bluuebunny/crossref_metadata_2025 huggingface dataset:
Equal-latency curves and auditory weighting functions for bottlenose dolphins (Tursiops truncatus) and California sea lions (Zalophus californianus)
Authors: Mulsow Jason , Finneran James J. , Schlundt Carolyn E.
Published: May 2015

Reaction time (RT) data obtained from simple tonal detection tasks have been used to estimate frequency-specific equal-loudness contours in non-human animals. In order to guide the design of auditory weighting functions for marine mammals, equal-latency contours were generated using RT data from a simple tonal detection including two bottlenose dolphins (under water) and three California sea lions (in air). Median RT increased exponentially with decreased SPL in all cases. Equal-latency contours for near-threshold RTs were similar to audiograms in both species. Data for the sea lions showed some compression of equal-latency contours with increases in SPL; however, large inter-subject differences in the data for dolphins made results for that species more difficult to interpret. The equal-latency contours for all subjects progressively diverged from predicted equal-loudness contours at higher SPLs, likely a result of very small changes in RT with relatively large increases in SPL. As a result, the contours of most interest for designing weighting functions for high-level noise exposures were also the least reliable. The general similarity of most of the contours to species-typical audiograms suggests that more easily obtained auditory thresholds may provide useful approximations for weighting. [Funded by U.S. Navy Living Marine Resources Program.]
Acoustic tweezers: Manipulating particles, cells, and fluids using sound waves
Authors: Huang Tony Jun
Published: May 2015

The ability to manipulate cells, micro/nanoparticles, and fluids in a biocompatible and dexterous manner is critical for numerous biological studies and applications such as cell-cell communication, biosensing, tissue engineering, regenerative medicine, and lab on a chip. Here, we summarize our recent progress on an “acoustic tweezers” technique that utilizes acoustic waves to manipulate particles, cells, organisms, and fluids. This technique is capable of manipulating cells and microparticles regardless of shape, size, charge, or polarity. Its power intensity, approximately 107 times lower than that of optical tweezers, compares favorably with those of other active patterning methods. Cell viability, proliferation, and gene expression have revealed the technique to be extremely biocompatible. The aforementioned advantages, along with this technique’s simple design and low-cost, compact design, render the “acoustic tweezers” technique a promising tool for various applications in biology, chemistry, engineering, biophysics, and materials science.
Intense cavitation in microfluidics for bio-technology applications
Authors: Ohl Siew-Wan , Tandiono Tandiono , Klaseboer Evert , Ow Dave , Choo Andre , Ohl Claus-Dieter
Published: May 2015

This study reports the use of intense ultrasonic cavitation in the confinement of a microfluidics channel [1], and the applications that has been developed for the past 4 years [2]–[5]. The cavitation bubbles are created at the gas-water interface due to strong capillary waves which are generated when the system is driven at its natural frequency (around 100 kHz) [1]. These bubbles oscillate and collapse within the channel. The bubbles are useful for sonochemistry and the generation of sonoluminescence [2]. When we add bacteria (Escherichia coli), and yeasts (Pichia pastoris) into the microfluidics channels, the oscillating and collapsing bubbles stretch and lyse these cells [3]. In another application, human red blood cells are added to a microchamber. Cell stretching and rapture are observed when a laser generated cavitation bubble expands and collapses next to the cell [4]. A numerical model of a liquid pocket surrounded by a membrane with surface tension which was placed next to an oscillating bubble was developed using the Boundary Element Method. Lastly, new results on gene transfection [5], lysing of bacterial spores, and emulsification by ultrasonic bubbles will be presented. References: [1] Tandiono et al., Lab Chip 10(14), 1848–1855 (2010). [2] Tandiono et al., Proc. Natl. Acad. Sci. U.S.A. 108(15), 5996–5998 (2011). [3] Tandiono et al., Lab Chip 12(4), 780–786 (2012). [4] Tandiono et al., Soft Matter 9(36), 8687–8696 (2013). [5] Ling et al., Biotechnol. J. 9(8), 1081–1087 (2014).
Transition to turbulence in acoustically driven flows
Authors: Mehta Vineet , Thompson Charles , Chandra Kavitha , Denis Max
Published: May 2015

Direct numerical solutions of the three-dimensional time-dependent Navier-Stokes equation are presented for the evolution of three-dimensional finite-amplitude disturbances in the Stokes boundary layer. The basic flow is driven harmonically in time and the disturbances represent a departure from the basic state of the fluid. For fixed value of the fluid viscosity, instability is shown to be a function of the amplitude of oscillation of the basic flow, excitation frequency, and the channel wall geometry. Special attention is given to pressure gradient and surface wave driven flows. Conditions for instability and transition are outlined.
Signal coherence of broadband sound propagation through a refractive and turbulent atmosphere
Authors: Cain Jericho E. , Collier Sandra L. , Ostashev Vladimir E. , Wilson David K.
Published: May 2015

Atmospheric turbulence and refraction have significant effects on acoustic signals. The signal coherence can be directly measured and can yield information for use in source localization and classification; however, the effects of turbulence and refraction decrease the accuracy of such efforts. The signal coherence of a broadband acoustic signal above an impedance ground in a refractive, turbulent atmosphere with spatial fluctuations in the temperature and wind velocity is modeled and the results for several atmospheric cases are considered.
On the search of the optimal range and number of lags for an autocorrelation model of pitch
Authors: Ruiz-Blais Sebastian , Camacho Arturo
Published: May 2015

Autocorrelation-based pitch models account for a number of pitch phenomena. Previous work has demonstrated their successfulness in response to different stimuli, when combined with a model of the auditory nerve activity and summed across channels [Balaguer-Ballester, Denham & Meddis, J. Acoust. Soc. Am. 124, 2186–2195 (2008)]. However, autocorrelation models are generally thought of as biologically unrealistic because they require many calculations and might not tally with the neurobiological principle of economy. The present work consists of a series of simulations that aim to determine whether all operations required to compute autocorrelation are strictly necessary to account for the psychophysical data or not. To investigate this, different ranges and densities of lags are used, and the produced implementations are tested with stimuli comprising pure tones, resolved and unresolved complex tones, inharmonic complex tones, and click trains. As a result, the optimal range and number of lags is found, as the most economical setup that agrees with psychophysical evidence.
The build-up and resetting of auditory stream segregation: Effects of timbre, level, and abrupt change
Authors: Rajasingam Saima L. , Summers Robert J. , Roberts Brian
Published: May 2015

Two experiments explored the effects of timbre, level, and abrupt change on the dynamics of streaming. Listeners continuously monitored 20-s ABA-sequences (1-kHz base frequency; Δf = 4–8 semitones) and reported when the sequence was heard as integrated or segregated. Experiment 1 used pure tones and narrowly spaced (±25 Hz) tone pairs (dyads); both evoke similar excitation patterns but dyads have a “rougher” timbre. Dyad-only sequences induced a strongly segregated percept, with limited scope for further build-up. Abrupt alternations every 13 triplets produced large changes in the extent of segregation. Dyad-to-pure transitions produced substantial resetting, but pure-to-dyad transitions elicited greater segregation than for the corresponding time in dyad-only sequences (overshoot). Experiment 2 examined the effect of varying triplet level. Pure-tone sequences with a maintained 12-dB difference showed similar build-up, but an asymmetry occurred for alternating sequences. Increased-level transitions caused a significant reduction in segregation (resetting) whereas decreased-level transitions had little or no effect. The results suggest that timbre can strongly affect the likelihood of stream segregation, even without peripheral-channeling cues, but moderate level differences do not. Furthermore, abrupt changes in sequence properties have variable effects on the tendency to report segregation—including resetting, overshoot, and asymmetries in the effect of transition direction.
Individual differences in acoustic acuity at supra-threshold level
Authors: Dai Lengshi , Shinn-Cunningham Barbara G.
Published: May 2015

The ability to detect acoustic amplitude modulated envelopes differs even among listeners with normal hearing thresholds (NHTs), an effect that to some degree may correlate with noise exposure history. Moreover, at least one animal study suggests that auditory nerve fibers (ANFs) with lower spontaneous firing rates (high thresholds) are more vulnerable to damage from noise exposure compared to those with high spontaneous rate ANFs. Given that NHTs depend primarily on high-spontaneous rate fibers, even relatively severe loss of low-spontaneous ANFs could be present in listeners that have “normal hearing” according to traditional hearing screenings. Here, we evaluated the robustness of supra-threshold coding, which may relate to low-spontaneous ANFs health, in listeners with NHTs. Specifically, we measured the phase-locking-values (PLVs) of subcortical envelope following responses to SAM tones (carrier: 1500 Hz; modulation rate: 100 Hz) at two sensation levels (20/50 dB SL) and with two modulation depths (0/−6 dB). Results reveal huge individual differences in PLV strengths that are negatively correlated with behavioral amplitude modulation detection thresholds for noises at a moderate supra-threshold level (carrier: band-pass-filtered noise centered at 1500 Hz with 300 Hz bandwidth; modulation rate:10 Hz). Our data support the hypothesis that the number of operational low-spontaneous rate ANFs may differ human listeners with NHTs, and that deficit in low-spontaneous rate ANFs can lead to deficits in perceptual abilities.
Application of a monaural glimpsing model to binaural speech mixtures
Authors: Best Virginia , Mason Christine R. , Swaminathan Jayaganesh , Roverud Elin , Kidd Gerald
Published: May 2015

Under certain circumstances, listeners with sensorineural hearing loss demonstrate poorer speech intelligibility in spatially separated speech maskers than those with normal hearing. One important issue in interpreting these results is whether the target speech information is available or audible in the spatialized mixture. Simple energy-based “glimpsing” models can be used to quantify the available target in speech mixtures. For example, as target level decreases in a fixed-level masker, fewer and fewer good glimpses are available. Moreover, those glimpses may not all be above threshold, particularly for individuals with hearing loss. In this study we used a glimpsing model to isolate available target glimpses in binaural speech stimuli (separately for each ear) as a function of target-to-masker ratio. Performance for stimuli processed in this way was compared to binaural performance in listeners with normal hearing and listeners with hearing loss. Results suggest that binaural performance was partly limited by the ability to use the available glimpses. Increasing the level of the glimpses gave mixed results, which will be discussed in terms of audibility. [Work supported by NIH/NIDCD.]
Duration and transition effects in multiple-burst, multitone masking
Authors: Thompson Eric R. , Wisniewski Matthew G. , Iyer Nandini , Simpson Brian D.
Published: May 2015

Previous studies of tone detection using a multiple-burst same (MBS) or multiple-burst different (MBD) masker have shown that tone detection thresholds were lower with an MBD masker than with an MBS masker, and decreased as the number of bursts increased. In those studies, as the number of bursts increased, the total signal duration increased as well as the number of times the (MBD) masker changed frequencies. The present study was designed to differentiate between the effects of signal duration and masker transitions. In one condition, the burst duration was inversely varied with the number of bursts so that the overall stimulus duration was always 480 ms. In a second condition, the stimuli always had eight 60-ms bursts, but the number of times the masker transitioned from one random draw of frequencies to a different draw was varied from zero (MBS) to seven (MBD). The MBD condition showed a steady improvement with number of bursts, regardless of the burst duration. There was a similar improvement with the number of masker transitions. There was only a small improvement in thresholds with increasing burst duration. Results suggest that the number of changes of masker frequencies drives performance more than the total signal duration.
Impulsive sound localization using time-domain beamformer
Authors: Seo Dae-Hoon , Choi Jung-Woo , Kim Yang-Hann
Published: May 2015

This paper presents a beamforming technique for locating impulsive sound source in low signal to noise ratio (SNR). Impulsive sound generates a high peak-pressure for a short duration in time-domain. However, the measured signal of the sensor are always embedded in the interference noise sources and measurement noise, therefore, it is difficult to estimate the direction of arrival of impulse sound in low SNR environment. In contrast to a frequency-domain beamformer, it has been reported that a time-domain beamformer can be better suited for transient signals. We proposes peak and crest factor as alternative directional estimators to enhance the performance of a time-domain beamformer in view of the fact that impulsive sound has high peak sound pressure as well as short duration time compared to the ambient noise sources. The performance of three directional estimators, the peak, RMS, and crest factor of output values, are investigated and compared with the incoherent measurement noise embedded in multiple microphone signals. The proposed formula is verified via experiments in an anechoic chamber using a uniform linear array, and the results show that the crest factor estimation of beamformer output determines the direction in a low SNR condition in which interference sources are dominants.
Modal response of a simply supported plate driven by a single, asymmetric piezoelectric actuator for use as a flat-panel loudspeaker
Authors: Heilemann Michael C. , Bocko Mark F.
Published: May 2015

An approximate analytical solution for the mechanical response of a thin plate to a single, asymmetrically bonded piezoelectric driver has been found. Previous work has focused only on the response of plates driven by symmetrically aligned actuators or for beams with drivers bonded to one side. The relative magnitudes of extensional and flexural waves produced by the single-sided driver configuration were determined as a function of the physical parameters of the plate and driver. The modal response of flexural waves for a simply supported thin plate also was determined. Interactions at the plate boundaries with the support structure may convert extensional waves into sound-producing flexural waves, which can lead to audio distortion. A non-moment inducing support scheme with high damping is proposed to minimize this effect.
Characterization of the dominant structural vibration of hearing aid receivers
Authors: Varanda Brenno , Miles Ron N. , Warren Daniel
Published: May 2015

The overall aim of this research is to analyze and characterize the mechanical vibration of hearing aid receivers, a key electro-acoustic component of hearing aids. The receiver is a high efficiency miniature sound source which utilizes a balanced armature electromagnetic motor. A standard side effect for most balance armature receivers is structural vibration. This receiver-borne structural vibration can travel through the hearing aid package to the microphones, resulting in undesirable oscillations, just like acoustic feedback. To better understand and control this important source of feedback in hearing aids, a simple dynamic model has been developed to describe the system. The model consists of two rigid bodies connected by a torsional spring and damper. A method was developed to estimate the parameters for the dynamic model using experimental data. The data were collected using translational velocity measurements using a scanning laser vibrometer of a Knowles ED-series receiver on a complaint foundation. The analytical dynamic model was validated with finite element analysis using COMSOL and the multibody dynamics module.
Effects of age, hearing loss, and linguistic complexity on listening effort as measured by working memory span
Authors: Pichora-Fuller Margaret K. , Smith Sherri L.
Published: May 2015

Listeners, especially older or hard-of-hearing individuals, report that understanding conversation in noisy situations is effortful. Individual differences may be due to auditory and/or cognitive processing abilities. It is assumed that auditory processing depends on the individual’s degree and type of hearing loss, while cognitive processing depends on the individual’s working memory (WM) capacity. Many researchers have measured reading WM span to minimize the effects of hearing loss; however, variations due to hearing loss may be important in assessing processing demands (listening effort) during speech-in-noise understanding. The effects of the acoustical properties of the signal and masker on listening effort have been studied, but less is known about the effects of the linguistic complexity of the materials. We predicted that demands on WM and the correlation between WM span measures and speech-in-noise performance would increase with increasing linguistic complexity, with speech-in-noise performance correlating more strongly with auditory than with visual measures of WM span. To test these hypotheses, we administered speech tests varying in linguistic complexity and measures of both reading and listening WM span. Participants were a group of younger listeners with normal hearing and a group of older listeners with bilateral sensorineural hearing loss.
Verbal response time in children systematically varies with the spectral resolution of speech
Authors: Ward Kristi M. , Shen Jing , Souza Pamela E. , Grieco-Calub Tina M.
Published: May 2015

Children require higher spectral resolution to perform comparably to adults on speech recognition tasks. A potential source of this age-related difference is children’s immature cognitive processing. Verbal response time (VRT), the speed at which listeners verbally repeat speech stimuli, has been used as a correlate of cognitive load (or listening effort, LE) in children: listeners exhibit faster VRT in conditions with greater signal-to-noise ratios and slower VRT in conditions with decreased audibility. If VRT is representative of changing cognitive demands during speech recognition, and therefore changing LE, in children, we predict that gradually decreasing the spectral resolution of the speech signal will result in a concomitant slowing of VRT. To test this prediction, we measured VRT in typically developing children (8–12 years old) while they performed a sentence recognition task that was either unprocessed (full spectral resolution) or noiseband vocoded with 4, 6, or 8 spectral channels. Preliminary data suggest that children’s VRT varies systematically with spectral resolution: VRT slows with decreasing spectral resolution of the speech signal. These results are consistent with the idea that VRT is a sensitive measure of LE in children. Discussion will consider these data in the context of other methods of measuring LE.
Honking is just noise (or just about): The effect of energetic masking on recognition memory for spoken words
Authors: Strori Dorina , Zaar Johannes , Scharenborg Odette , Cooke Martin , Mattys Sven
Published: May 2015

Previous research indicates that listeners encode both linguistic and indexical specifications of the speech signal in memory. Recent evidence suggests that non-linguistic sounds co-occurring with spoken words are also incorporated in our lexical memory. We argue that this “sound-specificity effect” might not be due so much to a word-sound association as to the different acoustic glimpses of the words that the associated sounds create. In several recognition-memory experiments, we paired spoken words with one of two car honk sounds and varied the level of energetic masking from exposure to test. We did not observe a drop in recognition accuracy for previously heard words when the paired sound changed as long as energetic masking was controlled. However, when we manipulated the temporal overlap between words and honking to create an energetic masking contrast, accuracy dropped. The finding suggests that listeners encode irrelevant non-speech information in memory, but only in certain contexts. Calling for an expansion of the mental lexicon to include non-speech auditory information might be premature. Current work is investigating the effect in non-native listeners of English, and whether maskers that are more integral to the words and hence more difficult to segregate lead to a more robust effect.
Study of the maximum signal-to-noise-ratio filters for single- and multi-channel noise reduction
Authors: Chen Jingdong , Huang Gongping , Benesty Jacob
Published: May 2015

Noise reduction is a problem of recovering a speech signal of interest from its noisy observations. Since the objective of the problem is to reduce noise, thereby improving the signal-to-noise ratio (SNR), it is natural to consider the use of maximum SNR filters. However, the maximum SNR filters, if not designed properly, may introduce significant speech distortion, leading to speech quality degradation instead of improvement. This paper investigates the design of maximum SNR filters for noise reduction with minimum speech distortion. It covers the following design cases: (1) single-channel noise reduction in the time domain; (2) multichannel noise reduction in the time domain; (3) single-channel noise reduction in the short-time-Fourier-transform (STFT) domain with or without interframe information; (4) multichannel noise reduction in the STFT domain with or without interframe information. A large number of experiments are performed to illustrate the properties of these maximum SNR filters.
High frequency source localization in a shallow ocean sound channel using frequency-difference matched field processing
Authors: Worthmann Brian M. , Dowling David R.
Published: May 2015

Matched field processing (MFP) is an established technique for locating remote acoustic sources in known environments. Unfortunately, environment-to-propagation model mismatch prevents successful application of MFP in many circumstances, especially those involving high frequency signals. For beamforming applications, this problem was found to be mitigated through the use of a nonlinear array-signal-processing technique called frequency difference beamforming (Abadi et. al. 2012). Building on that work, this nonlinear technique was extended to Bartlett MFP, where ambiguity surfaces were calculated at frequencies two orders of magnitude lower than the propagated signal, where the detrimental effects of environmental mismatch are much reduced. Previous work determined that this technique has the ability to localize high-frequency broadband sources in a shallow ocean environment with a sparse vertical array, using both simulated and experimental propagation data. Using simulations, the performance of this technique with horizontal arrays and adaptive signal processing techniques was investigated. Results for signals with frequencies from 10 kHz to 30 kHz that propagated in a 100-m-deep shallow ocean sound channel with a downward refracting sound speed profile will be shown for source array ranges of one to several kilometers. [Sponsored by the Office of Naval Research.]
Bayesian linearized two-hydrophone localization of a pulsed acoustic source
Authors: Skarsoulis Emmanuel , Dosso Stan E.
Published: May 2015

A three-dimensional localization method for transient acoustic sources is developed, based on time differences between direct and surface-reflected arrivals at two hydrophones. The method accounts for refraction caused by a depth-dependent sound-speed profile using a ray-theoretic approach, and, further, it provides localization error estimates accounting for uncertainties of the arrival times and hydrophone locations, as well as for depth-dependent uncertainties in the sound-speed profile. In the first of two steps, source depth and range to each hydrophone are estimated using an iterative, linearized Gauss-Markov inversion scheme. In the second step, the estimated source ranges are combined with the hydrophone locations to obtain the source location in the horizontal. Localization performance is analyzed in a simulation study, and the linearized localization estimates and uncertainties are validated by comparison with a fully-nonlinear (but numerically intensive) Markov-chain Monte Carlo inversion. [Work supported by Aristeia-II program, EU-ESF and Greece, NSRF 2007-13.]
A deep-water experiment to measure mid frequency attenuation
Authors: Tippmann Jeffery D. , Sarkar Jit , Roux Philippe , Hodgkiss William S. , Kuperman William A.
Published: May 2015

A deep-water experiment was performed off the west coast of the United States with a short vertical array cut for 7.5 Hz and a source transmitting tonals as well as chirps. The data were processed to identify eigenray arrivals out to a convergence zone for the ultimate purpose of revisiting mid frequency, deep water volume attenuation in the Pacific Ocean and comparing it to decades old measurements and models. Further, aside from the beamforming done at the receiver array, attempts were made to construct a synthetic aperture source array in order to perform “double beamforming” and thereby enhance the signal to noise ratio. We present our initial results of this experiment.
Geo-acoustic inversion of marine sediments using vector sensor measurements
Authors: Dall'Osto David , Dahl Peter H.
Published: May 2015

In this paper, a narrow-band geo-acoustic inversion scheme based on the acoustic vector field is presented. Measurements of acoustic particle velocity made with a vector sensor and short line array of hydrophones are studied with regards to the interference pattern generated by single 1–4 kHz source. This source was lowered from a research vessel positioned within three water depths (depth 20-m) of the receivers, and projected a series of 100-ms long continuous wave (cw) pulses as it was raised toward the surface. The interference pattern measured at the receivers is assessed by a non-dimensional property of the acoustic particle velocity, the degree of circularity [Dall’Osto and Dahl, J. Acoust. Soc. Am. 134, 109 (2013)], computed directly at the vector sensor and approximated along the line-array. This degree of circularity is highly sensitive to the phase of interfering multipaths, which depends on both the source-receiver geometry and the geo-acoustic properties of sea-bed. Source positions measured by GPS and depth sensors are used to model the time-dependent particle velocity field as the cw tone establishes a steady-state response. A best-fit model to the field data provides an estimate of the geo-acoustic properties of the sandy sediment at the experimental site.
Localization for broadband source by a single vector sensor in shallow water
Authors: Shi Junjie , Sun Dajun , Lv Yunfei , Yu Yun
Published: May 2015

The physical meaning of array invariant is the absolute traveling time of different modal from a source to a receiver under the average sound speed. It can be gotten by the derivative of the arriving time against the corresponding cosecant function of elevation angle for each modal, which can be used for the passive source localization. A vector sensor can be seen as a small volumetric array. It has its capability of elevation angle determination to describe the multi-modal propagation and the single-modal dispersion in shallow water, which may imply a chance to get the array invariant for the source localization. Here, we take advantage of the dispersion based short time Fourier transform and warping transform techniques for the time-frequency analysis of vector sensor signals. This technique can improve acoustic normal mode identification and thereby extract the modal data more accurately for array invariant determination. The idea had been effectively validated during the experiment that took place in October 2014 in South China Sea of nearly 100 m depth. [Work supported by the National 863 Project (No. 2011AA090502) and National Natural Science Funds Program (No. 11404406).]
A tribute to Karl Kryter
Authors: Pearsons Karl S.
Published: May 2015

Karl Kryter came to Bolt Beranek and Newman in 1957 from Harvard to lead the Psycho-Acoustics Department. At that time, commercial aviation was transitioning from propeller driven aircraft to jet powered aircraft, like the Douglas DC8 and the Boeing 707. Public concern about the perceived increase in noise prompted the development of noise metrics. These new metrics provided better correlation with judged annoyance than overall sound levels; thus, perceived noise level (PNL) in PNdB units was introduced as a measure of airplane noise. He also contributed to establishing noise levels which may cause permanent hearing loss. Another interest was in creating a device that masked the noise of a dentist's drill. It was called the audio-analgesic. The last time I saw Karl was when we represented opposite sides in a court case. It was about the noise level of a medivac helicopter landing on a hospital roof. He was a wonderful boss and friend, a true role model. Fellow colleagues had only praise for him and the work environment he created. Born in 1914, he almost made it to 100 years, passing in 2013.
Neurophysiological effects of noise-induced hearing loss
Authors: Heinz Michael G.
Published: May 2015

Noise over-exposure is known to cause sensorineural hearing loss (SNHL) through damage to sensory hair cells and subsequent cochlear neuronal loss. These same histopathological changes can result from other etiological factors (e.g., aging, ototoxic drugs). Audiologically, each is currently classified as SNHL, despite differences in etiology. Functionally, noise-induced hearing loss can differ significantly from other SNHL etiologies; however, these differences remain hidden from current audiological diagnostic tests. For example, noise-induced mechanical damage to stereocilia on inner- and outer-hair cells results in neurophysiological responses that complicate the common view of loudness recruitment. Also, mechanical effects of noise overexposure appear to affect the tip-to-tail ratio of impaired auditory-nerve-fiber tuning curves in ways that create a much more significant degradation of the cochlear tonotopic representation than does a metabolic form of age-related hearing loss. Even temporary threshold shifts due to moderate noise exposure can cause permanent synaptic loss at inner-hair-cell/auditory-nerve-fiber synapses, which reduces neural-coding redundancy for complex sounds and likely degrades listening in background noise. These pathophysiological results suggest that novel diagnostic measures are now required to dissect the single audiological category of SNHL to allow for better individual fitting of hearing aids to restore speech intelligibility in real-world environments. [Work supported by NIH.]
The effects of noise on physician cognitive performance in a hospital emergency department
Authors: Dodds Peter , Xiang Ning , Sykes David , Triner Wayne , Sinclair Linda
Published: May 2015

The contemporary hospital emergency department presents a noisy and distracting sonic environment. While previous research has shown that the highly variable and overloud soundscape of hospitals leads to increased annoyance and physical stress for hospital employees, there is a need to objectively quantify the cognitive effects of noise on healthcare providers, particularly physicians. An ongoing collaborative research effort by the authors seeks to better understand and measure the cognitive and psychoacoustic effects of noise in a busy urban emergency department. Using binaural room-acoustic measurements and psychoacoustic modeling, the soundscape of the emergency department at Albany Medical Center has been analyzed. Through the use of the n-Back cognitive test and calibrated binaural recordings and room-simulations, we are examining the effect of a variety of sonic phenomena on the working memory and cognitive control of emergency department physicians at the Albany Medical Center at various points throughout their shifts. This paper will discuss methods for in situ cognitive testing, preliminary results, and review possible interventions and their efficacy in reducing noise and distractions for physicians in the emergency department.
Are the mechanisms for stream segregation shared among anurans and other tetrapods?
Authors: Christensen-Dalsgaard Jakob
Published: May 2015

Many male anurans (frogs and toads) call in large aggregations. Since the fundamental task of anuran auditory communication probably is to attract and localize potential mates, segregation of the callers is likely an important task for the auditory system. Behavioral experiments have shown that elements of stream segregation, based on frequency separation and spatial separation, can be demonstrated in anurans. The neural processing of these cues is interesting, because most auditory processing probably takes place in the midbrain torus semicircularis (TS, homolog to the inferior colliculus). It has been shown that spatial release from masking is sharpened by 6 dB in the TS, and that neurons in the TS are selective for call rates and number of call pulses. However, recently electrical stimulation of thalamic structures have demonstrated possible attentional modulation of TS responses that could also function in stream segregation. The modulation was call-specific and could also enhance binaural cues. In conclusion, many of the elements involved in auditory segregation in other animals are also found in anurans. However, it is uncertain whether the underlying mechanisms are similar. One crucial element in primate sound segregation—the representation of the competing streams in the neural responses—has so far not been demonstrated in anurans, and the most robust elements of stream segregation is really based on frequency processing, a relatively simple and ubiquitous property of most auditory systems.
Measurement and control of vocal interactions in songbirds
Authors: Hahnloser Richard
Published: May 2015

One obstacle for investigating vocal interactions in vertebrate animals is difficulty of discriminating individual vocalizations of rapidly moving, sometimes simultaneously vocalizing individuals. To overcome this obstacle, we have developed an ultra-miniature back-attached sound/acceleration recording system that allows perfect separation of birdsong vocalizations irrespective of background noise and the number of vocalizing animals nearby. With this system, we have been able to identify hierarchies in the vocal interactions among adult male and female zebra finches. Furthermore, to causally interfere with vocal interactions in groups of up to four birds, we have developed an echo cancelation system that allows us to have full digital control of vocal interactions between any bird pair. With these tools, we hope to be able to further advance the dissection of vocal communication in songbirds.
Radial excursions of bound and non-bound targeted lipid-coated single microbubbles
Authors: van Rooij Tom , van der Steen Antonius F. , de Jong Nico , Kooiman Klazina
Published: May 2015

One of the main challenges for ultrasound molecular imaging is acoustically distinguishing non-bound microbubbles from those that have bound to their molecular target. We previously showed that biotinylated DPPC-based microbubbles (16 C-atoms) had a larger binding area and a more domed shape when bound to a streptavidin-coated surface than DSPC-based microbubbles (18 C-atoms) [1]. In the present in vitro study, we used the Brandaris 128 ultrahigh-speed camera (~15 Mfps) to compare the acoustical responses of biotinylated DPPC and DSPC-based microbubbles in a non-bound configuration and bound to a streptavidin-coated membrane, aiming to acoustically discriminate them from each other. The microbubbles were driven at a pressure of 50 kPa and at frequencies between 1 and 4 MHz. The main difference between bound and non-bound microbubbles was the lower radial excursion at the fundamental frequency for bound microbubbles. Resonance frequencies and subharmonic responses were the same for bound and non-bound microbubbles. Finally, at the second harmonic frequency, we found higher relative radial excursions for bound DSPC-based microbubbles than for non-bound DSPC microbubbles, whilst there was no difference for DPPC-based microbubbles. This might provide opportunities to acoustically discriminate bound from non-bound DSPC microbubbles. [1] Kooiman et al., Eur. J. Lipid Sci. Technol. (2014).
An in vitro study of subharmonic emissions from monodisperse lipid-coated microbubbles
Authors: Li Qian , Burgess Mark , Porter Tyrone
Published: May 2015

Subharmonic imaging is an ultrasound imaging method which utilizes the subharmonic response of a contrast agent to ultrasound excitation. It is possible to achieve high agent-to-tissue contrast because tissues do not emit subharmonic signals. In this project, we investigated the relationship between subharmonic emissions from monodisperse lipid-coated microbubbles and acoustic pressure. First, the resonance frequency for monodisperse microbubble suspension was determined from attenuation spectra measured using a through-transmission technique. Next, the microbubbles were excited at the resonance and at twice the resonance frequency. A transducer positioned orthogonal to the excitation transducer was used to detect acoustic emissions from the microbubbles at half the excitation frequency. It was found that the pressure required for subharmonic emissions was lower when monodisperse microbubbles were excited at twice the resonance frequency. For example, 6.5μm diameter microbubbles with a resonance frequency of 1.4 MHz had a pressure threshold for subharmonic emissions of approximately 30 kPa at 2.8 MHz excitation while those excited at 1.4 MHz could not be forced into subharmonic oscillations for the pressure range we used in this study (i.e., below 150 kPa). Implications of these results on the use of monodisperse lipid-coated microbubbles for subharmonic imaging will be discussed.
Singular value decomposition: A better way to analyze cavitation-noise data
Authors: Chitnis Parag V. , Farny Caleb , Roy Ronald A.
Published: May 2015

Detection of inertial and stable cavitation is important for guiding high-intensity focused ultrasound (HIFU). Acoustic transducers can passively detect broadband noise from inertial cavitation and the scattering of HIFU harmonics from stable cavitation bubbles. Conventional approaches to separating these signals typically involve a custom comb-filter applied in the frequency domain followed by an inverse-Fourier transform, which cannot be implemented in real-time. We present an alternative technique based on singular value decomposition (SVD) that efficiently separates the broadband emissions and HIFU harmonics in a single step. Spatio-temporally resolved cavitation detection was achieved using a 128-element, 5-MHz linear-array system operating at 15 frames/s. A 1.1-MHz transducer delivered HIFU to tissue-mimicking phantoms for a duration of 5 s. Beamformed radiofrequency signal corresponding to each scan line and frame were assembled into a matrix and SVD was performed. Eigen vectors that corresponded to HIFU harmonics were identified as ones whose spectrum contained a peak centered at one of the harmonic frequencies. The projection of data onto this eigen-base produced the stable-cavitation signal. The remaining eigenvectors were used to obtain the inertial-cavitation signal. The SVD-based method faithfully reproduced the structural details in the spatio-temporal cavitation maps produced using the comb-filter albeit with marginally lower SNR.
Effect of blood viscosity and thrombus composition on sonoreperfusion efficacy
Authors: Black John , Schnatz Frederick , Yu Francois T. , Chen Xucai , Brands Judith , Villanueva Flordeliza , Pacella John
Published: May 2015

Embolization during stenting for myocardial infarction (MI) causes microvascular obstruction (MVO). We demonstrated that ultrasound (US) and microbubble (MB) therapy [sonoreperfusion (SRP)] resolves MVO from venous microthrombi at plasma viscosity. However, blood is more viscous than plasma, and arterial microthrombi are mechanically distinct from venous clot. We tested whether blood viscosity and arterial microthrombi decrease SRP efficacy in our in vitro model of MVO. Lipid MB in plasma and blood viscosity PBS were passed through a 40 μm pore mesh. Arterial microthrombi were formed in a Chandler loop. Venous microthrombi were made statically. MVO was created by occluding the mesh with microthrombi until upstream pressure reached 40 mmHg. US (1 MHz; 5000 cycles; 0.33 Hz PRF; 0.6, 1.0, and 1.5 MPa peak negative pressure) was delivered with a single focused element transducer. MVO caused by arterial thrombi at increased viscosity resulted in less upstream pressure drop during therapy. PCD showed a decrease in inertial cavitation (IC) when viscosity was increased. SRP efficacy is less with arterial thrombi compared to venous thrombi, and higher viscosity further reduces SRP efficacy by decreasing IC. These findings could help guide the selection of US parameters for in vivo optimization of SRP.
Subharmonic threshold quantification of ultrasound contrast agents
Authors: Hayashi Rintaro , Allen John S. , Chitnis Parag , Ketterling Jeffrey A.
Published: May 2015

The measurement and prediction of the subharmonic threshold of ultrasound contrast agents is of significant interest, particularly for high frequency applications. Theoretical analytical predictions typically follow from a weakly nonlinear analysis assuming continuous, single frequency forcing. Furthermore, numerical simulation and experimental definitions are often based on the quantification of spectral response of the nonlinear harmonics. Limitations of these approaches are investigated with respect to pulsed forcing and associated non-stationary (chirp) excitations. Novel quantification and definitions are proposed with respect to instantaneous frequency and relative energy content of an empirical mode decomposition of the scattered pressure. Teager-Kasiser energy operator allows for additional quantification. The methodology is examined with respect to experimental polymer contrast agent data.
Stress and strain fields produced by violent bubble collapse
Authors: Mancia Lauren , Vlaisavljevich Eli , Warnez Matthew , Xu Zhen , Johnsen Eric
Published: May 2015

Cavitation finds a key application in therapeutic ultrasound. For example, histotripsy relies on the rapid expansion of cavitation bubbles to fractionate soft tissue. To fully understand the mechanisms responsible for tissue fractionation, we numerically model cavitation in a tissuelike medium, focusing on the effect of its viscoelastic properties (viscosity, elasticity, and relaxation). It is hypothesized that ablation is caused by high strain rates and stresses exerted on the surrounding tissue as bubbles rapidly expand from nanometer to micron scales. The present study uses robust numerical techniques to compute the stress fields in the surrounding medium produced by single-bubble expansion. Bubble expansion is driven by a waveform that approximates a histotripsy pulse with relevant parameters, and soft tissue surrounding the bubble is modeled as a viscoelastic medium with Neo-Hookean elasticity. We will examine the stress, strain, and temperature fields produced during this process to explain potential damage mechanisms.
The character of noise and its relation to noise effects
Authors: Fiebig André
Published: May 2015

The existence of noise effects leading to adverse health effects is beyond controversy. However, the main factors responsible for specific noise effects are still not clear. The human hearing system does not only register the sound pressure level of noise. It shows a high performance in amplitude, frequency, and time resolution and recognizes patterns in noise. Interestingly, several physiological reactions are not only influenced by the sound pressure level of noise. Due to certain psychoacoustic properties of noise or the level of noise annoyance stronger physiological reactions are stimulated. In order to predict responses to noise more reliably, psychoacoustic parameters and further hearing related-parameters have to be applied. Moreover, it is decisive to distinguish between auditory sensation and sound perception. Sound perception refers to complex processes, where additional information is processed and “mixed” with basic auditory sensations. Sound perception implies the cognitive processing, interpretation, and assessment of sound. Some studies suggest that the sound perception dimension is highly relevant to evoked physiological reactions and noise effects. The paper illustrates the difference between auditory sensation and sound perception and highlights the need to analyze sound in terms of perception to understand noise effects more in detail.
The operating theater—A paying challenge for soundscape design
Authors: Sauer Holger
Published: May 2015

The operating theater (OT) is virtually a parade example of a place with a high stress potential—not only for the working personnel but also for the patients. The reasons for this phenomenon are complex, and, partially inescapable. But since evidence reveals more and more the devastating consequences of this kind of stress for all persons concerned, there are good reasons to eliminate or at least reduce as many stress factors as possible. The soundscape is one of the major items which can work both stressing and de-stressing, however, quite diverging and dependant on the need and preferences of the several players. It is not sufficient simply to reduce the acoustic level since sound has different implications for the respective persons. Instead, the OT of the future requires a differentiated soundscape—implying hardware, software, and strategical patterns—which can be used in a more individualized way and, in addition, is adaptable to the respective circumstances. In order to achieve this, major efforts are required, among others due to complex preconditions; but it can be expected that these efforts will yield worthwhile results, which even will be transferable to other stress-sensitive domains.