bluuebunny/crossref_metadata_2025 huggingface dataset:
They are your ears: Personal protection and personal responsibility.
Authors: Murphy William J.
Published: July 2011

Hearing protection devices are a primary means of protecting workers from occupational noise-induced hearing loss. However, the Achilles’ heel of this approach is the correct and consistent use of personal protective equipment. When workers fail to wear or fit protection correctly, they risk compromising their hearing. Currently five companies have developed commercial fit-testing solutions for hearing protection devices that can be used in a range of acoustical environments. In some cases the fit-test method requires a quiet test space because hearing thresholds are measured for unoccluded and occluded conditions under headphones. In other cases, the measurements are conducted above threshold and can be performed in acoustical environments with more background noise. These solutions will be presented along with evidence of how training in protector use can affect self-efficacy and attitudes toward using protection. Pending changes in the US Environmental Protection Agency regulations for labeling a variety of hearing protection will be discussed. Example cases for estimating occupational noise exposure with the new labels will be presented.
Statistical assessment behind a standard on hearing protector field attenuation measurement devices.
Authors: Voix Jérémie , Murphy William J.
Published: July 2011

New measurement systems for assessing individual hearing protection device (HPD) performance in the field have been developed over the past several years to address the question of what amount of protection is a given individual getting from an HPD. Although these systems, referred to as field attenuation measurement systems (FAMSs), have the same purpose and produce attenuation values that are presented in similar ways, the underlying technology used to produce a personal attenuation rating (PAR) can be drastically different, ranging from psychophysical tests to objective microphone measurements and involving single or multiple frequency measurements. In an effort to ensure that FAMS provide an attenuation rating that is a both a scientifically valid number and a meaningful reading for the end-user, the members of the American National Standard Institute Working Group 11 have recently been starting to work on a proposed standard to specify the minimum performance criteria for a FAMS to assure it provides data with defined accuracy and precision. The current paper describes the underlying statistical assessments that are considered in the standard. Specifically, the computational details of the number of subjects required for various assessments made within the standard for the determination of the maximum permissible background noise, measurement uncertainty, and HPD fit uncertainty will be presented. The paper will also detail the calculation of the repeatability and reproducibility.
Measurement of impulse peak insertion loss for five hearing protectors.
Authors: Murphy William J. , Flamme Gregory A. , Khan Amir , Echt Joseph , Johnson Belinda C.
Published: July 2011

In 2009, the US Environmental Protection Agency proposed an impulse noise reduction rating (NRR) for hearing protection devices. The impulse NRR is based the American National Standard, ANSI S12.42-2010, and requires measurements with an acoustic test fixture for three ranges of impulse noises: 130–134, 148–152, and 166–170 dB peak SPL. Five protectors of each of five models (The Combat Arms Linear, Combat Arms Nonlinear, EAR Pod Express, Etymotic EB1, and Bilsom 707 Impact II, all in passive mode) were evaluated per the levels specified in the ANSI standard. Impulses were generated by an acoustic shock tube in the laboratory and by a 0.223 caliber rifle in the field. At each peak impulse level, protector samples were fitted on the test fixture five times and for each insertion, at least three impulses were measured. The impulse NRR increased with peak pressure and ranged between 20 and 38 dB. For some protectors, significant differences were observed across protector examples of the same model and across insertions. Relationships between the continuous noise NRR, the impulse NRR, and the increase in allowable impulse exposures due to the protector will also be presented.
Hearing conservation in high school students: A model using significant threshold shifts.
Authors: Martens Dave , Dunn Aericka , Freeman Katherine , White Shanna , Yonovitz Al
Published: July 2011

Hearing loss affects 19.5% of adolescents between 15 and 19 years [Shargorodsky et al. (2010)]. Although often subtle, this hearing deficit impairs perception of speech and warning signals and may increase the risk of depression, accidents, and social isolation. It is now commonly known that even slight hearing loss (15–24 dB) can create a need for speech and language therapy and auditory training with specialized equipment. In adults, the leading preventable cause of acquired sensorineural hearing loss is exposure to excessive levels of noise, however, concern has now reached a pinnacle that children and young adults are developing noise induced hearing loss as a result of overexposure to amplified music, especially through the use of personal music players. Three high schools (N>3000) are now part of a study that (1) provides threshold audiograms on each student, (2) determines a threshold shift between a baseline and annual audiogram, and (3) provides intensity measures of personal music devices and education to students. This program and its implementation will be discussed.
Acoustical characterization of exploding hydrogen-oxygen balloons.
Authors: Vernon Julia A. , Gee Kent L. , Macedone Jeffrey H.
Published: July 2011

Exploding balloons are popular demonstrations in introductory chemistry and physical science classes and as part of outreach programs. Anechoic measurements of various hydrogen and hydrogen-oxygen balloons were made using 3.18 and 6.35 mm microphones placed at various angles and distances from the balloon. Time waveform data from each explosion were collected at a sampling frequency of 192 kHz. Initial research, presented previously, was conducted to determine potential auditory hazard as a result of exposure to these balloons. Further analysis has been conducted on the explosions’ time waveforms and calculated spectra to characterize hydrogen-oxygen balloons as an impulsive noise source. Consideration is given to level, waveform A duration, rise time, angular variation, and repeatability. Comparisons with other impulsive noise sources are also presented.
The experimental measurement of motorcycle noise.
Authors: Carley Michael , Kennedy John , Walker Ian , Holt Nigel
Published: July 2011

The noise source mechanisms involved in motorcycling include various aerodynamic sources and engine noise. The problem of noise source identification requires extensive data acquisition of a type and level that have not previously been applied. Data acquisition on-track and on-road are problematic due to rider safety constraints and the portability of appropriate instrumentation. One way to address this problem is the use data from wind tunnel tests. The validity of these measurements for noise source identification must first be demonstrated. In order to achieve this extensive wind tunnel, tests have been conducted and compared with the results from on-track measurements. Sound pressure levels as a function of speed were compared between on-track and wind tunnel tests and were found to be comparable. Spectral conditioning techniques were applied to separate engine and wind-tunnel noise from aerodynamic noise and showed that the aerodynamic components were equivalent in both cases. The spectral conditioning of on-track data showed that the contribution of engine noise to the overall noise is function of speed and is more significant than had previously been thought. These procedures form a basis for accurate experimental measurements of motorcycle noise.
Spectral filtering characteristics of a motorcycle helmet.
Authors: Walker Ian , Holt Nigel , Kennedy John , Carley Michael
Published: July 2011

Noise transmission characteristics of a motorcycle helmet have been analyzed using a combination of insertion loss measurements and loudness matching in a behavioral study. Results demonstrate the action of the motorcycle helmet as a spectral filter. The insertion loss measurements confirm previously published data showing attenuation in the frequency range above 500 Hz. A further feature, the significance of which is addressed and highlighted here for the first time, is an amplification of noise below 500 Hz. In short, the helmet acts as a frequency dependent filter on the input to the human auditory system. Data from the matching task were used to generate equiloudness curves which show the effect of the helmet on riders’ perceptions of loudness. The generated curves were compared to the international standards (ISO226). The character of the equal loudness curves was strongly influenced by the helmet. This difference is discussed in the framework of the filtering characteristics of the helmet.
Acoustic properties of natural gas hydrates and the geophysical assessment of the subsurface distribution of hydrates in the Gulf of Mexico and Atlantic.
Authors: Shedd William , Frye Matt , Godfriaux Paul , Kramer Kody
Published: July 2011

Natural gas hydrates are a solid form of natural gas found in the deep water marine margins of continents and under permafrost in Arctic regions worldwide. They have been recognized as a very significant potential energy source in the future. They form under high pressure and low temperature. Hydrate saturated sediments are acoustically faster and slightly less dense than water saturated sediments, but much faster and denser than gas saturated sediments. These properties allow for the identification of marine hydrate saturated sediments that are underlain by gas saturated sediments. The resulting geophysical reflector, referred to as a bottom simulating reflector, or BSR, often mimics the seafloor in areas where geothermal gradient is laterally consistent. The Bureau of Ocean Energy Management, Regulation, and Enforcement has used three-dimensional seismic data in the Gulf of Mexico and two-dimensional seismic data in the Atlantic to (1) map the distribution of BSRs, (2) drill six wells in the GOM with moderate to high hydrate saturations in sand reservoirs, and (3) assess the resource potential of hydrates.
Acoustic studies of submarine gas hydrates on the Cascadia Margin.
Authors: Zykov Mikhail M. , Chapman N. Ross
Published: July 2011

Submarine gas hydrates were detected over large areas in the Cascadia margin off the west coast of British Columbia by the presence of bottom simulating reflectors in seismic surveys. Initial estimates of gas quantity based on these data and results from an ocean drilling program leg were highly optimistic, and subsequently many different experiments were carried out to quantify the estimates. This paper presents results from an air gun survey with ocean bottom seismometers deployed around a hydrated cold vent to determine the hydrate concentration in the vicinity of the vent. Reflection travel time data from the survey were used in a linearized inversion to determine the velocity structure within the hydrate stability zone. Reflection amplitude data were analyzed to generate maps of the reflectivity at the sea floor and at the base of the stability zone. The travel time inversion revealed that the sediment velocities were very low, indicating low concentration of hydrate (less than 2% of sediment volume) in the stability zone. The sea floor reflection amplitude data provided a map showing an elliptical extent of the sea floor vent. Inversion of amplitude data from the BSR indicated a small decrease in velocity, less than 7%.
Elastic constants of palladium hydride at elevated temperature and pressure.
Authors: Adebisi Rasheed , Gladden Joseph
Published: July 2011

Hydrogen atoms occupy the octahedral interstitial sites provided by metals with fcc lattices (such as palladium). Palladium hydride (PdHx) exists in two phases. At room temperature, the low concentration (PdHx=0.02) called α-phase has slightly larger lattice parameter compared to that of pure palladium. Above this concentration and up to (PdHx=0.6) the high concentration β-phase appears resulting in (α+β)-phase, a mixed phase region, and the lattice parameter becomes substantially greater than that of pure palladium. When x>0.6, α-phase disappears and the system becomes purely β-phase. The three phases coexist at the tri-critical point (temperature, pressure, and concentration). Resonant ultrasound spectroscopy (RUS) has been used to investigate the elastic constants of palladium hydride crystal and the equilibrium dynamics of the system around the tri-critical point temperature and pressure. A large decrease in shear modulus is noticed near this tri-critical point. The desire to have fundamental understanding of metal-hydrogen systems and to explore this for possible technological applications has been the motivation for research of these systems. This investigation includes the design and construction of high temperature and high pressure RUS cell.
Heartbeat-synchronous audiometry.
Authors: Hartmann William M. , Cho Yun Jin
Published: July 2011

The goal of heartbeat-synchronous audiometry (HSA) is to measure the effect of a listener’s heartbeat on pure-tone detection thresholds. Our experiment used 100-ms tones (20-ms rise/fall) with onsets occurring at selected phases of the heartbeat cycle. Cardiac waves were acquired with three chest electrodes at a sample rate of 2400 sps. Successive peaks of the QRS complex (ventricular depolarization), sharpened with a software Schmitt trigger, served to identify heartbeat cycles. The arrival time for the next heartbeat was predicted using a weighted moving-average online computation with special compensation for early beats. Software optimization led to measured rms prediction errors averaging 0.04 (sd=0.01) cycles. The HSA technique was applied to one-interval (Békésy tracking) and two-interval (up-down staircase) audiometric methods. Reproducible 4-kHz threshold maxima (cardiac-phase=0.3 cycles) and minima (cardiac-phase=0.7 cycles) differing by more than 6 dB were seen for a listener with pulsatile tinnitus. For normal listeners, interest centers on the frequencies of emissions or deep valleys in the audiogram. [Work supported by the NIDCD Grant No. 00181.]
Effects of repeated measures on the late auditory evoked response.
Authors: Goshorn Edward L. , Marx Charles G. , Simmons Alaina
Published: July 2011

A concern in clinical applications of the late auditory evoked response is the variability of amplitude and latency. While there is agreement that less variability is seen within than across subjects, the effects of stimulus and acquisition factors are not fully understood. This project examined the effects of repeated measures and stimulus type [1 kHz tone at 40 and 80 ms and speech (da) at 40 ms] on the amplitude and latency of P1. Latency was measured conventionally while amplitude was measured in two ways: peak-to-baseline (P-B) and peak-to-trough (P-T). Two amplitude measures were obtained because some commercially available instruments provide a P-B measure as the default amplitude. Stimuli were presented to 30 normal hearing young adults at 60 dBnHL. P1 latency increased significantly (p=0.024) from replicate 1 (35.9 ms) to replicate 3 (41.1 ms) for the 40 ms tone but not for 80 ms nor for speech. P-B amplitudes were significantly (p<0.01) smaller than P-T. Also, P-T amplitudes diminished significantly (p<0.01) from replicate 1 to replicate 3 for each stimulus type but P-B amplitudes did not. These findings suggest that P-B and P-T are not identical measures of P1 physiological activity.
Relationship between channel interaction and spectral-ripple discrimination in cochlear implant users.
Authors: Jones Gary L. , Drennan Ward R. , Rubinstein Jay T.
Published: July 2011

Many cochlear implant (CI) users achieve remarkable success in understanding speech, but a key limitation affecting CI development is poor understanding of factors that contribute to individual performance. The spectral-ripple discrimination test offers a time-efficient, nonlinguistic measure that is correlated with perception of speech and music by CI users. What makes this test time-efficient, and thus clinically relevant, is that it is a “one-point” measure: Only the ripple density parameter is varied. However, there is controversy within the CI field about what this one-point test actually measures. The current work examines and models the relationship between thresholds in the spectral-ripple test, in which stimuli are presented acoustically, and interaction indices measured under the controlled conditions afforded by a research processor. Preliminary results show that (1) within individual subjects, there can be large variations in the interaction indexp; (2) interaction indices generally decrease with increasing electrode separation; (3) ripple discrimination thresholds increase with decreasing mean interaction index; and (4) trends in ripple thresholds predicted by a phenomenological model are consistent with psychophysical results. Results are consistent with the use of cross-channel cues by CI users in spectral-ripple discrimination. [Research supported by NIH-NIDCD Grant Nos. F32-DC011431, R01-DC007525, P30-DC04661, and L30-DC008490 and the Advanced Bionics Corporation.]
Speech and music recognition with acoustic simulations of a harmonic single sideband encoding strategy for cochlear implants.
Authors: Li Xing , Nie Kaibao , Imennov Nikita , Won Jong Ho , Atlas Les , Rubinstein Jay
Published: July 2011

Cochlear implant users experience difficulties in speech perception in noise and music perception. Previous studies suggested that these difficulties are partially due to the lack of temporal fine structure (TFS) coding in cochlear implants [Moore, JARO (2008)]. TFSs are generally high-frequency signals; therefore, delivering perceivable TFS cues in electrical hearing is a challenge because the temporal sensitivity in cochlear implants is typically restricted to 300 Hz and below. A recently-proposed strategy, harmonic single sideband encoder (HSSE), could potentially use the harmonic structure of sounds to coherently demodulate TFS information [Li et al., ICASSP (2010)]. To evaluate these potential benefits to speech and music perception, this study compared the performance of five normal hearing listeners using four- and eight-channel sinusoidal vocoder simulations of HSSE and the continuous interleaved stimulation (CIS) strategy. Scores on the following tasks were measured: sentence recognition in noise and single-talker maskers, melody and timbre recognition, and Mandarin tone discrimination. In all of the tasks, HSSE listeners obtained a significant performance improvement over the CIS vocoder. Furthermore, simulation results from an electrically-stimulated model of the auditory nerve fibers demonstrated that HSSE is capable of encoding temporal pitch cues better than CIS. [This study was supported by NIH R01-DC007525, P30-DC004661, and T32-DC005361; AFOSR Grant FA9550061019; CGF 657635; ITHS 620491; Advanced Bionics Graduate Fellowship; and NSF TG-IBN090004.]
Implicit and explicit phonetic imitations in single-word shadowing.
Authors: Babel Molly , Delaney Meaghan , Savji Soraya
Published: July 2011

Talkers spontaneously accommodate to a model talker in single word shadowing tasks. This behavior has been termed implicit phonetic imitation, as talkers have no awareness of having modified their speech. In this study, we compare implicit phonetic imitation to explicit phonetic imitation across two groups of participants. All participants completed an auditory naming task, which included 50 monosyllabic words with the vowels /i ae a o u/ produced by a male model talker. With the exception of task instructions, the procedure was identical for both groups; one group, however, was given the instruction to explicitly imitate the model talker, while the other group was simply instructed to repeat the words naturally. We compare imitation across the two groups both acoustically by measuring vowel spectra and final stop patterns and auditorily by having listeners judge perceptual similarity. The results indicate (1) explicit and implicit imitation target different aspects of vowels; (2) the release of final stops are imitated in both conditions, but to a greater extent in the explicit condition; and (3) listeners perceive imitation in both conditions, but, again, to a greater extent in the explicit condition.
Accommodation to sinewave speech is an online effect.
Authors: Hillenbrand James M. , Clark Michael J.
Published: July 2011

In earlier work [Hillenbrand et al., J. Acoust. Soc. Am., 124, 2435 (2008)], we reported poor intelligibility (53.5%) for sinewave replicas of vowels in /hVd/ syllables. Tests with a separate group of listeners showed substantially higher intelligibility (73.1%) when the same syllables were preceded by a brief sinewave carrier phrase (CP). Additional tests showed the following: (1) a CP enhancement effect was seen even when the talkers used to generate the CP and the /hVd/ syllables did not match, showing that listeners are accommodating to the sinewave speech patterns and not solely to the talkers, and (2) a natural speech CP produced a decrease in intelligibility, showing again that listeners are accommodating in some way to the unusual characteristics of sinewave speech. In the present study, listeners identified sinewave /hVd/ syllables either alone or preceded by the sinewave CP in alternating blocks of trials (i.e., sinewave /hVd/ syllables alone and /hVd/ syllables preceded by a sinewave CP). Results using this alternating-block format showed that enhancement due to the CP comes and goes as the CP comes and goes. This finding suggests that the effect is an online or real-time effect. [Work supported by NIH.]
Adaptive learning response to auditory perturbation of voice quality feedback.
Authors: Urberg-Carlson Kari , Munson Benjamin , Watson Peter
Published: July 2011

Adaptive learning of speech behavior has been demonstrated in the areas of vowel height and backness [Houde (1998); Guenther (2006)] and pitch [Larson (1998)]. In each of these studies, the acoustic feedback presented to a speaker was perturbed, and most speakers modified their speech behavior to compensate. Adaptive learning is distinguished from feedback control if the compensatory behavior persists briefly once the perturbation is removed. The aim of the current study is to examine compensatory vocal behavior when voice quality is artificially perturbed. The common voice disorder, muscle tension dysphonia (MTD), in which a patient is hoarse in the absence of any physiological impairments, may be triggered by this type of compensatory behavior such as adaptation during an upper-respiratory infection. In this experiment, the perceived breathiness of speakers without vocal pathology will be artificially increased by mixing speech-shaped noise into the vocal feedback presented to the speaker. In pilot data with one speaker, when noise was added, spectral slant (H2-H1) increased. The increase in spectral slant indicates an increase in the closed phase of phonation, compensating for the perceived breathiness. Implications of these data will be discussed relative to the onset and maintenance of MTD.
Prosody transfer in second language acquisition: Mandarin Chinese tonal alignment in English pitch accent.
Authors: Kim Miran , Lu Yu-an
Published: July 2011

Tonal alignment patterns of Mandarin Chinese (L1) in production of English pitch accent are investigated in this study. Previous studies have observed that the F0 of lexical tone in Mandarin is closely aligned with the carrier syllable. This study examines whether this stability in the lexical tonal alignment is transferred to L2 prosody production, such as pitch accent in English. The F0 contours of native speakers of Chinese were analyzed for the English listing contour (L*+H) and a sequence of lexical tones (low-rise) at varying speech rates. Regardless of the distinct prosodic structures between Chinese lexical tone and English pitch accent, our results indicate that the native tonal alignment pattern can influence L2 production, in which the listing contours produced by Chinese speakers are systematically associated with syllable edges. This tonal alignment pattern was consistent across variable speech rates; each tonal target was associated with a syllable edge. On the other hand, the tonal alignment in the English speakers’ listing contour was not as stable as the Chinese pattern. The results suggest that Chinese speakers seem to reinterpret the pitch accent (L*+H) similar to lexical tone sequences (e.g., L-R), and transfer their native pattern to the production of L2 prosody.
Long term average spectrum predicts accent normalization.
Authors: Huang Jingyuan , Holt Lori , Lotto Andrew
Published: July 2011

Several studies have manipulated the accent of a spoken passage, observing shifts in subsequent speech perception. Such “accent normalization” may be related to remapping phonetic space or, alternatively, to tuning auditory representations via context. In the current experiments, artificial “accents” with precisely specified acoustic vowel distributions isolated the influence of these two potential mechanisms. Participants were exposed to a spoken passage drawn from Dr. Seuss’ The Foot Book with /i/ shifted to /I/ (higher-F1), or /U/ shifted to /u/ (lower-F1), or with both manipulations and then categorized /i/-/I/ or /U/-/u/ series. The third context had shifted phonetic categories, but little change in the context’s long term average spectrum (LTAS), known to influence subsequent speech categorization. As expected, higher-F1 contexts led to more low-F1 (/i/, /u/) target responses whereas lower-F1 contexts predicted more high-F1 targets (/I/, /U/) responses. However, we did not observe shifted vowel categorization after the context with little LTAS change (/i/ and /U/ shifted in opposing directions). Thus, although lexical information suggested shifted phonetic categories in this condition, there was no accent normalization. General auditory mechanisms sensitive to LTAS may play an important role in what has been thought to be accent-dependent remapping of phonetic space.
Musical training affects the representation of speech.
Authors: Jantzen McNeel G. , Aamodt Dane , Stratton Zachary
Published: July 2011

Musicians are more sensitive to acoustic features such as onset timing and frequency [Levitin (2006)]. Musical training may enhance the processing of acoustic information for speech sounds. The following questions were addressed to determine how musical training enhanced ability to perceive and represent a single speech sound in the presence of multiple sounds: (1) Does musical training improve performance on a dichotic listening test? (2) How does musical training affect the ability to attend to auditory streams? (3) How does the neural representation of the speech signal compare to behavioral results for musicians and nonmusicians? (4) Do musicians show more bilateral and/or right hemispheric activity when perceiving speech sounds. 30 subjects, 15 musicians, and 15 nonmusicians were presented with a voiced unaspirated stop consonant in one ear and a voiceless unaspirated consonant in the other ear such that all combinations were presented. Through five tasks, subjects identified a dominant speech sound, indicated location for a specified speech sound, and indicated speech sound for a specified location. Behavioral results indicate that musical training improved subjects’ ability to perceive specified speech sounds. Musical training effects and organization of acoustic features were reflected in the EEG as observed by location and amplitude of the ERPs.
Training listeners to report fundamental frequency and formant range information independently.
Authors: Barreda Santiago , Nearey Terrance M.
Published: July 2011

The vowels of speakers of different sizes vary in terms of their average f0 and formant frequencies. In general, larger speakers produce vowels with lower formant frequencies and lower f0s. Listeners have demonstrated the ability to estimate the approximate size of a speaker and previous experiments have shown that these judgments are based on the joint consideration of f0 and formant range information. Thus both lower f0s and lower formant frequency ranges are associated with larger speakers by listeners. Studies which have asked listeners to evaluate voices have focused on the extraction of apparent speaker characteristics (which are informed by f0 and formant frequencies) rather than asking speakers to report f0 and formant range information directly. The current study consists of a training procedure by which participants will learn to report the f0 and formant range of voices independently. The training consists of a voice matching game in which participants hear a pair of vowels produced by a voice and are asked to indicate which of the candidate voices they just heard. Results will be analyzed in light of current theories of vowel perception and normalization.
Intelligibility of dual narrow passbands with mismatched bandwidths: Anomalous findings and their rules.
Authors: Warren Richard M. , Bashford James A. , Lenz Peter W.
Published: July 2011

Unlike paired 1-octave bands, intelligibility of paired 1/3-octave speech bands can exhibit extreme hyperadditivity when heard together. Thus, for everyday sentences, the intelligibilies of 1/3-octave (4 semitones) rectangular speech bands centered at 1 and 3 kHz were 14% and 6%, respectively; when heard together intelligibility was 75%. In experiment 1, each of these bands in turn was chosen as the pedestal and remained fixed at 4 semitones and was paired with bandwidths of the second band at 3, 2, 1, or 0.5 semitones. Intelligibilities for each pairing were the same regardless of which band served as the pedestal despite the difference in the constituent intelligibilities. For example, the intelligibility of paired bands consisting of a 4 semitone pedestal and a 2 semitone variable (total bandwidth of 6 semitones) was 60% regardless of which band served as pedestal. In experiment 2, the same total bandwidth of 6 semitones was produced by setting the bandwidths of each of the bands at 3 semitones: Once again the intelligibility was 60%. Additional experiments have supported these novel findings concerning the intelligibility of paired speech bands. Implications will be discussed including the relevance for cochlear implant design. [Work supported by NIH.]
Effects of spectral degradation on contextually driven shifts in phonetic categorization.
Authors: Rhone Ariane E. , Winn Matthew B.
Published: July 2011

Under conditions of spectral degradation, listeners have been shown to experience deficits in perception of some consonant and vowel contrasts that are driven by spectral cues. In everyday listening situations, cues to phonetic contrasts are dynamic, owing to varying listening contexts both across- and within-talkers. This adds an added layer of spectral information not typically captured in assessment of cochlear implant users or normal-hearing listeners in simulated conditions. A series of experiments was designed to assess the ability of these listeners to use spectral cues to normalize and adjust phonetic boundaries across talkers and across various phonetic contexts. These tasks involved the adjustment of the alveolar/palatal fricative boundary, which has previously been shown to be sensitive to talker gender as well as vowel context. Preliminary results suggest that when spectral resolution is degraded, listeners show an impaired ability to adjust to these contexts. It is also suggested that visual information can substantially mitigate these deficits, at least for the phonetic contrasts tested here. These results help to explain some of the difficulties experienced by cochlear implant users in common conversational settings, and reinforce the importance of compensatory strategies (such as audio-visual integration) to aid in perception.
Bluefin12 buried mine identification system.
Authors: Holtzapple Richard
Published: July 2011

The Bluefin12 buried mine identification system, developed under the sponsorship of the Office of Naval Research (ONR) as a close range target reacquire and identify system, is based on the 12.75-in. unmanned underwater vehicle (UUV) developed by Bluefin Robotics. This system is integrated with a multi-sensor package that consists of the buried object scanning sonar (BOSS) system, a passive multi-axis real-time tracking gradiometer and an electro-optic sensor. The BOSS system is a downward looking sonar system that uses a broad-band, low-frequency omni-directional acoustic projector, and 20-element hydrophone receive arrays embedded in each of two 1-m length wings. The BOSS provides detection and classification of not only proud but also partially and fully buried targets. Beam forming and synthetic aperture processing generates multi-aspect three-dimensional imagery consisting of X-Y (top), X-Z (front), and Y-Z (side) perspective views providing target dimension and orientation and where the X-Z and Y-Z views provide target burial depth information. This paper presents a brief history of the development and integration of the BOSS system on the Bluefin12 UUV and specific results obtained during field surveys and system demonstration tests held in Panama City, FL and other sites.
In situ learning techniques for underwater object classification.
Authors: Rabenold Patrick , Li Hui , Carin Lawrence
Published: July 2011

A Bayesian in situ learning framework is presented that integrates several techniques to dynamically learn and adapt to variable sensing environments and the resulting manifestations of objects of interest. Sensing data are often collected from an environment for which little or no a prior knowledge is available. The presented framework exploits the contextual information of unlabeled data by learning a semi-supervised classifier on the complete data manifold. An active learning component augments limited labeled data through the adaptive selection of unlabeled samples that, given acquired labels, minimize uncertainty in the classifier. Both myopic and nonmyopic active learning methods are presented, where nonmyopic selection of the most-informative subset of samples is an extension of the myopic approach and leverages properties of submodular set functions. Additionally, the framework addresses the problem of imperfect acquired labels by accounting for uncertainty in a label within the classifier design. The benefits of the in situ learning techniques are demonstrated through the application to underwater object recognition. [This work was supported by the Office of Naval Research.]
Differential frequency hopping performance in Doppler-inducing underwater acoustic communication channels.
Authors: Cazzanti Luca , Das Arindam K. , Egnor Dianne E. , Edelson Geoffrey S.
Published: July 2011

The relationships between the parameters of Doppler spread-inducing underwater environments and the bit-error performance of differential frequency hopping (DFH) modulation in the underwater acoustic channel are characterized. Wind speed determines the nature of the effect that the water surface imposes on the acoustic DFH wavefoms propagating underwater. Low wind speeds result in an essentially flat, low-absorption sea surface. In this regime, strong surface reflections and little frequency spreading make intersymbol interference (ISI) the dominant effect on the received waveforms. At high wind speeds, the higher density of air bubbles in the surface layer absorbs almost all energy incident on the surface, resulting in no surface reflections reaching the receiver. In this regime, the surface has little effect on the received signal, either in the form of ISI or frequency spreading. The intermediate ranges of wind speed, with a mix of ISI and surface-induced Doppler spread, pose the most challenging conditions. Simulations and at-sea experiments show that recent algorithmic improvements to the receiver make DFH robust to a variety of environmental conditions and that DFH modulation parameters can be easily adapted to a variety of operationally relevant scenarios based on environmental information.
The simulation research on the underwater communication system based on the vector hydrophone.
Authors: Zhang Guangpu
Published: July 2011

In this paperC the vector hydrophone is applied to the OFDM underwater acoustic communication system. The directivity of vector hydrophone is used to shield the strong interference. The method has obvious effect on enhancing the anti-isotropic-interference, improving SNR, and reducing bit error rate. The result of simulation indicates that the OFDM communication system based on the vector hydrophone is the effective solution scheme for achieving the high speed underwater acoustic communication.
Case study: Innovative techniques for improving speech privacy in open plan offices.
Authors: Brooks Bennett M.
Published: July 2011

An acoustical engineering study was conducted to develop renovations to improve the speech privacy in an open plan office. The existing open plan configuration was to be maintained in this renovation, constraining the design effort. Therefore, several innovative designs were added to more traditional techniques. Articulation index (AI) test data, measured both before and after the renovation installation, were used to assess the improvements in speech privacy between several areas in the subject office space. The renovations included the installation of absorbent panels on the ceiling and walls, partition toppers for the conference rooms, aerogel banners, door seals, and a sound masking system. Measured speech privacy was significantly increased in the renovated office areas.
Enhancing targeted focused ultrasound therapy using light, sound, and nanoparticles.
Authors: Roy Ronald A. , McLaughlan James R. , Murray Todd W.
Published: July 2011

The use of targeted nanoparticles for both imaging and therapeutic applications shows significant promise. Photoacoustic tomography is a non-invasive imaging technique based on the detection of broad-band acoustic emissions generated by the absorption of laser light in tissue. The introduction of light-absorbing gold nanoparticles can improve signal emission levels and, if functionalized, can promote the targeting of specific cell populations, thereby enhancing both contrast and the ability to delineate tissue types. For a sufficiently high laser fluence, a transient vapor cavity is formed which collapses inertially, generating a broadband emission and even greater contrast enhancement. However, the fluence required typically exceeds the maximum permissible exposure for tissue. By combining ultrasonic and optical pulses, the light and sound thresholds required to repeatedly generate inertial cavitation (IC) can be significantly reduced, thus reducing both the laser fluence and acoustic pressures required to generate images from these acoustic emissions. The presence of IC in continuous wave high intensity focused ultrasound (HIFU) exposures can locally enhance the heating resulting in effective tissue ablation at lower HIFU intensities. [Work supported by a Boston University COE Dean’s Catalyst Award and the Gordon Center for Subsurface Sensing and Imaging Systems (NSF ERC Award No. EEC-9986821).]
Acousto-optic sensitivity mapping of biological tissues under insonification by high-intensity focused ultrasound.
Authors: Powell Samuel , Leung Terence S.
Published: July 2011

By means of the acousto-optic effect, a focused acoustic field may perturb the optical paths within a particular region of a highly scattering medium. These perturbations cause the modulation of a speckle pattern formed when multiple optical paths from a coherent source interfere at a detector position. Through analysis of this modulation, the contrast of biological tissues at near-infrared wavelengths can be exploited to determine the optical properties of biological tissue with a spatial resolution comparable to the dimension of the acoustic focus. It has been demonstrated ex vivo that this technique is capable of monitoring changes in the optical properties of biological tissue in the acoustic focus region during treatments using high-intensity focused ultrasound. The sensitivity of this approach to the optical properties of regions external to the focus has not yet been examined; this is a key question in determining the clinical viability of this approach. This work presents modulation depth sensitivity maps in various clinically relevant geometries with varying background and target optical properties and high intensity, non-linear acoustic field distributions. The sensitivity maps are generated using a novel Monte-Carlo simulation code which is accelerated by highly parallel execution on graphics processing units.
Subsampled array design for compressive sensing.
Authors: Gaumond Charles F. , Edelmann Geoffrey F.
Published: July 2011

Optimal array design is considered for beamforming using the compressive sensing technique. Compressive sensing is an l1 technique suitable for solving inverse problems that are highly undersampled and would be considered ill-posed by conventional l2 methods. Consequently, fewer array elements are required to successfully detect targets and suppress sidelobes and noise. An array does not need to be spaced at half-wavelength intervals, nor are the beams required to be orthonormal. In fact, compressive sampling works best when sample points are at apparently random intervals (satisfying the uniform uncertainty principle). This paper considers conventional, subsampled, random, logarithmic, and Golomb spaced arrays for the purpose of target detection via compressive sensing. [Work supported by the ONR.]
Measurements of spark-generated N-waves in air using a combination of acoustical and optical methods.
Authors: Blanc-Benon Philippe , Yuldashev Petr V. , Ollivier Sbastien , Averiyanov Mikhail V. , Sapozhnikov Oleg , Khokhlova Vera A.
Published: July 2011

Accurate measurement of broadband acoustic signals in air, particularly N-waves, remains a challenge. Bandwidth of existing microphones typically does not exceed 150 kHz, which results in significant overestimations of the shock rise time. To better resolve the shock thickness, it is proposed to use a focused optical shadowgraphy technique. The approach is tested experimentally. A spark source is used to generate high amplitude N-waves in air. Acoustic measurements are performed using conventional microphones (3 mm diameter), and optical shadowgrams are made using a collimated light beam from a 20-ns flash source. The results of modeling based on the generalized Burgers equation are in a good agreement with the microphone measurements in respect to the wave peak pressure and duration. However, the measured rise time of the front shock is ten times longer than the calculated one, which is attributed to the limited bandwidth of the microphone. The recorded optical shadowgrams in the vicinity of the shock front are compared with shadow patterns predicted theoretically. It is shown that a combination of microphone measurements and focused optical shadowgraphy is a reliable way of studying evolution of spark-generated shock waves in air. [Work supported by RFBR, French Government, and CNRS PICS 5603.]
Airborne shocks: Measurement methods and challenges.
Authors: Gabrielson Thomas B.
Published: July 2011

While most nonlinear phenomena are intriguing, the nature and behavior of acoustic shocks are particularly captivating. Rather ordinary sources can produce traveling wave fronts with pressure rises approaching 1% of atmospheric pressure on microsecond time scales. The resulting pressure signature can be challenging to record accurately; such measurements often require special sensors and always require an understanding of the influence of the sensor on the pressure field. Without careful design, such a measurement can become a characterization of the microphone itself with little information about the shock. There are a number of techniques for correcting the aberrations introduced by measurement microphones and a number of approaches to constructing special sensors. This presentation will summarize a subset of these techniques primarily in the context of measurement of weak shocks—shocks that travel at approximately the ordinary speed of sound but that have rise times from 10 μs down to a few tenths of a microsecond.
Acoustical filters and nonlinear acoustic wave propagation in liquids.
Authors: Pantea Cristian , Sinha Dipen N.
Published: July 2011

Generation of nonlinear acoustic waves of low frequency, less than 100 kHz, with associated low beam spread has potential imaging applications in highly absorptive media as encountered in the downhole geothermal and oil exploration environment. One of the particular advantages of the nonlinear acoustics approach of wave generation is the narrow beam spread of the difference frequency component. The difference frequency beam spread is determined by the beam profile of the primary high-frequency components used in the nonlinear mixing process. In the present study, we investigate the influence of acoustical filters in the beam path on the propagation of the generated difference frequency beam. Primary frequencies of approximately 1 MHz are used, resulting in a difference frequency component of around 100 kHz. Our results show that the difference frequency beam maintains its collimation even after passing through different acoustical filters where the primary frequencies are blocked and there is no more frequency mixing of the primaries. However, the amplitude of the difference frequency component starts decaying in an exponential fashion as predicted.
English and Russian listeners perceive cues to lexical pitch accent differently.
Authors: Shport Irina A. , Guion-Anderson Susan
Published: July 2011

This study examines the difference in perception of the fundamental acoustic cue to Japanese lexical pitch-accent—a sharp F0 fall following the F0 maximum—by native listeners of two stress languages, English and Russian. In both languages, F0 fall is not a cue to stress, but intonational high-low pitch accents exist. Previous work showed that English listeners were sensitive to the F0 fall in a discrimination task; however, they did not use the F0 fall information in a pitch pattern categorization task [Shport and Guion-Anderson, J. Acoust. Soc. Am. 127, 2024 (2010)]. Similar results were expected for native Russian listeners. Preliminary data suggest that Russian and English listeners differ in their perception of Japanese pitch patterns. Russian listeners are slightly less sensitive to the F0 fall in a discrimination task than English listeners; however, they appear to employ this acoustic cue for pattern categorization. Specifically, patterns without the F0 fall tend to be perceived as having a prominent first syllable as compared to patterns with the F0 fall. This response tendency is the reverse of Japanese listeners. The difference between English and Russian listeners is discussed in terms of native-language prosody shaping the perception of foreign-language prosody.