bluuebunny/crossref_metadata_2025 huggingface dataset:
Advanced acoustic demonstration videos for higher education: Longitudinal wave motion.
Authors: Astrom Robert
Published: July 2011

In education every subject requires a unique instructional approach. Unlike English or mathematics, science based classes such as chemistry and physics cannot be taught effectively with lesson plans based solely on reading and homework assignments. These subjects require active learning through demonstrations and/or hands on experiments. That said some valuable experiments are too dangerous or costly to be feasible in all programs. The intent of this project is to advance the knowledge of and interest in acoustics by providing educators with interesting and educational videos of science based acoustic demonstrations and experiments which fit these situations. One of the most difficult concepts for educators to teach and students to understand is longitudinal wave motion. The videos presented are designed to illustrate longitudinal wave propagation using what many would consider dangerous or costly experiments. In keeping with the spirit of cost control the series of videos are to be provided to educators free of charge.
Time domain visualization of uniform spherical waves in a cavity using the method of wave images.
Authors: Ginsberg Jerry H.
Published: July 2011

The method of wave images uses the principle of superposition in conjunction with d’Alembert’s solution of the wave equation to construct time domain solutions. The formulation has been applied to describe the response in 1-D rectilinear waveguides for nonzero initial conditions [J. H. Ginsberg, J. Acoust. Soc. Am. 119, 1954–1960 (2006)] and forced motion at a boundary [J. H. Ginsberg, POMA 6, 025002 (2009)]. The present work extends the concept to describe the interplay of point-symmetric converging and diverging spherical waves in a cavity. It is shown that the responses to nonzero initial conditions, a source at the center, and motion at the boundary may be constructed from wave images for five elementary solutions that combine converging and diverging waves. The general solutions that are derived provide useful benchmarks that upper-level students may employ to verify frequency domain modal solutions. Furthermore, the ability to visualize an acoustical signal within a cavity as the time domain superposition of propagating waves provides a different, and in some respects more physically intuitive, perspective in comparison to frequency domain solutions.
Acoustic pulses in the atmosphere: An outdoor teaching laboratory.
Authors: Gabrielson Thomas B.
Published: July 2011

For the past two years, the Penn State Acoustic Data Measurements and Analysis course has incorporated several outdoor-sound exercises. One of these exercises is particularly amenable to illustrating concepts in acoustic propagation, signal design, and signal detection. Using relatively inexpensive hardware, student-designed pulse sequences are transmitted, received, and recorded in various outdoor environments. The advantages and disadvantages of large-bandwidth pulses are readily apparent. The students can perform replica correlation or matched filter processing and compare the achieved results to theoretical performance. The effects of the transmitting transducer on pulse shape are seen easily. Variability in the atmospheric propagation path, multipath, and upwind/downwind effects can be demonstrated as well as the impact of ambient noise on pulse detection. In addition, pulses can be reflected from moving objects (buses, for example) either for analyzing Doppler shift or for experimenting with Doppler-tolerant detection. Waveform types range from simple sinusoidal pulses to frequency-modulated pulses and frequency- or phase-shift coded maximum-length sequences to reproductions of animal vocalizations. In the fall of 2010, 40 students participated in this exercise: 20 resident students and 20 distance-education students.
National occupational research agenda for noise: What we know and what we still need to know.
Authors: Suter Alice H. , Themann Christa
Published: July 2011

The white paper generated by the original hearing loss prevention team of the National Occupational Research Agenda (NORA) has been revised and updated. In the process, important recent research results have come to light; some of them opening up new questions. Unfortunately some of the old questions remain unanswered. This paper will summarize some of the unanswered questions and concentrate on various new findings as well as research needs in areas such as impulse noise assessment, the interaction of noise and aging, the effects of noise on communication and safety, tinnitus, extra-auditory effects, and the evaluation of hearing conservation programs. There will always be areas about which knowledge is insufficient, but there are also salient reasons why action must be taken to prevent unwanted consequences.
Evaluating the effectiveness of interventions to control noise and work-related hearing loss.
Authors: Morata Thais C.
Published: July 2011

The objective of this presentation is to discuss the literature and recommendations on the evaluation of the effectiveness of interventions to control noise and prevent hearing loss. The American Recovery and Reinvestment Act of 2009 included a provision for federal funding to investigate how different interventions stack up against each other. The Act called on the Institute of Medicine to recommend a list of priority topics to be the initial focus of a new national investment in comparative effectiveness research. The need for research on hearing loss was placed in the highest priority group. Two recent Cochrane Reviews addressed the effects of interventions for the prevention of work-related hearing loss. Those concluded that some interventions improve the mean use of hearing protection devices compared to non-intervention; that there is low quality evidence that legislation can reduce noise levels in workplaces and contradictory evidence that prevention programs are effective in the long-term. There is consensus that most interventions focus on the use of hearing protection devices, and effectiveness depends on the quality of the implementation. Even though case studies show that substantial noise control can be achieved in the workplace, there is no evidence of this practice in the scientific literature.
The sources and effects of noise exposure in motorcyling.
Authors: Carley Michael , Kennedy John , Holt Nigel , Walker Ian
Published: July 2011

We report on the Bath Motorcycle Collaboration, an interdisciplinary collaborative research effort involving the Departments of Mechanical Engineering and Psychology at the University of Bath and Bath Spa University in the United Kingdom. The group has taken a broad approach to the problem of noise in motorcycling, examining its sources, transmission, and effects. Noise-induced hearing loss is a problem which can affect professional riders and racers as well as leisure riders and commuters. To study the problem, extensive wind tunnel tests have been conducted to provide detailed aerodynamic measurements and flow visualization around the helmet. These results have then been compared with and validated using on-track data covering realistic riding conditions. Insertion loss measurements combined with loudness matching tasks on groups of volunteers have been used to investigate the process of noise transmission through the head/helmet system. Hearing threshold shift measurements have been conducted to quantify the effects of this type of noise exposure on riders. This comprehensive approach has yielded valuable information for rider safety and has helped identify the research questions which will lead to a proper understanding of this important health and safety issue.
Modeling for remote acoustic characterization of gas hydrates.
Authors: Ivakin Anatoliy N.
Published: July 2011

Hydrates have a strong effect on elastic properties of the seafloor and their spatial (vertical and lateral) variability. The contrast in velocity created by the hydrate-cemented zone produces a strong seismic and acoustic reflection, the “bottom simulating reflection,” which is commonly used to locate gas hydrate deposits. Gas-hydrate-cemented strata also act as seals for trapped free gas. Hydrates may form complicated three-dimensional (3-D) structures and inclusions, such as nodes, veins, and flakes, resulting in significant volume heterogeneity of the sediment. This may cause a strong impact on the seabed scattering properties. Currently existing models of scattering from heterogeneous sea beds can be used for predicting this impact, and also serve as a base for development of new algorithms for remote acoustic characterization of gas hydrates and monitoring their stability. This possibility is discussed, and examples of such modeling are presented.
Active multibeam sonar-derived bubble plume fluxes and dynamics.
Authors: Leifer Ira , Luyendyk Bruce P. , Culling Dan
Published: July 2011

By their nature, seeps are spatially and temporally variable and episodic; thus, effective emissions’ quantification presents significant challenges because local measurements likely are unrepresentative. A multibeam sonar system was developed to observe ebullition spatially and used to study water column bubble plume processes, as well as subsurface migration processes for seepage from the Coal Oil Point seep field and the East Siberian Arctic Sea is presented. The system is designed for deep-sea application related to hydrates as part of a benthic observatory.
Laboratory measurements on gas hydrates and bubbly liquids using active and passive low-frequency acoustic techniques.
Authors: Greene Chad A. , Wilson Preston S. , Coffin Richard B.
Published: July 2011

The unique molecular structures of gas hydrates result in curious acoustic properties, which have yet to be adequately described. Understanding the acoustic behavior of stable and dissociating gas hydrates in liquids is vital for their localization and quantification using seismic or echosounding techniques. Further, with improved characterization of the acoustic properties of gas hydrates and bubbly liquids containing methane gas, acoustic methods may become an invaluable tool for monitoring hydrate dissociation and determining the magnitude of its effects on climate change. Acoustic properties of gassy substances are known to have a strong dependence on excitation frequency; however, tabulated values of hydrate material properties are most often measured in the frequency range of hundreds of kilohertz, while natural hydrate deposits and gas seeps are typically surveyed at seismic frequencies several orders of magnitude below laboratory measurement frequencies. This presentation details laboratory experiments in which a low-frequency (10 Hz–10 kHz) acoustic resonator apparatus was used to measure (a) sound speeds of bubbly liquids containing ideal and real gases and (b) bulk moduli and dissociation pressures of natural structure I and structure II gas hydrate samples. [Work supported by the Office of Naval Research.]
Motorcycle helmets and the frequency dependence of temporary hearing threshold shift.
Authors: Holt Nigel , Walker Ian , Kennedy John , Carley Michael
Published: July 2011

Temporary hearing threshold shifts (THTSs) as a result of exposure to noise vary as a function of the noise’s spectral content. However, to date THTS has been measured and predicted in a way that does not take account of frequency variation—most notably in standards such as British Standard 5330. We therefore carried out pure-tone audiometry on participants before and after exposure to white noise in order to quantify the frequency dependence of the THTS. Moreover, as this research group has previously shown that motorcycle helmets act as spectral filters, attenuating noise in the region above 500 Hz and amplifying noise in the regions below 500 Hz; this was done both with and without a motorcycle helmet. As our previous findings would suggest, the pattern of threshold shift is a function of the filter characteristics of the helmet, including an increased sensitivity at higher frequencies. There was also greater than expected reduction in sensitivity at frequencies where the helmet amplifies incident noise. The results indicate an acoustic effect of helmets which has not previously been reported.
Development of an advanced hearing protection evaluation system.
Authors: Shank Kevin , Oliver Josiah , Lalande Fred , Bicak Mehmet , Homma Kenji
Published: July 2011

Acoustic test fixtures (ATFs) are practical and often necessary tools for testing hearing protection devices (HPDs) especially with extremely loud impulsive and/or continuous noise, for which the use of live subjects might not be advisable. Although there have been various standardized and laboratory ATFs from past research, there still exists large uncertainty in the correlation between the attenuation results obtained from ATFs and those obtained from actual human subject tests, particularly for intraaural HPDs. It is suspected that one of the main factors contributing to the discrepancy may be insufficient fidelity in the circumaural/intraaural flesh system, whose underlying dynamics is not yet clear. Therefore the first goal of this research is to better understand this biomechanical system and implement it into a new ATF prototype which emulates circumaural/intraaural HPD attenuation performance. This prototype ATF will be validated against human subjects. This presentation discusses the research methodologies and design strategies for developing this advanced hearing protection evaluation system.
Pure-tone glide detection and simulated formant transition discrimination by listeners with hearing loss.
Authors: Nelson Peggy B. , Wojtczak Magdalena , Nie Yingjiu , Anderson Elizabeth , Davies-Venn Evelyn
Published: July 2011

Listeners with hearing loss (HI) have poorer pure-tone glide detection thresholds than normal-hearing (NH) listeners [Nelson et al., ASA Baltimore (2009)]. Many HI listeners also experience reduced masking release for glide detection in gated noise compared to their performance in steady noise. Pure tones, however, are not good representations of formant transitions in speech. In this study, we compare listeners’ thresholds for detecting pure-tone glides and for detecting changes in the spectral profile of a harmonic complex that mimics formant transitions. Formantlike transitions were simulated by adding intensity increments to harmonic components in the range 1–1.5 kHz. Increments were progressively delayed with increasing component frequency. Pure-tone glides and formantlike transitions were presented in quiet, steady noise, and gated noise to NH and HI listeners. Some but not all HI listeners showed poorer spectral profile change discrimination when compared to NH listeners, despite having normal increment-detection thresholds. A comparison of these results with pure-tone glide detection and masking release for speech will be presented. [Work supported by NIDCD Grant No. R01-DC008306.]
The effect of hearing loss on the resolution of partials and fundamental frequency discrimination.
Authors: Moore Brian C. , Glasberg Brian R.
Published: July 2011

The relationship between the ability to hear out partials in complex tones, discrimination of the fundamental frequency (F0) of complex tones, and frequency selectivity was examined for subjects with mild-to-moderate cochlear hearing loss. The ability to hear out partials was measured using a two-interval task. Each interval included a sinusoid followed by a complex tone; one complex contained a partial with the same frequency as the sinusoid, while in the other complex that partial was missing. Subjects had to indicate the interval in which the partial was present in the complex. The components in the complex were uniformly spaced on the ERBN-number scale. Performance was generally good for the two “edge” partials, but poorer for the inner partials. Performance for the latter improved with increasing spacing. F0 discrimination was measured for a bandpass-filtered complex tone containing low harmonics. The equivalent rectangular bandwidth (ERB) of the auditory filter was estimated using the notched-noise method for center frequencies of 0.5, 1, and 2 kHz. Significant correlations were found between the ability to hear out inner partials, F0 discrimination, and the ERB. The results support the idea that F0 discrimination of tones with low harmonics depends on the ability to resolve the harmonics.
Effects of frequency compression on the intelligibility and quality of speech in noise.
Authors: Souza Pamela , Arehart Kathryn H. , Kates James M. , Muralimanohar Ramesh Kumar , Croghan Naomi , Hoover Eric
Published: July 2011

Frequency-lowering technologies such as frequency compression have become common in high-end digital hearing aids. However, there are few data on the consequences of adjusting frequency compression ratio (FCR) and frequency compression cutoff (FCC). In this study, sentences at signal-to-noise ratios (SNRs) ranging from −10 to +10 dB were frequency compressed at a variety of FCRs (1.5–3) and FCCs (1–2 kHz). Frequency compression was implemented using sinusoidal modeling: the incoming signal was segmented, the spectral peaks found for each segment, and an output sinusoid at a shifted frequency was generated for each peak. Subjects were adult listeners with normal hearing or mild-moderate sensorineural loss. Intelligibility results illustrate a complex interaction between SNR and frequency compression parameters. At favorable SNRs, frequency compression had minimal effects. At less favorable SNRs, reducing FCC degraded intelligibility more than reducing FCR. At the poorest SNRs any amount of frequency compression degraded intelligibility but the specific FCC/FCR had little effect. Quality results show less interaction whereby any frequency compression was perceived as reducing speech quality. Compared to data from normal-hearing listeners, results from listeners with hearing loss were more variable and were interpretable in the context of audiogram configuration. [Work supported by NIH and GN ReSound.]
Speech intonation and perception: A study of frequency scales for Brazilian Portuguese.
Authors: Moreira Martins Marcus Vinícius , Ferreira Netto Waldemar
Published: July 2011

This work aims to verify the appropriation of the semitones scale for data analysis in studies involving intonational aspects of Brazilian Portuguese (henceforth BP), regarding mainly speakers perception and intuition at the time of production. The semitone scale was selected because it operates with frequencies ranges and with a central frequency to which the neighboring frequencies, in a given range, would be attracted covering the perception issue. The test was performed with 13 BP native speakers (seven women and six men) and consisted primarily in an exposure for a target-utterance. In next step, they were required to reproduce what they had heard: imitating just the intonation despite of the voice qualities and segments realization. The data (f0 values) obtained were plotted in mels, barks, semitones, and ERB-rates and all compared by (i) correlation (r2), (ii) variation from target-utterance values of F0, and (iii) graphics comparison. The results so far obtained and analyzed indicates that the semitones scales can be used with no loses for frequencies under 600 Hz if compared with Hz scale and better fits for heights comparison. In relation to other scales, any difference was noted in absolute values at this moment. [Work funded by CNPq, Process no. 152293/2010-8.]
Gender effects on unconscious phonetic imitation.
Authors: Black Alexis K.
Published: July 2011

Studies on unconscious phonetic imitation have examined whether participant and/or model talker gender plays a role in degree and direction of the behavior. Findings, however, have alternately demonstrated greater imitation by men, greater imitation by women, more imitation toward a male model talker, and more imitation toward opposite sex model talkers. Other studies have reported no sex-based differences in imitation. Three experiments using a blocked-shadowing paradigm assessed the role of sex on degree and direction of imitation. In the first two experiments, base rates of imitation to a single model talker of a particular sex were compared across three acoustic features: vowel quality, word durations, and voice onset time (VOT). In the third experiment participants were exposed to both male and female models. One model talker exhibited modified VOT, enabling examination of sex-based differences in imitation. Preliminary results suggest that an imitator is more likely to mimic a model talker of the opposite gender and that acoustic features are imitated to different degrees. It is suggested that different acoustic features are associated with different social categories. These differences may explain the diverse and conflicting findings on sex-based effects that have been reported in the imitation literature.
The effect of divided attention on phonetic imitation.
Authors: Abel Jennifer , Babel Molly , Black Alexis
Published: July 2011

Research suggests that phonetic imitation is an automatic and subconscious process, but it is clearly a behavior that is variable across participants and conditions. The purpose of this experiment is to explore how a participant’s level of attention to the speech signal moderates their degree of imitation. To this end, six conditions were prepared using a blocked exposure design: no redirection of attention (participants were instructed to simply listen to the model talker producing words), attention redirected through a math task, attention redirected through a picture-drawing task, attention focused through a word-memorization task, attention focused through a talker-description task, and attention focused through an explicit imitation task. A seventh condition using an immediate shadowing paradigm to compare to the blocked exposure design was run as well. Seventy native speakers of English (ten per condition) were recruited as participants. In all conditions participants’ baseline productions of the stimuli wordlist were recorded prior to exposure to the model talker (a female speaker of North American English). Recordings are currently being analyzed for imitation using various acoustic parameters including whole word duration, vowel spectra, and f0.
Prosodic and segmental conversion between speakers of different dialects.
Authors: Krivokapic Jelena
Published: July 2011

Previous work has found that speakers converge to each other’s production, as evaluated for acoustic properties of segments and in perceptual tasks [S. Fowler, J. Phonetics 25, 421–426 (1995); Pardo, J. Acoust. Soc. Am. 119, 2382–2393 (2006); Tobin, J. Acoust. Soc. Am. 125, 2757 (2009)]. Little is known about convergence on prosodic properties [L. Schweitzer, J. Acoust. Soc. Am. 128, 2458 (2010)]. An experiment is presented that examines how interaction between native speakers of British English and American English affects segmental and prosodic properties. The synchronous speech paradigm (Cummins, ARLO, 3, 7–11 (2002); Z. Cummins Proceedings of Eurospeech 2003 (2003), pp. 777–780), where two speakers read sentences at the same time, is used. Dyads consisting of one British and one American speaker read a short story that contained four words where the two dialects differ in stress pattern and ten target words where the dialects differ in vowels. The following variables are examined: vowel formant structure, vowel duration, VOT, F0 contours, stress pattern, phrasing, and pitch accent. The goal is to investigate how speakers converge to each other’s speech, and whether segmental and prosodic properties converge to the same degree. Data for dyads consisting of speakers of American English and Indian English are currently being collected.
Accent effects in auditory processing by native and non-native speakers.
Authors: Franco Kristin , Kaushanskaya Margarita
Published: July 2011

The current study examined whether non-native listeners’ perception is facilitated by a match between their L1 and the accent with which L2 words are pronounced. An auditory lexical decision task was used, where English words and nonwords were pronounced by a native speaker of English or a native speaker of Mexican Spanish. Half the words were cognates (overlapping in phonetic form and meaning across languages) while half were noncognates. Spanish-English bilinguals from Mexico and English-speaking monolinguals listened to accented and nonaccented stimuli and decided as quickly as possible whether they were English words. Results indicate an effect of lexical status and accent in both listener groups, with faster reaction times (RTs) for words than nonwords, and slower RTs on accented than nonaccented stimuli. However, English-speaking monolinguals were slower than Spanish-English bilinguals in recognizing accented English words. Moreover, Spanish-English bilinguals demonstrated faster RTs for cognates than for noncognates, but only when these were spoken with a Spanish accent. Results indicate that non-native accent influences auditory processing even in listeners who are familiar with the particular accent. Further, cognate effects indicate that lexical-phonological variables interact with acoustical factors in determining the efficiency with which the bilingual lexical system processes auditory information.
Benefits of voice gender and perceptual learning on the perception of masked speech processed through cochlear implant simulations.
Authors: Sullivan Jessica R. , Assmann Peter , Hossain Shaikat
Published: July 2011

Cochlear implant simulations were used to investigate the potential benefits of auditory perceptual training for cochlear implant users. Listeners with normal hearing attended to speech masked by a competing talker, processed through a simulation of an eight-channel cochlear implant. The aim was to determine whether perceptual training would enable listeners to benefit from differences in voice gender between target and masker. Thirty adults with normal hearing were randomly assigned to one of three training groups: matched-gender word recognition, mismatched-gender word recognition, or gender recognition. Participants completed 2 h of training within a 1-week period then returned 1 week later for a late-post testing session. Training sessions consisted of ten blocks during which the SNR (−6, 0, 6 dB) was adapted based on performance. Significant speech intelligibility improvements were observed from pre- to post-sessions for all three training groups, and these improvements were maintained at the late-post session for all three groups. Mismatched-gender word recognition training produced a larger improvement in word recognition accuracy than matched training; however, gender recognition training also yielded substantial improvement, suggesting that voice gender cues contribute to speech recognition in competing talker situations for cochlear implant listeners.
The intelligibility of Lombard speech produced and perceived in different noise conditions.
Authors: Walker Abby J.
Published: July 2011

Lombard speech is typically found to be more intelligible than speech produced in quiet when played in noise. In this study nonwords produced by 6 speakers in 4 different noise conditions (6-talker babble, and unfiltered, low-pass filtered, and high-pass filtered white Gaussian noise) were played to 100 participants in the presence of matching or mismatching noise at −5 dB signal-to-noise ratio (SNR). There were two sets of nonwords, which differed minimally in either consonant (aCa words) or vowel (shVb words). Participants were asked to identify which nonword they heard. While there was no significant effect of matching or mismatching noise conditions on intelligibility, there was a difference between the intelligibility of speech produced in harder (babble and unfiltered white noise) or easier (low and high pass noise) conditions: If speech was produced in a more difficult noise condition, that speech was more intelligible overall. Additionally, this study found that in many noise conditions, quiet speech was equally or more intelligible than Lombard speech, a finding contrary to many studies. This result is discussed in relation to methodological issues involving the relative ease of the task, and the effect of the Lombard effect on vowels versus consonants.
Does spatial release from masking interact with working memory capacity in speech perception?
Authors: Francis Alexander L. , Connell Katie , Anderson Leigh
Published: July 2011

Increasing the spatial separation of target and masking speech improves speech recognition but this benefit tends to decline with age. Previous research suggests that perceived spatial separation of targets and maskers facilitates selective attention, a mechanism that depends in part on the availability of working memory capacity. Thus, age-related loss of benefit from spatial separation may increase demands on working memory capacity for speech perception. The present study investigates the interaction between spatial separation of target and masking speech and the availability of working memory capacity, reporting results from an experiment in which listeners repeated sentences in the presence of masking speech under conditions of low- and high-working memory demands imposed via a simultaneous memory load task. Stimuli were presented from a speaker located in front of the listener with two-talker masking speech presented from one of two speakers located either 10 deg or 90 deg to one side. Preliminary results from younger adults suggest no effect of load on sentence recognition, but poorer memory task performance with 10 deg as opposed to 90 deg separation, supporting the hypothesis that spatial separation reduces working memory demand for recognizing speech in competing speech. Results from older listeners will also be discussed.
Evaluation of single- and multicarrier methods for underwater communication using data-driven simulations.
Authors: Xia Menglu , Rouseff Daniel , Ritcey James A. , Zou Xiang
Published: July 2011

Unlike in radio communications, there is no standard statistical model for the channel impulse response in underwater acoustic communications. To compare the performance of different communications strategies requires data collected under common environmental conditions. In the present paper, a data-driven simulator is developed for comparing single- and multicarrier communications algorithms. Models for the time-varying channel impulse response over a particular bandwidth are first constructed using archival experimental data. The models are then driven with novel communications sequences of lesser bandwidth. The output is synthetic received data that can then be demodulated to evaluate communications performance. By applying reciprocity to the single-input, multiple-output archival data, both multiple receive arrays and multiple transmit arrays can be simulated. Communications performance for the synthetic data is compared to actual experimental results. [Work partially supported by the ONR.]
Long-range acoustic communication in deep water with a shallow source and horizontal towed array.
Authors: Song Hee-Chun , Cho Steve , Kang Taehyuk , Hodgkiss William S. , Preston John
Published: July 2011

In September 2010 a long-range acoustic communication (LRAC10) experiment was carried out in deep water off the Southern California Coast. The experiment involved two mobile components: (1) a source towed slowly at a speed of 2–3 knots at 75-m depth and (2) a horizontal line array towed at 3.5 knots at a depth of 200-m. Phase-coherent communication sequences were transmitted in the 200–300 Hz frequency band at various ranges. Initial analysis of the LRAC10 data demonstrates that an information rate of 50 bits/s can be achieved over a 550-km range using QPSK modulation and error-correction coding combined with beamforming.
The acoustic environment of inpatient hospital wards.
Authors: Shiers N. J. , Shield B. M. , Glanville R. C.
Published: July 2011

There is an increasing body of research into the acoustic environment of hospitals, which provides evidence of the detrimental effects of noise on the well being and comfort of patients and on staff, and of a significant rise in hospital noise levels in recent years. Much of this evidence has focused on specific areas of healthcare such as critical care and operating theatres, with comparatively few studies carried out within general inpatient wards and in UK hospitals. A project is currently being undertaken to investigate, through objective and subjective surveys, the noise climate and acoustic design within general inpatient facilities in the United Kingdom, and their influence on the acoustic comfort of patients and staff. Noise and acoustic surveys have been carried out in a range of inpatient wards, with corresponding questionnaire surveys of staff and patients. Three major UK hospitals have been involved in the study, and a substantial amount of data has been collected. Reported results will include comparisons of noise levels measured in a number of ward locations including multibed and singlebed rooms, identification of the sources of high level noise, and some analysis of patient and staff attitudes to noise.
Harmonizing national & international speech privacy guidelines.
Authors: Sykes David M.
Published: July 2011

Absent leadership from the U.S. federal government, the process of developing (and continuously improving) consistent speech privacy guidelines for healthcare facilities, is like herding cats. Nevertheless, progress continues. 1 year after the release of the FGI 2010 Guidelines (and 15 years after Congress passed HIPAA) the first code-level U.S. guidelines for speech privacy, noise, and vibration in healthcare facilities were released, and several leading groups have agreed to cite the 2010 Guidelines as their sole “reference standard.” These groups are as follows: the Department of Health and Human Services (HIPAA), the Veterans Administration, the Centers for Disease Control, 38 regional authorities having jurisdiction (AHJ's), the U.S. Green Building Council’s LEED for Health Care, the Green Guide for Health Care, 48 state code authorities, and most recently, the International Green Code Council. What is left? the Joint Commission, the Department of Defense, the World Health Organization, and others. Meantime, work on the 2014 edition of the Guidelines is already underway with important updates to the speech privacy section. Since the FGI Guidelines are actively used in 16 countries, it is imperative to involve the global acoustical community in the research and development needed to strengthen them. What is the best way forward?
Acoustical modeling software as a tool to evaluate speech privacy in open plan office environments.
Authors: Newton Jessica E. , Meyer Justin E.
Published: July 2011

A productive work environment requires enough privacy to conduct confidential business on the telephone while maintaining background noise levels that allow others to concentrate on their work. However, many businesses also rely on the collaborative work environment that can be created in an open plan office. This study concentrates on using EASE computer models as a tool to demonstrate to clients and end-users what type of acoustic environment to expect when selecting different types of workstations. The degree of speech privacy afforded was tested by determining the opposite effect: the level of speech intelligibility between workstations. A typical open office layout was modeled using EASE acoustical modeling software. The speech intelligibility between workstations was modeled in several potential configurations to demonstrate the effects of the changes in speech privacy within the office. The configurations tested include varying the heights of workstation partitions and using either reflective or absorptive partition finishes.
Case study: Medical office building designed without regard for acoustical privacy.
Authors: Reuter Eric L.
Published: July 2011

A newly constructed medical office building was designed (without the aid of an acoustical consultant) such that registration, waiting, and check-out areas are closely spaced and lack architectural separation, making private verbal exchange of information impractical. A survey of patients conducted by the owner shortly after the building opened indicated that lack of oral privacy is the leading criticism of the facility. Measurements of existing privacy Index between several talker/listener position pairs demonstrate extreme deficiency relative to criteria provided by the Facilities Guidelines Institute, Green Guide for Health Care, and others. Reconfiguration would be prohibitively expensive, leaving electronic sound masking as the only practical option for improving privacy. However, the masking level that would be required to achieve adequate privacy would exceed that recommended for occupant comfort. The owner is faced with balancing the risk of litigation for breach of privacy law with the cost associated with upgrading the facility for compliance. Measured data, calculations, and an examination of the risks and benefits of various upgrade options will be presented.
Factors determining whistle emission rate in bottlenose dolphins of Bocas del Toro, Panama.
Authors: Quiñones-Lebrón S. G. , May-Collado L. J.
Published: July 2011

Dolphins of Bocas del Toro are known to change their communication signals when interacting with dolphin-watching boats. In this study we examine the role of engine noise, calf presence, and behavior on the emission rate of whistles. Whistle emission rate was measured in groups where calves were and were not present and while interacting and not interacting with boats. A general higher whistle emission rate was shown when only the research boat was present and during social events, although whistle contours were not significantly different. Whistle rate was also slightly higher in groups with calves, particularly during social events. While in the presence of other boats, whistle emissions were higher during traveling events. A low whistle emission in the presence of other boats than the research boat (largely dolphin-watching boats) may be the result of masking or a response to the engine noise during these encounters. In addition, groups with calves may be avoiding intrusive dolphin-watching boats. Most groups with calves, for which whistle emission was higher during social events, were observed during encounters with the research boat (engine off). These results provide insights on some of the environmental and biological factors that may be influencing dolphin whistle emission.
Training diving ducks for behavioral audiograms.
Authors: Therrien Sara C. , Carr Catherine E. , Dooling Robert J. , Popper Arthur N. , Therrien Ronald E. , Wells-Berlin Alicia M.
Published: July 2011

Lesser scaup (Aythya affinis) are a species of diving duck that dive to depths of greater than 20 m to forage on crustaceans, mollusks, and fish. Currently, there are no measures of underwater hearing of any diving bird because of the inherent difficulties of training a bird to respond to sound underwater. Lesser scaup in a captive colony at USGS Patuxent Wildlife Research Center in Laurel, MD are being trained to participate in in-air and underwater behavioral audiograms. Ducklings were hand-reared to respond to trainers, auditory signals, and mealworm rewards. The ducks were then trained on a go/no-go task to respond to varying frequencies and intensity levels by pecking an LED-lit target. All targets and acquisition devices were designed to follow similar procedures in-air and underwater. Previous auditory brainstem response (ABR) tests demonstrated an in-air maximum sensitivity at 2–3 kHz. These behavioral audiograms will provide a measure to compare ABR and psychoacoustic thresholds as well as a measure of underwater thresholds, which would be difficult to implement using only the ABR.
Gold-nanoparticles for optoacoustic imaging and therapy.
Authors: Frenz M. , Kitz M. , Preisser S. , Jaeger M. , Wetterwald A. , Thalmann G. N.
Published: July 2011

Gold nanoparticles have shown promise as contrast agent in optoacoustic imaging and as selective absorbers in phototherapy because of the strong surface plasmon resonance absorption at specific wavelengths. Using pressure transient detection, flash photography, two-photon luminescence microscopy, and TEM imaging, vapor bubbles generated upon irradiation of single spherical gold nanoparticles, single nanoparticles in suspension, and of nanoparticles targeted cells were investigated. Formation thresholds determined at different wavelengths indicate a bubble formation efficiency increasing with the irradiation wavelength. A value of 60 ± 5 mJ/cm2 was found for 532 nm, which is close to the wavelength of the surface plasmon resonance. The minimum threshold for acute cell damage was determined to be 54 ± 13 mJ/cm2 for a single laser pulse generating a bubble diameter of 7.6 ± 1 μm corresponding to about half of the cell diameter and 23 ± 1 mJ/cm2 for pulse train irradiation. These values have to be compared to the maximum permissible exposure limits for skin. Our results show that the particle distribution inside the cell plays a key role for the cell damage process, which strongly influences the pathways of cell targeting. A good understanding of the cell death mechanisms is a prerequisite to translate experimental findings to the clinic. [This research was supported in part by the SNF (No. 205320-116343) and the EU (No. LSHC-CT-2006-018858 PROMET.)]
Time/frequency multiple signal classification beamforming based on principle component analysis for reducing platform and flow noise and identifying continuous and impulsive ground targets on UAV.
Authors: Silva Ramon A. , Kim Yong-Joe
Published: July 2011

When a microphone array is mounted on an UAV, most existing beamforming methods cannot be used to adequately identify continuous and impulsive targets on the ground due to high-level platform and flow noise. Here, we propose to develop a time/frequency beamforming method based on a principle component analysis and multiple signal classification (MUSIC) algorithm. This method can reduce the effects of platform and flow noise, e.g., engine and boundary layer noise, by removing noise-associated principle components from measured signals. It can also pinpoint the exact target locations while most existing methods can only detect target directions. In order to validate the proposed method, a cross-shaped microphone array is installed on the bottom surface of an UAV. The UAV is then placed in a wind tunnel operating at Mach 0.05–0.1 and its engine is turned on to simulate flight cruising conditions. Two loudspeakers are used to simulate continuous and impulsive ground targets. The target locations estimated from the proposed method are compared to the actual loudspeaker locations. Through the wind tunnel experiment, it is shown that the proposed beamforming method can be used to effectively suppress platform and flow noise and successfully identify the transient targets.
Affects of nearby bubbles on underwater array gain.
Authors: Culver R. Lee , Park J. Daniel
Published: July 2011

Combining multiple sensor signals coherently (i.e., beamforming) improves spatial or angular resolution and increases signal to noise ratio (SNR). When the array is steered, signals arriving from the steering direction add in phase, while signals arriving from other directions do not (proper choice of signal frequency assumed). Array gain (AG) is a measure of how much the SNR at the array output is increased relative to array input SNR. The degradation in underwater acoustic array AG by scattering from nearby bubbles was measured at the AB Wood tank located at the Institute of Sound and Vibration Research (ISVR), University of Southampton, in June 2008. AG degradation is separate from the effects of bubbles in water to attenuate acoustic signals. Measured statistics of signal phase at the individual sensors show that as bubble density increases, phase differences between the elements increase and AG is degraded. We present a theory and numerical simulation that attributes the phase shifts to scattering from nearby bubbles and provides a way to predict AG degradation from the bubble density. [Work sponsored by the ONR Undersea Signal Processing.]
Nonlinear propagation and shock waves in histotripsy ultrasound therapy.
Authors: Maxwell Adam D. , Fowlkes J. Brian , Xu Zhen
Published: July 2011

Histotripsy is a noninvasive therapy that applies short duration, highly focused pulses of ultrasound to mechanically break down targeted tissues by acoustic cavitation. These pulses become strongly distorted due to nonlinear propagation, and shock fronts are formed at the transducer focus. Focal pressure levels at which cavitation clouds are achieved can exceed 20 MPa peak negative pressure and 100 MPa peak positive pressure. Current methods for characterizing histotripsy pulses are discussed. Single-mode and multi-mode fiber optic hydrophones have been constructed in our laboratory for measuring histotripsy waveforms. Accurate measurement of acoustic waveform shape and amplitude is important because nonlinear distortion contributes greatly to generating cavitation in histotripsy. High-speed photographic observations suggest that cavitation clouds are not formed directly by the negative pressure of the wave, but by scattering of shocks from single cavitation bubbles within the focal region. Experiments and simulations describing the role of shock waves in forming cavitation clouds during histotripsy are presented. [Work supported by NSF GRFP and NIH R01 EB008998 and S10 RR022425.]
Characterization of nonlinearly distorted ultrasound waves in water using broadband laser vibrometry.
Authors: Sapozhnikov Oleg A. , Cunitz Bryan W. , Bailey Michael R.
Published: July 2011

Laser vibrometry is a practical method to detect surface displacement. The method enables a direct measurement of acoustic field parameters such as acoustic particle displacement or acoustic particle velocity. Unlike other sensors, e.g., hydrophones, laser vibrometers are completely non-contact. Such devices are capable of measuring displacements from centimeters to sub nanometers at frequencies from near dc to 10 s of megahertz and have been proven to establish a primary standard for calibrating hydrophones [Bacon, IEEE Trans. UFFC, 35 (1988)]. In this technique, an ultrasonic transducer radiates an acoustic wave which is detected by a thin plastic membrane—a pellicle. The pellicle is effectively transparent to the acoustic beam so that the vibration of the pellicle follows the particle motion in the sound wave, but is reflective to the optical beam of the vibrometer allowing for a measurement. The present talk will report on measurements of nonlinearly distorted sawtooth waves in water performed with two commercial Polytec laser vibrometers: a scanning 24 MHz bandwidth system and a non-scanning 600 MHz bandwidth system. It is shown that appropriately chosen optical targets—pellicle or thick glass block with flat sides—allow resolution of both shock front and the smooth part of the waveform. [Work supported by NIH EB00764, NIH DK43881, and NSBRI through NASA NCC 9-58.]
Experimental characterization of shock formation distance in broadband noise propagation.
Authors: Muhlestein Michael B. , Gee Kent L.
Published: July 2011

Unlike initially sinusoidal waveforms, the definition of the “shock formation distance” for broadband noise is complicated by the fact that not all shocks form at the same rate. Examination of the concept of a “characteristic” shock formation distance for broadband noise raises some questions: Is there some generalization of the shock formation distance for sinusoidal signals or narrowband noise that can be applied to broadband noise? If so, is it inversely proportional to amplitude and frequency, as the pure tone and narrowband noise distances are? Possible methods to investigate these questions, such as statistical analyzes and examining spectral slopes and time waveform derivatives, are discussed. These techniques have been studied using experimental data acquired from finite-amplitude broadband noise propagation in an anechoically terminated plane-wave tube. Preliminary results from these experiments are discussed.