oscillation behavior is hypothesized and theoretically shown to relate to buckling of the lipid coating. High-speed fluorescence recordings revealed for the first time formation of hot spots (i.e., high local concentrations of lipids) in the coating of oscillating microbubbles during the compression phase, suggesting evidence of buckling/folding of the coating. However, hot spots were not correlated to compression-only behavior, but were related to the level of compression of the microbubbles during insonification, with a relative compression threshold of 15–20%. This suggests that compression-only behavior is not directly related to buckling of the lipid coating. This work sheds insight into the role of lipid coating properties on nonlinear microbubble behavior.
Radiation damping of an arbitrarily shaped bubble
Authors: Spratt Kyle S. , Lee Kevin M. , Wilson Preston S. , Wochner Mark S. , Hamilton Mark F.
Published: May 2015

Large encapsulated bubbles have recently been used for abating low-frequency anthropogenic underwater noise [J. Acoust. Soc. Am. 135, 1700–1708 (2014)]. The use of encapsulation allows for the possibility of bubbles that are significantly nonspherical in their equilibrium state. Strasberg [J. Acoust. Soc. Am. 25, 536–537 (1953)] investigated the resonance frequency of an ideal bubble with arbitrary shape and found that the dependence of resonance frequency on the shape of the bubble reduced to a well-known problem in electrostatics. The present work extends that analysis to include the effects of radiation damping on the oscillation of a bubble, and does so by including a loss term due to Ilinskii and Zabolotskaya [J. Acoust. Soc. Am. 92, 2837–2841 (1992)] in the volume-frame dynamical equation for the bubble. An expression is given for the amplitude of the acoustic field scattered from the bubble, and it is shown that radiation damping scales as resonance frequency cubed for arbitrarily shaped bubbles having the same volume. Comparisons are made with previous work on scattering from spherical and prolate spheroidal bubbles, and various new bubble shapes are considered. [Work supported by AdBm Technologies, the ARL:UT McKinney Fellowship in Acoustics and ONR.]
Soundscape as a resource to balance the quality of an acoustic environment
Authors: Schulte-Fortkamp Brigitte
Published: May 2015

Impacts of noise on people's quality of life, on their health, and on the quality of the living environment, including economic costs will be addressed in this paper. It follows the understanding of potential health effects related to noise by the European Environment Agency. “Adverse effects of noise occur when intended activities of the individual are disturbed. The sound level of the acoustic stimulus, its psychoacoustical sound characteristics, the time of its occurrence, its time course, its frequency spectrum, and its informational content will modify the reaction.” EEA 2010. To account for the diversity of living situations related research will focus on the cooperation of human/social sciences like. psychology, sociology, architecture, anthropology, and medicine. Soundscape will provide the needed paradigm shift in research and evaluation. The International Standard ISO/DIS 12913-1 has as its purpose the enabling of a broad international consensus on the definition of “soundscape” and its respective evaluation. It is more than urgent to understand that there is the need to provide a solid foundation for communication across disciplines and professions with an interest in achievements on better solutions for the people concerned.
Soundscapes and human restoration in green urban areas
Authors: van Kamp Irene , van Kempen Elise , Swart Wim , Kruize Hanneke
Published: May 2015

There is increasing interest in the association between landscapes, green and blue space, open countryside and human well-being, quality of life, and health. Most studies in this field do not account for the positive or negative moderating effects of the acoustic environment. This is partly due to the lack of relevant data, although basic models do refer to the role of traffic related noise and air-pollution. This paper reports on the results of a European study (Phenotype) into the health effect of access to and use of green area in four European cities. At the four study centers, people were selected from neighborhoods with varying levels of socioeconomic status and green space. By structured interview, information was gathered about availability, use, and importance of green space in the immediate environment, as well as the sound quality of favorite green areas used for physical activity, social encounters, and relaxation. Data are also available about perceived mental and physical health and medication use. This allows for analyzing the association between indicators of green and health, while accounting for perceived soundscapes. Audit data about the sound quality are also available at neighborhood level as a point of reference.
Soundlapse: Audio strategies for documenting soundscapes with timelapse photography
Authors: Carter J. Parkman
Published: May 2015

Timelapse photography—the procedure of taking photographs at regular intervals and then sequencing them together at a rate typical of film/video (e.g., 24 frames per second) to produce a radically accelerated and compressed portrayal of time passing—is widely popular across such diverse areas as scientific research, weather tracking, filmmaking, and even reality TV shows, which commonly use timelapse footage to segue between scenes and reflect the passing of time. The compelling visual effect and broad legibility of timelapse photography makes it a powerful tool for revealing flows, shifts, and patterns in the environment, which would otherwise be too subtle to perceive in real time. One of the most important challenges in documenting the salient features of a soundscape is revealing similar shifts and patterns across time in the acoustic environment. However, temporal logic would suggest it is simply not possible to sequence such brief samples of the audio environment with any meaningful result. This project explores different audio capture and editing techniques to produce viable strategies for documenting the changes in a soundscape which accompany timelapse photography of the environment under study. Examples will be demonstrated, emphasizing the significant variables for adequately representing the elusive temporal characteristics of a soundscape.
Sweeping tunable vibration absorbers for structural vibration control
Authors: Gardonio Paolo , Zilletti Michele
Published: May 2015

Tuneable vibration absorbers (TVAs) have been successfully implemented in distributed thin structures (e.g., panels shells) to control either tonal vibration, produced, for example, by unbalanced machinery, or low-frequencies broadband vibration, generated, for example, by stochastic pressure distributions due to diffuse sound fields or turbulent boundary layer fluid flows. This study is focused on the broadband control of structural vibration where often multiple TVAs are used to control the response of the natural modes that resonate in the controlled frequency band. Normally, each TVA is tuned to minimize the resonant response of a specific natural mode of the hosting structure by tuning the TVA natural frequency to the resonance frequency of the mode and setting the TVA damping ratio to properly dissipate energy. The proposed sweeping tuneable vibration absorbers (STVAs) have been conceived to operate on the multiple natural modes of the hosting structure where they are mounted by sweeping the TVA tuning frequency over the frequency band of control and simultaneously varying the TVA damping ratio to effectively dissipate energy over the desired frequency range. The operation principle of a single STVA is first discussed and demonstrated experimentally. The implementation of multiple STVAs is then examined.
Adaptive vibration control of a mechanical system with nonlinear damping excited by a tonal disturbance
Authors: Zilletti Michele , Elliott Stephen J. , Ghandchi Tehrani Maryam
Published: May 2015

In this study, an adaptive control system to reduce the tonal vibration of a mechanical system characterized by nonlinear damping is considered. Since the response of the system to a sinusoidal excitation is however mainly sinusoidal, nonlinear controllers are not required for the control of a tone in such a mechanical system. The adaptation and stability of an adaptive control algorithm, however, depends on the accuracy of the plant model. Since the tonal response of the nonlinear system changes with excitation level, conventional adaptive algorithms, with a fix linear model of the plant, can be slow to converge and may not achieve the desired performance. The use of an online observer is proposed, to estimate the describing function model of the plant, which will vary with excitation level. This allows the adaptive control algorithm to converge more quickly than using a fixed plant model, although care has to be taken to ensure that the dynamics of the observer do not interfere with the dynamics of the adaptive controller.
The prediction of infrasonic wind noise in forests
Authors: Raspet Richard , Webster Jeremy
Published: May 2015

Recent research on the measurement and prediction of the infrasonic wind noise measured in pine and mixed deciduous forests with and without leaves has led to a good understanding of the turbulence mechanisms that generate the infrasonic wind noise. This talk will review the success of the predictions of the wind noise from the measured horizontal velocity spectrum above the canopy and in the canopy as well as the wind velocity profile above and in the canopy. The wind profiles measured in this study were not typical of those published in the meteorology literature due to their limited height and sparse regular planting. The height dependence of the 3-D turbulence spectra also differ from the model spectra. The modifications necessary to produce predictions for more typical forests from the meteorological literature will be described. [Work supported by the U. S. Army Research Office under grant W911NF-12-0547.]
Wind noise suppression using compact arrays of infrasound sensors
Authors: Frazier William G.
Published: May 2015

This presentation describes how a compact array (aperture much less than the shortest wavelengths of interest) of infrasound sensors can be used to significantly enhance signal detection and waveform estimation in the presence of high levels of wind noise without the use of unwieldy mechanical screening. The methodology's effectiveness is founded on the fact that wind noise can be highly correlated on short spatiotemporal scales. This correlation structure is adaptively estimated from data and is used to formulate a generalized likelihood ratio detection problem and a minimum mean squared error waveform estimation problem. The infrasoudnic waveform is explicitly represented by a user-definable, parametrically characterized, stochastic prior distribution. Choice of this prior can enhance detection of anticipated signals and suppress others and thus more than one prior can be utilized in order to perform some level of classification. The presentation provides typical performance results from a range of application scenarios. Application to more traditional infrasound arrays is also presented, illustrating that exploitation of only the temporal correlation properties of wind noise is also beneficial in the context of the stochastic models and estimation techniques utilized.
Comparisons of semi-porous fabric domes and cylindrical wind fence enclosures for infrasonic wind noise reduction
Authors: Abbott JohnPaul , Raspet Richard
Published: May 2015

This investigation compares the measured wind noise of two types of infrasonic wind noise reduction barriers. The first type is a set of 2.0 m diameter semi-porous fabric domes constructed and tested by the Army Research Laboratory [J. Acoust. Soc. Am. 136, 2139 (2014)]. The type second is a set of single and multi-layer cylindrically shaped variable-porous wind fence enclosures measuring 5.0 m and 10.0 m, constructed and tested by the National Center for Physical Acoustics [J. Acoust. Soc. Am. 134, 4161 (2013)]. Preliminary investigations showed that for wind speeds between 3—6 m/s the measured power spectra densities of the fabric domes were comparable to the measured power spectra densities of the single layer, 5.0 m diameter wind fence enclosures at mid-range porosities. The measured power spectra densities of the fabric domes were higher than the measured power spectra densities for the 10.0 m diameter and multi-layer wind fences enclosures. For wind speeds greater than 6 m/s, the measured wind noise for the fabric domes was comparable to or lower than the measured wind noise for the wind fence enclosures.
New calculation of the turbulence-turbulence contribution to wind noise pressure spectra by incorporating turbulence anisotropy
Authors: Yu Jiao , Zhu Yanying , Raspet Richard
Published: May 2015

Turbulence-turbulence interaction and turbulence-shear interaction are the sources of intrinsic pressure fluctuation for wind noise generated by atmospheric turbulence. In previous research [Yu et al., J. Acoust. Soc. Am. 129(2), 622–632 (2011)], it was shown that the measured turbulent fields outdoors can be realistically modeled with Kraichnan’s mirror flow model and turbulence-shear interaction pressure spectra at the surface were predicted and compared to measurements. This paper continues to apply Kraichnan’s model and calculates the turbulence-turbulence interaction wind noise pressure spectra under anisotropic turbulence conditions. Different from turbulence-shear interaction, the fourth-order moments of the turbulence are needed in the calculation. A new calculation of the turbulence-turbulence contribution to the wind noise pressure spectra is compared to that for isotropic turbulence and the results are analyzed. [Work supported by the U. S. Army Research Office (Grant No. W911NF-12-0547) and the National Natural Science Foundation of China (Grant No. 11304137).]