bluuebunny/crossref_metadata_2025 huggingface dataset:
Narrowband masking in birds
Authors: Brown Stacey L. , Dooling Robert J. , Leek Marjorie R.
Published: October 2013

Hearing studies show that zebra finches, Taeniopygia guttata, small song birds that produce broadband, harmonic vocalizations are unusually sensitive to the mistuning of a single component in a harmonic complex [Lohr and Dooling, J. Comput. Psychol. 112, 36–47 (1998)]. Such a change in a harmonic stimulus creates both spectral and temporal cues. Previously it has been reported that these birds have very good temporal resolution of fine detail within harmonic complexes [Dooling et al., Hear. Res. 152, 159–172 (2001)]. Here the spectral resolving power is examined by measuring auditory patterns of masking by narrowband noises. Masking patterns were measured in zebra finches using operant conditioning and the method of constant stimuli for a 100-Hz band noise masker centered at the birds frequency of best hearing, 2860 Hz. Probe frequencies were tones between 1000 Hz and 5700 Hz. Results demonstrate a symmetrical masking pattern with less upward spread of masking and a narrower resolution bandwidth in zebra finches than has been observed in humans. These findings are consistent with other measures of avian spectral resolution. [Work supported by NIH Grant DC-00198 to RJD.]
Discrimination of dynamic moving ripples in the zebra finch, Taeniopygia guttata
Authors: Osmanski Michael S. , Dooling Robert J. , Depireux Didier A.
Published: October 2013

Auditory processing of complex broadband sounds known as moving ripples has been studied both physiologically at the cortical level in mammals and psychophysically in humans [Depireux et al. (2001); Chi et al. (1999)]. These stimuli share spectro-temporal properties with many natural sounds, including species-specific vocalizations and the formant transitions of human speech [Versnel and Shamma (1998)]. One test of the generality of ripple processing beyond mammals would be to examine a non-mammalian species. Zebra finches may be excellent subjects for such a study because they produce complex broadband harmonic songs and neuronal responses in their auditory forebrain may be exquisitely tuned to the specific spectro-temporal patterns of their songs [Theunnissen and Doupe (1998)]. We trained these birds to discriminate between flat-spectrum broadband noise and moving ripples of different densities that move up or down in frequency at various rates. Results show that discrimination in zebra finches is better at those ripple densities and velocities which are prominent in their species-specific harmonic vocalizations. [Work supported by NIH Grant No. DC-00198 to RJD and NIDCD Training Grant No. DC-00046.]
Drumhead contact time measurement using metallic leaf
Authors: Sánchez José , Irwin James
Published: October 2013

This work investigates the relationship between mass, diameter, impact location, and energy of steel balls impacting upon the surface of the drumhead, and the time they remain in contact. The contact time is measured by making the ball and metallic leaf contacts in an electrical switch. The leaf was applied to the drumhead surface and connected to the circuit through a wire. The balls were connected to the circuit using a solder-attached hair-fine wire. Contact time was measured at a constant drumhead tension at three distinct locations on the drumhead: the center, halfway between the center and the rim, and an inch from the rim. In addition, a single series was measured from the center to the rim at 1/2-in. intervals. Initial work indicates that the contact time is not dependent upon energy, impact location, or diameter, but only upon the mass of the steel ball. The relationship of the mass-dependent contact time to energy transfer and to impact spectra is developed, showing mass is the determining parameter needed for the initial conditions used to simulate drumstick/drumhead interaction (impact effects).
Regimes of oscillation and reed vibrations in lingual organ pipes
Authors: Cox Eric , Rossing Thomas D.
Published: October 2013

We compare the sound generation in six lingual organ pipes including two trompette pipes, two oboes pipes, a krummhorn, and a rankett, the latter two of which were described in a previous paper [Cox and Rossing, paper 2aMU8, 142nd ASA meeting]. With the resonator attached, each pipe sounds in distinct regimes of oscillation, separated by discontinuities. The nominal frequencies of the pipes are generally slightly lower than the resonance frequency of the resonator but slightly higher than the natural frequency of the reed. The air mass loading of both the resonator and shallot lowers the reed frequency. Changing the blowing pressure has little effect on the sounding frequency but a modest effect on sound level.
Benefits and disadvantages of self-regulation of environmental noise from military training
Authors: Luz George A.
Published: October 2013

In a 1981 Executive decision, the Administration’s Office of Management and Budget (OMB) told the Environmental Protection Agency to end funding of the Office of Noise Abatement and Control (ONAC). This decision, coupled with a specific exemption for military equipment contained in the Noise Control Act of 1972, ensured that the military departments would be self-regulating in regard to noise. This self-regulation for noise stands in contrast to the external regulation of other pollutants, such as air and water emissions. Two possible disadvantages of self-regulation are (1) reduced funding for noise management compared with funding for externally regulated pollutants, and (2) lack of an independent and external set of standards for determining acceptable limits on community noise exposure. Three possible benefits are (1) avoiding the costs of mitigating trivial violations of external standards, (2) maintaining a long-standing policy of preventing noise problems through land use planning, and (3) enabling negotiated solutions between installations and their neighboring communities. The paper ends with an examination of a negotiated solution for a community subjected to noise from the detonation of obsolete ammunition.
Thin film characterization using resonant ultrasound spectroscopy
Authors: Gladden J. R. , So Jin H. , Pradhan Rajdeep , Maynard J. D.
Published: October 2013

With mechanical and electrical components approaching nanoscale dimensions, there is great interest in the properties of thin films. Some properties, such as structure and phase transitions, can be probed with measurements of elastic constants. We have been using Resonant Ultrasound Spectroscopy (RUS) to probe such properties for a variety of thin film materials including colossal magnetoresistance (CMR) materials, carbon nanotubes, and a magnetic semiconducting film on GaAs. By accurately characterizing the substrate, the elastic constants and damping of a deposited film can be determined from changes in the frequency and quality factor (Q) of the sample resonances. Issues of precision and accuracy in RUS measurements are important for application to thin films. If one is interested in relative changes in properties (e.g., resulting from temperature variations, phase transitions, etc.), the precision from sharp resonances (Q>5,000) is more than adequate. However, since a film may occupy only 1/1000 of the sample, attaining high accuracy is challenging, as uncertainty in sample dimensions and crystallographic orientation can have severe effects on results. Temperature data for the magnetic films mentioned and attenuation of carbon nanotube films will be presented. [Work supported by ONR.]
Shallow water impact acoustics
Authors: Deveau David M.
Published: October 2013

During a series of impact detection and tracking accuracy tests near Wallops Island, Maryland, an analysis was conducted on the acoustic impacts themselves. Since the impact area was very shallow (60 ft), the acoustic signature traveled unscathed between the 1000 yard baseline sensors. The initial goal was to implement deep water impact tracking algorithms in the shallow environment. Initially the in-water tracking system computed positions that were close to those which were laser sighted, but not close enough. Since the transient acoustic signature was very evident, hence a stable timing mark, an investigation into the acoustics surrounding the impact was undertaken. A review of the data showed small transients which occurred distinctly before the large transient detection that had routinely been considered as the impact itself. Using a threshold detection scheme, a relative set of timing marks were generated based on these early transients and were found to produce a more accurate placement.
Channel characterization for communications in very shallow water
Authors: McDonald Robert J. , Commander Kerry W. , Stroud John S. , Wilbur Jo Ellen , Deane Grant B.
Published: October 2013

Broadband acoustic transmissions (7 kHz to 17 kHz) taken from July 4, 2000 to July 8, 2000, in the shallow water near Scripps Pier at La Jolla, California, are used to extract the time-varying channel parameters of coherence time and multipath time delay spread, as functions of frequency and the environmental variables of wave height and tidal fluctuations. Tidal fluctuations, which have a significant effect on water depth at the receiver and transmitter, are shown to strongly correlate to variations in the multipath delay spread. Variations in the coherence time for the channel, as measured by the drop off in correlation between initial and successive impulse responses, are shown to be inversely related to variations in the measured wave height. The coherence time of the channel was found to decrease with increasing center frequency. A scatter plot of the receiver signal-to-noise ratio as a function of wave height and water depth indicates when the shallow water environment allows a viable communications channel to exist.
Multipath in synthetic aperture sonar
Authors: Piper John E.
Published: October 2013

Synthetic aperture sonar is capable of producing high resolution images. As the detection range increases multipath effects can become important. In this paper we present the results of at-sea tests in the Gulf of Mexico and St. Andrew Bay with a dual-frequency (20 kHz and 180 kHz) synthetic aperture sonar. Surprisingly, it was found that range to water depth ratios as small as 4 often produced multipath signals significantly stronger than direct path signals. These effects on the synthetic aperture processing and image quality are discussed.
Spherical wave approximation to arbitrary sound fields
Authors: Rayess Nassif E.
Published: October 2013

The ability to expand the acoustic field radiated from arbitrarily shaped objects in the form of a series of spherical wave functions has always been a point of interest. Despite the paucity of theoretical understanding, experimental and numerical work has repeatedly shown that such expansions can lead to relatively accurate approximations of the radiated sound fields. A general understanding of the problem as well as a quantitative approximation of the resulting errors are deduced from the sound radiation model based on a volume distribution of monopole sources. The errors involved in the approximation are a direct result of the presence of monopole sources outside the largest inscribed sphere. It is shown that under many circumstances, such errors are relatively small and can be mitigated further by the proper choice of the method used to determine the coefficients of the expansion. The collocation method with an appropriate sampling scheme has been used with a great deal of success to determine the expansion coefficients in acoustic holography problems.
Engineering challenges of the acoustics of a political convention
Authors: Randorff Jack E.
Published: October 2013

The acoustical challenges encountered during the 2000 Republican Convention are discussed. The convention has held in Philadelphia, Pennsylvania’s First Union Center. This venue is a dual-purpose facility catering to professional basketball and professional ice hockey. The acoustical needs of the delegates and the broadcast audience are discussed. The technical performance requirements of convention sound reinforcement and media network broadcast feed are outlined. The necessary technical and performance trade-offs are enumerated with respect to the physical constraints, schedule requirements, budget limitations, and technical planning committee expectations. The conversion of a major sporting arena to a large-scale meeting room with reverberation times and general room conditions conducive to good listening was a significant undertaking. The site had been chosen for a preliminary screening visit approximately 2 years before. This presentation is a followup to ‘‘Acoustics of Political Conventions—A Review,’’ delivered at the Acoustical Society of America 139th Meeting in Atlanta in June 2000, 2 months before the convention in Philadelphia.
Experimental studies of the interaction of ultrasound with bone: What have we learned in 50 years?
Authors: Nicholson Patrick
Published: October 2013

Despite five decades of study, our knowledge of the interaction of ultrasound with bone remains incomplete. On the one hand, ultrasound propagation in cortical bone is relatively well-understood. Given its low porosity, cortical bone can be treated as a homogeneous anisotropic solid for the purposes of low-MHz ultrasound assessment. Consequently, ultrasound velocity measurements have been used very successfully as an in vitro tool to determine elastic constants. Developing useful clinical techniques for cortical bone assessment has been more difficult, although approaches such as critical angle reflectometry look promising. Understanding ultrasound propagation in trabecular bone, a highly porous fluid-saturated solid with a complicated microarchitecture, has proved a tougher problem. A wide range of clinical devices are already in use despite the fact that, with some notable exceptions, there have been few rigorous attempts to probe the underlying physics. This situation is being resolved, with recent studies into the validity of Biots and Schoenbergs theories for porous and stratified media, respectively, and also work looking at the role of scattering and the value of backscatter measurements. The insights emerging from this new phase of research are likely to trigger a new generation of acoustic techniques for bone characterization.
Continuous mapping of the acoustic properties of biological materials with emphasis on bone
Authors: Lees Sidney
Published: October 2013

Instruments determine the time of flight through a prepared section of bone of uniform thickness. A multigated receiver can be set to capture successive pulse echoes. A clock turned on by the first pulse echo is turned off by the next. A faster driven transducer maps the bone section. Several tissue properties can be calculated from the time of flight, the amplitude, thickness of the bone section and its density. In particular, the variation of the elastic properties provides a detailed picture of stress distribution on the bone. Several examples will be shown.
Comparison of machine and human recognition of isolated instrument tones
Authors: Fujinaga Ichiro
Published: October 2013

This paper describes three different machine recognition experiments and a recently conducted human experiment in order to compare the abilities of machines and humans to recognize isolated instrument tones. The computer recognition software is based on the Lazy Learning Machine, which is an exemplar-based learning system using a k-nearest neighbor (k-NN) classifier with a genetic algorithm to find the optimal set of weights for the features to improve its performance. The performance of the software was progressively improved by adding more features. These include centroid and other higher order moments, such as skewness and kurtosis, the velocities of moments, spectral irregularity, tristimulus, and time–domain envelope shape. Also, realtime recognition is now possible by using Miller Pucketts PD, a realtime software synthesis system, and his fiddle∼ object. The training data was taken from the McGill Master Samples. The human experiment involved eighty-eight conservatory students. Although the average human scores are similar to the machine scores, the best human subjects far exceeded the capabilities of the machine. The excellent performance of the humans in this experiment presents new challenges for timbre-recognition computer models.
Wet wall thermoacoustics in a single pore
Authors: Espino Brian , Wilen Larry
Published: October 2013

We will discuss thermoacoustic measurements in a single circular pore with a mixture of air and methanol vapor as the working gas. The vapor is in coexistence with liquid methanol capillary-condensed in a thin porous material lining the inside wall of the pore. From measurements with no temperature gradient, the diffuso-acoustic function F(λD) may be obtained. At low frequencies, condensation/evaporation and vapor diffusion is rapid enough to maintain the methanol partial pressure constant at its saturated equilibrium value. At high frequencies, the methanol partial pressure undergoes adiabatic pressure oscillations along with the air. F(λD) describes the transition between these behaviors. λD = √2R/δD, where δD is the penetration depth for binary diffusion. The measurements probe a range of λD from about 1 to 10. With an applied temperature gradient, thermoacoustic effects due to condensation/evaporation combined with vapor transport are detected. Results will be compared to recent theoretical predictions for wet wall thermoacoustic effects [Slaton et al., J. Acoust. Soc. Am. 105, 65–73 (1999) and references cited within]. [Work supported by ONR.]
Nonlinear acoustic techniques for landmine detection: Experiments and theory, Part II
Authors: Korman Murray S. , Sabatier James M.
Published: October 2013

A nonlinear acoustic technique for detecting buried landmines has been suggested by Donskoy [SPIE Proc. 3392, 211 (1998); 3710, 239 (1999)] and verified in a number of experiments by Sabatier et al. [J. Acoust. Soc. Am. 110, 2757, 2758 (2001)]. Airborne sound involving two primary frequencies f1 and f2 undergo acoustic-to-seismic coupling which interacts with the compliant mine and soil to generate a difference frequency component that can effect the vibration velocity at the surface. An LDV profile across a buried mine at the difference frequency (chosen at a resonance) showed more relative sensitivity than a linear profile. A layer of soil in a large tube, terminated by an airbacked clamped thin elastic plate, is used to model nonlinear effects including Donskoy’s ‘‘bouncing’’ soil–mine interface. The frequency spectrum of modes of the plate’s response is investigated vs the amount of soil mass loading. In particular, the lowest mode frequency first decreases with loading and then increases. Linear response curves near resonance compare well with the difference frequency response as one primary is varied. [Work supported by the United States Army Communications-Electronics Command Night Vision and Electronic Sensors Directorate.]
Effect of reverberation on speech intelligibility in young children
Authors: Litovsky Ruth
Published: October 2013

Children spend a majority of their time in noisy and reverberant environments, where a listener’s abilities to understand speech and localize its source are compromised. The present study utilizes a novel test, which was developed in our lab for the purpose of assessing the ability of young children to understand speech in the presence of competing sources, and the extent to which they benefit from spatial separation between target speech and competitors. A 4AFC identification procedure was used, with (familiar) words from the Spondee List for targets. Testing was conducted in three rooms with different spatial dimensions and acoustic characteristics (reverberation times T60 equal to 250 ms, 500 ms, and 1200 ms). The target was always presented from the front. Conditions were: quiet, with competing sounds near the target, or with competing sounds 90° away from the target. Data were collected from children with normal hearing, ages 4–7 years. Results suggest that, while children benefit from spatial separation of target and competitors, this benefit becomes increasingly smaller as the amount of reverberation in the room increases. This finding may be relevant in our efforts to improve room acoustics and enhance children’s ability to learn in classrooms.
On sound generation mechanism by a centrifugal blower
Authors: Wu Sean
Published: October 2013

Centrifugal blower noise has often been modeled as dipoles and quadrupoles to account for the effects of fluid–structure interaction and turbulence as the impeller rotates. However, many experimental results have shown that sound powers from centrifugal blowers increase with speed to the power of 4–6, which implies the existence of a monopole [Lighthill, Proc. R. Soc., Ser. A 222, 564–587 (1952)]. This paper demonstrates that such a monopole indeed exists for a blower running inside a heating ventilation and air-conditioning (HVAC) unit of a vehicle. Tests indicate that this monopole is producible by a volumetric fluctuation due to an unsteady rotor. When the blower is operated at the voltage power input specified by the car manufacturer, the sound power increases with the speed to the power of 4. When the blower is installed on a stable shaft and running at the same voltage power input, the volumetric fluctuations are significantly reduced and the sound power increases with speed to the power of 6. This implies that the monopole sound has been effectively replaced by the dipole sound. Since dipole is less effective in generating sound at low speeds than monopole, eliminating rotor fluctuations can lower vehicle HVAC noise levels.
Optimal sweep cycle for time-varying comb filters for binaural dichotic presentation to improve speech perception in sensorineural hearing impairment
Authors: Cheeran Alice N. , Pandey Prem C. , Jangamashetti Dakshayani S.
Published: October 2013

In a previous investigation [P. C. Pandey et al., J. Acoust. Soc. Am. 110, 2705 (2001)], a scheme using binaural dichotic presentation was devised for simultaneously reducing the effect of increased temporal and spectral masking in bilateral sensorineural hearing impairment. Speech was processed by a pair of time-varying comb filters with passbands corresponding to cyclically swept auditory critical bands, with the objective that spectral components in neighboring critical bands do not mask each other and sweeping of filter passbands provides relaxation time to the sensory cells on the basilar membrane. Presently investigation is carried out to find the optimal value of the sweep cycle. Comb filters used were 256-coefficient linear phase filters, with transition crossovers adjusted for low perceived spectral distortion, 1 dB passband ripple, 30 dB stopband attenuation, and 78–117 Hz transition width. Acoustic stimuli consisted of swept sine wave and running speech from a male and a female speaker. Bilateral loss was simulated by adding broadband noise with constant short-time SNR. Listening tests with stimuli processed using sweep cycles of 10, 20, 40, 50, 60, 80, 100 ms indicated highest perceptual quality ranking for sweep cycle in the 40–60 ms range, with a peak at 50 ms.
Preliminary observations of infants’ detection of backward masked tones
Authors: Werner Lynne A. , Parrish Heather K.
Published: October 2013

Backward masked thresholds appear to have a prolonged developmental course compared to other measures of auditory capacity, but backward masking has not been studied in infant listeners. The present study examined 7–9-month-old infants’ detection of 20-ms, 1-kHz pure tones masked by a 50-ms, 2.5-kHz-lowpass noise. The interval between the offset of the tone and the onset of the masker was 0 ms. Both stimuli had 5-ms rise and fall times. The spectrum level of the masker was 30-dB SPL. Thresholds for the backward masked tone were determined adaptively for 6 young adults using a rule that converges on the 71% correct point on the psychometric function. The average threshold was 50-dB SPL (SD=12 dB). Thirteen infants were trained to respond to a backward masked 95-dB SPL tone, but not to the masker alone. These infants then completed 30 single-interval test trials, with 15 no-signal trials and 15 signal trials with the tone fixed at 85-dB SPL and the same backward masker. Infants achieved a p(C)max of about 0.7 (SD=0.05) in this task. These results suggest that at this age infants’ backward masked threshold is about 35 dB higher than the adults’.
Role of auditory feedback in speech produced by cochlear implanted adults and children
Authors: Bharadwaj Sneha V. , Tobey Emily A. , Assmann Peter F. , Katz William F.
Published: October 2013

A prominent theory of speech production proposes that speech segments are largely controlled by reference to an internal model, with minimal reliance on auditory feedback. This theory also maintains that suprasegmental aspects of speech are directly regulated by auditory feedback. Accordingly, if a talker is briefly deprived of auditory feedback speech segments should not be affected, but suprasegmental properties should show significant change. To test this prediction, comparisons were made between speech samples obtained from cochlear implant users who repeated words under two conditions (1) implant device turned ON, and (2) implant switched OFF immediately before the repetition of each word. To determine whether producing unfamiliar speech requires greater reliance on auditory feedback than producing familiar speech, English and French words were elicited from English-speaking subjects. Subjects were congenitally deaf children (n=4) and adventitiously deafened adults (n=4). Vowel fundamental frequency and formant frequencies, vowel and syllable durations, and fricative spectral moments were analyzed. Preliminary data only partially confirm the predictions, in that both segmental and suprasegmental aspects of speech were significantly modified in the absence of auditory feedback. Modifications were greater for French compared to English words, suggesting greater reliance on auditory feedback for unfamiliar words. [Work supported by NIDCD.]
Speech feature discrimination in deaf children following cochlear implantation
Authors: Bergeson Tonya R. , Pisoni David B. , Kirk Karen Iler
Published: October 2013

Speech feature discrimination is a fundamental perceptual skill that is often assumed to underlie word recognition and sentence comprehension performance. To investigate the development of speech feature discrimination in deaf children with cochlear implants, we conducted a retrospective analysis of results from the Minimal Pairs Test (Robbins et al., 1988) selected from patients enrolled in a longitudinal study of speech perception and language development. The MP test uses a 2AFC procedure in which children hear a word and select one of two pictures (bat–pat). All 43 children were prelingually deafened, received a cochlear implant before 6 years of age or between ages 6 and 9, and used either oral or total communication. Children were tested once every 6 months to 1 year for 7 years; not all children were tested at each interval. By 2 years postimplant, the majority of these children achieved near-ceiling levels of discrimination performance for vowel height, vowel place, and consonant manner. Most of the children also achieved plateaus but did not reach ceiling performance for consonant place and voicing. The relationship between speech feature discrimination, spoken word recognition, and sentence comprehension will be discussed. [Work supported by NIH/NIDCD Research Grant No. R01DC00064 and NIH/NIDCD Training Grant No. T32DC00012.]
Cochlear-implant simulations of speech in complex acoustic backgrounds
Authors: Qin Michael K. , Oxenham Andrew J.
Published: October 2013

Cochlear-implant simulations have shown that good speech intelligibility in quiet can be obtained with very poor spectral resolution and no temporal fine-structure information. It is not known how robust speech is to such processing in the presence of complex interfering sounds. This study examined speech reception for sentences in the presence of four types of interference (broadband noise, broadband noise modulated with a speech envelope, a single male talker, and a single female talker) and three processing schemes (24- and 8-channel cochlear-implant simulations and unprocessed). The spectral resolution in the 24-channel condition was designed to be comparable to that of normal hearing, but the original temporal fine structure was replaced by noise in both the 24- and 8-channel processing conditions. Performance with 24-channel processing was substantially poorer than in unprocessed conditions, despite the relatively good frequency resolution. Eight-channel processing produced the poorest performance. Stimulus processing was generally more detrimental to speech reception in the fluctuating interferers than in the unmodulated noise. The detrimental effects of eliminating fine-structure information may be due to the reduction in pitch cues, which listeners may use to help segregate the sources. [Work supported by NIDCD Grant R01DC05216.]
Typicality ratings of male and female voices
Authors: Spisak Brian , Mullennix John , Moro Kelly , Will Jessica , Farnsworth Lynn
Published: October 2013

Researchers have suggested that human voices are represented in memory in terms of prototypes [e.g., Kreiman and Papcun (1991); Papcun et al. (1989)]. Others have suggested that speech utterances are stored in memory via detailed exemplar-based representations [e.g., Lachs et al. (2000)]. The goal of the present study was to provide the first step toward assessing the viability of a prototype view of voice. Ten hVd utterances were recorded from each of 20 male and 20 female speakers. The utterances were blocked by speaker gender and presented to male and female listeners who rated each stimulus on a 1–7 typicality scale from ‘‘least typical voice’’ to ‘‘most typical voice.’’ There were significant effects of the type of vowel and speaker voice on the ratings, as well as interactions of vowel type with gender of subject and speaker voice. The results are discussed in terms of the strength of evidence for a graded category structure of voice categories that would be consistent with a prototype perspective of long-term memory representations of voice.
Study of effect of low-pass filtering for channels amplitude estimation on speech intelligibility by acoustic simulation of SPEAK strategy
Authors: Dashtseren Erdenebat , Kitazawa Shigeyoshi
Published: October 2013

The conventional way of amplitude envelope estimation for stimulation pulse train generation for selected channels within multi-channel cochlear implant speech processors is low-pass filtering of half or full wave rectified (HWR or FWR) frequency bands of the corresponding channels. To study the necessity of low-pass filtering (LPF) for amplitude envelope generation, acoustic simulation of the SPEAK speech strategy was implemented. Stimulation pulse patterns for selected channels are estimated without LPF and compared to those estimated by the conventional way. Acoustic stimuli are regenerated using an overlap adding technique of filtered pulse trains. Speech intelligibility tests on CV and VCV of Japanese within normal-hearing subjects were conducted to measure the effect of LPF. A one-way ANOVA indicates that the LPF with a cutoff frequency 160 Hz for amplitude envelope estimation of selected channels negatively affected the speech intelligibility.
Further investigations on binaural intelligibility of reverberant speech
Authors: Libbey Brad , Rogers Peter
Published: October 2013

There is a binaural intelligibility advantage for many subjects when listening to reverberant speech. Two processes offer explanations as to why the binaural advantage exists. First, directional information may identify echoes and remove a portion of the reverberation in a manner similar to the precedence effect. A more likely possibility is that the reverberation behaves as additive noise with a specific time and frequency dependence. In this case, subjects may utilize the coherence of the left and right channels to limit the effects of the incoherent reverberation, similar to binaural masking release. To test the latter hypothesis, subjects listen to diotic (L+R), binaural (L&R), and diotic (L or R) reverberant words. The diotic treatment (L+R) adds two recordings measured at the location of the listener’s ears. Since the listener faces the source, the direct signals are coherent while some cancellation is expected for the reverberation. The presentation will compare diotic (L+R) intelligibility to the binaural (L&R) condition as well as the diotic (L or R) control condition where the left or right signal plays to both ears.
The perception of voice pitch by naïve and experienced listeners
Authors: Fucci Donald , Schueller Marianne , Bond Zinny
Published: October 2013

Perceptual judgments of a single speaker’s voice pitch will be characterized by any given listener along a subjective continuum. Individual listener attributes have been suggested as an explanation for this diversity in categorizing voice pitch. Professionals involved in the evaluation of voice, specifically voice pitch, are expected to possess a level of perceptual skill that reliably quantifies pitch regardless of personal attributes. Two groups of individuals, one naïve and one experienced, were asked to perceptually match voice pitch during two pitch matching tasks. The first task involved matching an audio taped voice pitch produced on the vowel /a/ to a musical note on a keyboard. The second task involved listening to an audio-taped voice producing words, then matching the voice pitch of the word to a musical note on a keyboard. Accuracy of perceptual judgments was measured upon stimuli produced and assigned musical keyboard note by master’s level opera music majors. Results indicate that a difference exists between groups in only one of the four variables measured. Individual differences varied, but appeared unrelated to previous musical experience.
Peripheral and central locus of a nonspeech phonetic context effect
Authors: Sullivan Sarah C. , Lotto Andrew J.
Published: October 2013

Previous work has demonstrated that nonspeech sounds with the appropriate spectral characteristics can affect the identification of speech sounds [Lotto and Kluender, Percept. Psychophys. 60, 602–619 (1998)]. It has been proposed that these spectral context effects are due to interactions in the peripheral auditory system. For example, they could be the result of masking at the auditory nerve or of auditory enhancement effects that have been demonstrated to be monaural [Summerfield and Assmann, Percept. Psychophys. 45, 529–536 (1989)]. To examine the locus of the context effect, synthesized syllables varying from /da/ to /ga/ were preceded by single-formant stimuli that mimicked the third formant of the syllables /al/ and /ar/. The nonspeech stimulus was presented either to the same or opposite ear as the target speech stimulus. Subjects speech identifications were shifted as a function of context in predicted directions for both presentation conditions. However, the size of the shift was smaller when the context was in the ear contralateral to the target syllable. These results agree well with similar results for speech contexts. The data suggest that the context effects occur at multiple levels of the auditory system and are not simply examples of masking or auditory enhancement.
Effects of bandpass noise and telephonic filtering on the perception of consonants
Authors: Purnell Thomas , Kopplin Laura
Published: October 2013

Consonant identification studies report varying results of the usefulness of information above 4 kHz. A recent study found listeners misidentifying female-produced consonants characterized by a center of gravity above 3.5 kHz [P. G. Stelmachowicz et al., J. Acoust. Soc. Am. 110, 2183–2190 (2000)], suggesting that the perception of alveolar stops and fricatives as spoken by females are misperceived in common environments which filter out high-frequency spectral information. In the current study, consonant identification of female tokens consisting of consonants varying by place or manner ([ptk], [fTsStS], [ttSsSnlr]) was tested in a forced choice experiment. Tokens were low-pass filtered at 3.5 kHz simulating telephonic filtering. Additionally, the locus of spectral information below 4 kHz was assessed by comparing responses to tokens masked by nonmodulating noise, where the signal-to-noise ratio was at least 10 dB SPL. Noise masking occurred between 0 and 0.4, 0.4 and 2, and 2 and 3.5 kHz. Confusion matrices indicated that the perception of unmasked speech is not hindered by low-pass filtering at 3.5 kHz, while perception of masked tokens was worse with masking between 2 and 3.5 kHz.
Center-of-gravity effects in the perception of high front vowels
Authors: Jacewicz Ewa , Feth Lawrence L.
Published: October 2013

When two formant peaks are close in frequency, changing their amplitude ratio can shift the perceived vowel quality. This center-of-gravity effect (COG) was studied particularly in back vowels whose F1 and F2 are close in frequency. Chistovich and Lublinskaja (1979) show that the effect occurs when the frequency separation between the formants does not exceed 3.5 bark. The COG and critical distance effects were manifested when a two-formant reference signal was matched by a single-formant target of variable frequency. This study investigates whether the COG effect extends to closely spaced higher formants as in English /i/ and /I/. In /i/, the frequency separation between F2, F3, and F4 does not exceed 3.5 bark, suggesting the existence of one COG which may affect all three closely spaced formants (F2=2030, F3=2970, F4=3400 Hz). In /I/, each of the F2-F3 and F3-F4 separations is less than 3.5 bark but the F2-F4 separation exceeds the critical distance, indicating two COGs (F2=1780, F3=2578, F4=3400  Hz). We examine the COG effects using matching of four-formant reference signals, in which we change the amplitude ratios, by two-formant targets with variable frequency of F2. The double-staircase adaptive procedure is used. [Work supported by an INRS award from NIH to R. Fox.]
Effects of reverberation on spatial auditory performance and spatial auditory cues
Authors: Shinn-Cunningham Barbara , Kopčo Norbert
Published: October 2013

Ordinary room echoes and reverberation influence sound localization performance, moderately degrading judgments of source direction (i.e., judgments of azimuth and elevation) while vastly improving judgments of source distance. The relative magnitude of the influence of room acoustics on localization performance depends on the location of the listener in a room; specifically, performance is best when the listener is far from any wall (when there are no early, intense echoes). However, in addition to depending on listener location, localization performance in all three spatial dimensions depends on past experience in a particular room and improves over time. This room learning (which is not seen in a comparable anechoic study) at least partially generalizes across listener positions in a room. After reviewing results of localization studies demonstrating these effects, acoustic analyses are presented that show how echoes and reverberation alter and distort the spatial acoustic cues reaching the listener in an ordinary room and how these distortions vary with listener location in the room. Possible mechanisms to explain how spatial auditory processing might adapt in different acoustic environments in order to improve localization accuracy will be discussed. [Work supported in part by AFOSR Grant F49620-01-1-0005 and the Alfred P. Sloan Foundation.]
Speech intelligibility prediction of room with curved surfaces by means of its physical characteristics
Authors: Harun Mokhtar , Rahman Tharek Abdul , Ibrahim Md. Najib , Jaafar Md. Yunus
Published: October 2013

In the room, it was found previously that the ear uses the first arriving sound to locate the source, but the early reflections contribute to the intelligibility. Late reflections, on the other hand reduce intelligibility. Therefore, for speech intelligibility a high sound energy fraction is necessary, requiring high early energy and low late energy. Spatial impression which is the subjective effect of early sound reflections that come from the side walls and ceiling, contributes to the sense of envelopment. This paper presents the investigation of speech intelligibility with respect to the physical characteristics of rooms with curved surfaces. The investigated physical characteristics are source-to-listener distance (Lr), listener-to-the farthest wall (Lwmax), listener-to-the closest wall (Lwmin), listener-to-the farthest wall and listener-to-the average distance to walls (Lwave). In addition to objective acoustics measures such as reverberation time (RT60), early decay time (EDT), average sound absorption coefficient (Aave) and clarity (C50), speech intelligibility predictors STI and Alcons were also measured and analyzed. It is the intention of this paper to explore the possibility of predicting speech intelligibility performance of a room with curved surfaces by using its physical characteristics.
Surface response of a viscoelastic medium to subsurface acoustic sources with application to medical diagnosis
Authors: Yazicioglu Yigit , Royston Thomas J. , Loth Francis
Published: October 2013

The response at the surface of an isotropic viscoelastic halfspace to buried fundamental acoustic sources is studied theoretically, computationally and experimentally. Finite and infinitesimal monopole and dipole sources are considered. Analytical and numerical integral solutions that account for compression, shear and surface wave response to the buried sources are formulated and compared with numerical finite element simulations and experimental studies on finite dimension phantom models. The focus here is on developing a better understanding of how biological soft tissue affects the transmission of vibro-acoustic energy from biological acoustic sources below the skin surface, such as a turbulent regime in an artery caused by a partial blockage. Such an understanding could catalyze the development of noninvasive procedures using an array of acoustic sensors on the skin surface for the identification and monitoring of vascular blockages a precursor to many serious cardiovascular diseases. [Research supported by NIH NCRR Grant ♯14250 and the Whitaker Foundation.]
A USAE frequency shift method for monitoring stiffness variations in tissues
Authors: Konofagou Elisa , Hynynen Kullervo , Thierman Jonathan
Published: October 2013

In solid mechanics, the resonance frequency of a material is typically linked to its mechanical properties. A frequency shift therefore typically denotes a change in stiffness. It has already been shown that temperature variation causes stiffness changes in tissues. The amplitude of the ultrasound-stimulated acoustic emission (USAE) signal has also been shown to vary with temperature as well as indicate temperature elevation. Its amplitude, however, is sensitive to both acoustical and mechanical parameters, which at most frequencies have opposite effects resulting from temperature changes. In this paper, the measurement of a frequency shift of the USAE resonant peaks is used for monitoring of the tissue stiffness variation with temperature. In a numerical simulation, the variation of the frequency shift (ranging between −150 and 500 Hz) at different temperatures is shown. Then, in a series of experiments involving a gel phantom and porcine muscle tissue, the frequency shift variation (ranging between −200 and 200 Hz) is shown to follow the known stiffness changes due to temperature. Both simulation and experimental results indicate that the USAE frequency shift method can dissociate the mechanical from the acoustical parameter dependence and detect tissue coagulation. [Work supported by NIH Grant CA82275.]
Underwater acoustic intensity measurements using a pressure/particle-acceleration intensity vector sensor
Authors: Kim Kang , Lauchle Gerald C. , Gabrielson Thomas B.
Published: October 2013

The acoustic field of simple sources is investigated by measuring the simultaneous, colocated acoustic pressure and particle acceleration with a neutrally buoyant underwater acoustic intensity vector sensor. This sensor consists of a piezoceramic hollow-cylinder pressure transducer, and a pair of miniature accelerometers mounted inside of the cylinder. A free-field calibration is performed under the ice of a flooded quarry, while in a laboratory test tank, the 2-D acoustic intensity field is mapped for various acoustic source configurations. These include a single spherical source and a pair of spherical sources that vibrate in or out of phase with each other. A sinusoidal signal of various frequencies between 2 and 20 kHz is gated in all of these experiments in order to suppress the effects of environmental reflections. The receiving beam pattern of the intensity sensor is also measured and reported. An analytical model for the interaction of two closely spaced spherical radiators is developed, and predictions from it compare well with the measured intensity field. Some limitations in the experiments, and future work are discussed. [Work supported by ONR, Code 321SS.]
The design, fabrication, and acoustic calibration of a 1-3 piezoelectric polymer composite-based cylindrical array module for towed applications
Authors: Benjamin Kim C. , Szelag Jeffrey A.
Published: October 2013

A cylindrical transducer array module containing eight double-layered 1–3 piezocomposite elements was acoustically calibrated in the frequency range 10–100 kHz. Each wedge-shaped element, covering approximately one octant (45) of the cylindrical radiating aperture, was housed in a molded syntactic foam hub component with its outer surface conforming to a cylindrical aperture 12.7 mm in diameter. The construction approach described would allow one to connect several modules of similar (or varying) diameter along the axial direction for towed-array applications requiring directional transmit and receive performance. The double-layer element design provides two independent electrical control points for optimizing the spatial and spectral response in both transmit and receive modes. The cylindrical module fabrication approach, associated tooling, and measured acoustic results for a single module under various drive conditions will be presented to illustrate the utility of this new transducer technology. [Work sponsored by the U.S. Navy.]
An analytical application of a time-reversal mirror in a sensor with solid cylindrical waveguides
Authors: Puckett Anthony D. , Peterson M. L.
Published: October 2013

A solid cylindrical waveguide or buffer rod is commonly used to isolate piezoelectric transducers from high temperature and pressure. Due to constraints on the waveguide dimensions, multiple longitudinal modes are often propagated. Dispersion and the existence of the multiple modes make it difficult to perform standard ultrasonic measurements. To simplify the measurements an analytical model was developed to model the dispersion in the multimode waveguide. This model was used to calculate the time-reversed signal required to reconstruct a pulse in the waveguide. The time-reversed signal was used in experiments to demonstrate the ability of the calculated time-reversed signal to construct a pulse. The experiments also showed the ability of the analytical model to represent the dispersion in the waveguide. Results are presented and the limitations of the analytical model presented are discussed. [Research sponsored by the Ballistic Missile Defense Organization through the ONR, Science Officer Dr. Y. D. S. Rajapakse.]