bluuebunny/crossref_metadata_2025 huggingface dataset:
Acetylcholine effects on tone elicited single unit responses in rat auditory cortex
Authors: Rucker H. K.
Published: October 2005

Urethane (1.5 g/kg) anesthetized male Sprague-Dawley albino rats were affixed with a head bolt and a burr hole placed over the temporal cortex and wound edges infiltrated with lidocaine before being placed in an electrically shielded, sound attenuating chamber. Tone bursts were generated with a software controlled M308 stimulus generator and 300 stimulus control module (Modular Instruments, Inc.) and sent via a secondary amplifier to a Realistic 40-1377 loudspeaker. Sound-pressure levels were determined with a calibrated 14-in. B & K 4135 condensor microphone. Single unit activity was recorded via the center barrel (4M NaCl) of glass multi-pipette. Drug barrels contained acetylcholine chloride (0.5M, pH 4.5), atropine sulfate (0.02M, pH 5.0), and glutamic acid (monosodium salt, 0.2M, pH 8.0). Sixty-six percent (n = 21) of units characterized demonstrated an atropine sensitive Ach facilitated response to near best frequency tone bursts. An atropine insensitive Ach induced response decline was noted in 13% (n = 4). [Work supported by NSF Grant BNS 8617937.]
Anomalous degradation of electromechanical coupling and resonance frequency in tonpilz transducers
Authors: Johnson Michael P.
Published: October 2005

In recent years, the bandwidth of sonar arrays has been increasing, requiring wide bandwidth transducer element designs. Tonpilz transducers have come to be the dominant element design in such arrays. The location of the fronting blocks flexural resonance relative to the operating band becomes a critical feature of these wideband element designs. In some cases, unexpectedly low electromechanical coupling and resonance frequencies have occurred. These results are typically attributed to “cross modes” due to ceramic stack geometry or interface compliance at the stack ends, though no conclusive evidence exists for either. In a series of modeling investigations utilizing the piezoelectric capabilities of the commercial finite element code ANSYS, mode shapes at the fundamental resonance of a number of designs were compared. In certain designs, excessive and unsuspected bending motion in the fronting block was found to degrade the electromechanical coupling and resonant frequency. The results of these investigations will be presented along with some possible solutions.
Formant estimation from noisy voiced speech
Authors: Krishnamurthy A. K. , Li J. , Moses R. L.
Published: October 2005

This paper considers the estimation for formant frequencies and bandwidths from voiced speech signals that are degraded with additive white noise. Each period of the speech signal is divided into the open and closed glottal phases using the electroglottograph signal. The speech signal in the closed phase is modeled as the sum of damped sinusoids, with each sinusoid corresponding to one formant. The analysis procedure thus leads to an estimate of the frequency, bandwidth, and energy of each formant. The results indicate that typically just three formants account for most of the energy in the closed phase. The noise-robustness properties of the algorithm are increased by using a total least-squares approach in obtaining the parameters and by using data from multiple consecutive closed phases. This work verifies and extends the results of S. Parthasarathy and D. Tufts [IEEE Trans. Acoust. Speech Signal Process. ASSP-35, 1241–1249 (1987)]. [Work supported by the OSU Seed grant program.]
Acoustic interaction effects in unbaffled transducer arrays
Authors: Audoly Christian
Published: October 2005

To calculate the transmitting characteristics of a transducer array, it is often necessary to take into account the acoustic interaction effects. For an array of pistonlike transducers set on planar surfaces, the model most commonly used is to assume the pistons set in an infinite rigid plane. This is not adequate when the array is not baffled, and when its dimensions are comparable to the wavelength. A theoretical model, using the combined Helmoltz integral equation method, is developed to calculate the mutual impedance matrix, the transmitting characteristics, and farfield directivities for arbitrary antenna geometries. Some results are compared to analytical models and to experiments. It is shown that the unbaffled condition produces important effects on the directivity functions and that the acoustic interactions modify the pressure distribution on the surface of the array.
The influence of whole-body vibration on noise-induced hearing loss: A review of animal experiments
Authors: Hamernik Roger P. , Ahroon William A. , Davis Robert I. , Henderson Donald
Published: October 2005

There is the suggestion in the literature that vibration may potentiate the effects of noise and may pose an increased risk of hearing loss. However, in human experimental studies, which, by necessity, are limited to low levels of TTS, the effects measured are consistent but relatively small. A very limited number of animal studies have also shown an enhanced hearing loss, but the scope of these studies is limited by a large intersubject variability and a small number of subjects. Also, the high levels of stimulation that were used in some of these animal experiments were not realistic. Our recent animal studies (chinchilla) have used a 30 Hz, 3-g-rms cage vibration in combination with continuous noise (95-dB, 0.5-kHz octave band) and impact noise (113-, 119-, or 125-dB peak SPL) exposure paradigms. All exposures lasted for 5 days. The impact noise exposures were designed to have an equal total energy. Temporary (compound) and permanent threshold shifts were measured using evoked potentials. Sensory cell populations were evaluated with the surface preparation technique. The results obtained from each of the above paradigms were consistent in showing that the presence of vibration did not have a statistically significant effect on hearing thresholds. A parallel set of experiments using a 20 Hz; 2-g-rms vibration is in progress. Preliminary conclusions are essentially the same as those of the 30-Hz experiments. The suitability of the chinchilla as an animal model for use in vibration experiments will also be discussed. [Work supported by NIOSH.]
Combined effect of whole-body vibration and noise on the dopamine turnover in the rat brain
Authors: Okada Akira , Nakamura Hiroyuki , Nakamura Hideki , Nohara Seiichi
Published: October 2005

In order to clarify the combined effects of whole-body vibration and noise on dopamine (DA) metabolism within the brain, which is known to regulate the response of the organism to various stimuli, the DA turnover rate in regions of the rat brain was determined. The rats were divided into five groups: (1) control; (2) wholebody vibration (4 G, 20 Hz, 90 min) exposure alone; (3) noise [70 dB(A), 90 min] exposure alone; (4) noise [100 dB(A), 90 min] exposure alone; and (5) combined exposure for 90 min to whole-body vibration (4 G, 20 Hz) and noise [100 dB(A)]. Changes of plasma corticosterone levels were examined as indices of the pituitary-adrenal function (PAF). The whole-body vibration exposure alone caused increases in the DA turnover rate [an increase of homovanillic acid (HVA) or HVA/DA] in the frontal cortex and nucleus accumbens. Noise exposure alone caused metabolic increases in the amygdala. The combined effect of whole-body vibration and noise on the DA neuron systems suggested that the response of the PAF to the combined stimulus was greater than that to each stimulus alone.
Results of periodic medical examinations of workers who are exposed to combined noise and vibration
Authors: Ruppe Klaus , Enderlein Gottfried
Published: October 2005

Synergistic effects of combined exposures to noise and vibration on hearing loss have been recognized under laboratory conditions by some authors. However, there are few studies of the chronic effects of combined workplace factors upon workers. An evaluation of the results of periodic medical examinations of workers who have been exposed to combined exposures during a great part of their working life showed a significant influence of the combination of factors upon hearing loss. In a population of 270 000 male workers, 52.6% were exposed to noise with levels more than 85 dB(A), 15.0% to whole-body vibration (WBV), and 4.1% to hand-arm vibration (HAV). Exposure to noise occurred in 70% of workers also exposed to WBV, and in 80% exposed to HAV. Hearing loss (more than 30 dB in 4 kHz) occurred in 16.7% of the group of workers with exposure to noise alone, but in 18.5% of the group of workers with combined exposure to noise and HAV. The prevalence of medical findings and a restricted capacity to work were significantly higher in the groups with combined exposures.
Vibrotactile intensity difference thresholds measured by two methods
Authors: Gesheider George A. , Bolanowski Stanley J. , Verrillo Ronald T.
Published: October 2005

The difference threshold for the detection of changes in vibration amplitude was measured as a function of the intensity and frequency of stimuli delivered through a 2.9-cm2 contactor to the thenar eminence. Stimuli were either 25- or 250-Hz sinusoids or narrow-band noise centered at 250 Hz or wideband noise. Thresholds were measured by two-interval forced-choice tracking under two methods of stimulus presentation. In the twoburst method, subjects had to judge which of two 700-ms bursts of vibration separated by 1000 ms was more intense. In the increment-detection method, subjects had to detect an increment in the amplitude of vibration. Thresholds were consistently lower for detecting increments in the amplitude of continuous vibration than in detecting amplitude differences between successive bursts. Amplitude increment detection, however, was relatively poor when the standard stimulus was brief rather than continuous. The near miss to Weber's law was found for both sinusoidal and noise stimuli under both methods of stimulus presentation. The difference threshold was not affected by stimulus frequency. [Work supported by NIH.]
Changes in breath sound spectra with early development of the human respiratory tract
Authors: Slawinski Elzbieta B. , McMillan D. D. , Jamieson D. G.
Published: October 2005

Breath sounds in prematurely born infants are thought to be less “vesicular” than in term infants. This difference in sound quality in newborns of various gestational ages can be explained by different transmission characteristics of lung parenchyma. Chest sounds of 27 infants, of gestational ages between 30 and 40 weeks, were recorded at different chest locations. The results show that there is a strong correlation between chest sounds of normal babies and the location of the recording microphone on the infant's chest. The spectra of inspiration of normal term babies recorded at the level of the lower posterior chest, show dominating amplitudes in the lower frequencies (350 Hz). Sounds recorded at the upper posterior chest, show spectra with enhanced amplitudes in a broader range of higher frequencies (300–900 Hz). The studies also suggest the existence of a marked difference between breathing patterns of prematurely and term born infants. Sounds of premature babies tend to have a lower overall intensity, and spectra with dominant amplitudes in a narrower bandwidth. Moreover, dominant amplitudes are shifted toward higher frequencies as compared to sounds recorded in term infants.
Wave motions in some composite and layered media
Authors: Junger Miguel C.
Published: October 2005

Fluid- and structure-borne waves are governed by the balance between elastic and inertia forces embodied, respectively, in the compliance and density of the wave-bearing medium. This paper is concerned with a class of composite and layered media where compliance is dominated by one medium and density by another. Examples of this situation are: flexible conduits containing a liquid, e.g., blood vessels; bubble swarms; porous elastic solids with Poisson's ratios in excess of one-third; compliant layers in contact with a liquid, e.g., sedimentary ocean bottom containing gas bubbles or a compliantly coated structure immersed in a liquid.
Water-structure interaction effects in stick-slip bearing vibrations of a submerged frame structure
Authors: Amick Hal
Published: October 2005

Low-frequency vibrations of a hinged, submerged steel-frame structure were observed during rotation at several speeds. The vibrations had not been observed during operation in air prior to submersion. The vibrations were attributed to stick slip of the submerged hinge bearing caused by high friction. The vibrations were measured and the characteristics of the vibrations appeared to change with rotational speed. A finite element analysis of the gate, which included the “added mass” effects of the water, disclosed that the slip frequencies corresponded to several natural modes of the gate framework. A finite element analysis of the dry structure (without added mass) indicated much higher frequencies for these modes, suggesting that displacements associated with stick slip in the dry structure would not have been large enough to have produced observable vibrations.
Temporal location of syllabic tonal target in standard Chinese
Authors: Wu Zongji , Ren Hongmo
Published: October 2005

The understanding of the dynamic nature of the syllable has been deepened by investigating the P center/stress beat and segmental target concentration (Ren, 1986). This study is concerned with another feature, the temporal location of syllabic tonal target in a tone language, Chinese. Chinese has four syllabic tones with the phonological forms H, LH, L, HL, respectively, realized by changes in F0. Our acoustic data from three speakers shows that (1) in contrast to the anticipatory cross-syllable coarticulation at the segmental level, the cross-syllable tonal transition is a carryover, (2) with a conflicting preceeding tonal context, the temporal location of the only tonal target in H and L and the first target in LH and HL depends on the rate of F0 transition starting from the syllable onset, (3) with a harmonic preceding tonal context, the first target in LH and HL is located very close to the consonant offset or the vowel onset. The relations between P center/stress beat and tonal target in case (3) call for further investigation.
Cross-language perception of a place-of-articulation contrast: The influence of nonspecific linguistic experience
Authors: Polka Linda
Published: October 2005

There is some debate whether the effects of experience on perception of nonnative speech contrasts reflect psychoacoustic, phonetic, or phonemic factors. The present study addresses this issue by comparing the performance of native English speakers and native speakers of Farsi (Persian) on perceptual categorization of ejective uvular and velar stops in Thompson (a North American Indian language). While the ejective manner class is not represented in the phonetic inventory of either English or Farsi, the uvular-velar distinction has a different phonological status in the two languages. In English, the uvular-velar place contrast is not a phonemic distinction. In Farsi, this place distinction is phonemic for voiced (nonejective) stops. To evaluate the effect of this phonological status difference, perceptual categorization of multiple natural exemplars of Thompson /k/ and /q́/ (produced in the same vowel context) was assessed in both language groups. Subjects completed both an identification test and a name-identity (categorical) same-different discrimination test. Results are discussed as they address the role of phonetic (articulatory feature similarities between native and nonnative phonologies in perception of nonnative speech contrasts. [Research supported by NINCDS and NICHD.]
Native and nonnative perception of voicing in English
Authors: Fokes Joann , Bond Z. S.
Published: October 2005

Naturally produced stop-vowel syllables (pea/bee, pie/bye, tea/dee, tie/dye) were selected to represent various voice timing values from the prevoiced, unaspirated, and aspirated ranges. The set of tokens included some intended voiced and intended voiceless stops produced with the same voice onset timing (VOT) values within the range + / − 15 ms. Native and nonnative English speakers identified three repetitions of each syllable in random order for a total of 96 test items. As expected, American English listeners judged all values in excess of 40 ms. VOT as voiceless, and all other values as voiced. In almost all cases, nonnative listener responses were predictable on the basis of their native language. Since Chinese and Japanese contrast stops on the basis of aspiration, listener judgments were almost identical to the American. On the other hand, Malaysian listeners identified all voiceless and voiced stops as intended by the speakers; that is, listeners based voicing judgments on other properties of the syllables than voice timing values. The Arab judgments were almost identical to the American for the alveolar stops /t,d/ but showed considerable uncertainty for the labial stops /p,b/. Bengali speakers also followed the American voicing pattern but showed some confusion for words containing the diphthong /ai/.
Formant onset duration: A secondary cue for identifying the place of articulation in stop consonants
Authors: Garudadri H. , Beddoes M. P. , Gilbert J. H. V. , Benguerel A. P.
Published: October 2005

Formant onset duration (FOD) is suggested as a possible alternative to voice onset time (VOT), to characterize the place of articulation in stop consonants. The FOD is defined as the duration from the start of the burst (denoting consonantal release) to the start of the formant structure (denoting vowel onset). In many languages, VOT is the most salient cue distinguishing between voiced and voiceless stop phonemes. Although VOT has been shown to increase in duration from bilabials to alveolars to velars [Lisker and Abramson, Word 20; Zue, Tech. Rep. 523, MIT], attempts to use VOT as a cue to place of articulation [Kewley-Port, J. Acoust. Soc. Am. 73, 322–335 (1983)] were not successful. In a recent study of stop consonants using the partially smoothed Wigner distribution [Garudadri et al., J. Acoust. Soc. Am. Suppl. 1 82, S55 (1987)], FOD and F2 of the following vowel were used along with the spectral shape during the burst, to resolve context dependencies due to coarticulation effects. The FOD increases from bilabials to alveolars to velars and appears to be related to the inertia of the articulators. Unlike VOT, FOD is always positive and corresponds to the vocal tract rather than the source of excitation. Evidence from English, Telugu, and French stop consonants supporting these ideas is presented. [Work supported in part by NSERC, Canada.]
Prenasalized stops and speech timing
Authors: Maddieson Ian
Published: October 2005

Prenasalized stops raise a number of interesting questions concerning the relationship between phonological units and timing in speech. Fijian is a language in which prenasalized stops are incontrovertibly single segments from the phonological point of view. It has two stop series, voiced prenasalized and voiceless oral. All syllables are open and no consonant clusters occur. Hence, this is a particularly appropriate language in which to examine these questions. Utterance-initial and word-medial prenasalized stops at bilabial, alveolar, post-alveolar, and velar places of articulation were examined in a set of words spoken by 11 speakers representing three main varieties of Fijian. Acoustic duration was measured from onset of nasal murmur to stop release (the stop component of a prenasalized stop is usually very brief and was not measured separately). Initial prenasalized stops are significantly shorter than medial ones. Medial prenasalized stops are comparable in duration to intervocalic laterals and voiceless stops, but initial prenasalized stops are significantly longer than the initial nasals in unstressed syllables which occur in the data set. Vowel length before prenasalized stops is comparable to that before other consonants. These results indicate that the role of prenasalized stops in the timing pattern of Fijian is generally similar to that of other single segments. In particular, they do not act like a consonant sequence.
Voiced speech model including source-tract interaction
Authors: Krishnamurthy A. K. , Li J.
Published: October 2005

This paper considers the problem of estimating the parameters of a voiced speech model that includes the effects of source-tract interaction. Based on work by Ananthapadmanabha and Fant [Speech Commun. 1, 167–184 (1982)], the voiced speech signal is modeled as the output of a time-varying vocal tract filter excited by a parametrized glottal source waveform. The glottal source waveform [Fant et al., STL/QPSR (1984)] models the main pulse shape of the glottal volume velocity and is described by four parameters. The effect of source-tract interaction is modeled by varying the frequency and bandwidth of the first formant in synchrony with the glottal source waveform. An analysis-by-synthesis approach is used to estimate the parameters of the model. Algorithms for estimating the parameters of the glottal source waveform and the vocal tract filter are described. Comparisons of the spectrum of the original and synthesized speech waveforms are presented. [Work supported by the OSU Seed grant program.]
A real-time frequency-shift decoder for the last transmission of Korean Airlines flight 007
Authors: Schlatter John D. , Atlas Les E.
Published: October 2005

On 1 September 1983, Korean Airlines flight 007 was intercepted and destroyed by a Soviet jet fighter after straying into Soviet airspace. Although the flight recorder from KAL 007 was not recovered, its final transmissions were recorded at a Tokyo air traffic control center. The intelligibility of the KAL 007 transmissions is compromised by at least three types of distortion: broadband background noise, narrow-band noise tone, and frequency-shift distortion. This paper describes a DSP system that has been developed to counteract the frequency-shift distortion. The system employs Hilbert transform-based techniques to introduce a linear compensating frequency shift, the extent of which may be controlled manually by the user or automatically by a separate computer. Tests performed to date with the system on the KAL 007 transmissions have shown it to be a useful tool. Intelligibility improvements have led to independently verified advances in understanding several of KAL 007's final transmissions.
On the semantic content of intelligibility test material on assessing signal processing algorithms
Authors: Benson P. , Naylor J.
Published: October 2005

Signal processing algorithms can be used to enhance speech intelligibility by improving the detectability of important acoustic features. It should follow from this that other nonacoustic portions of the signal are a source of experimental error that should be controlled. Nevertheless, certain signal processing techniques produce reliable improvements in intelligibility only when that speech is meaningful. A series of intelligibility tests was carried out with co-channel speech, which combines the speech of two talkers into a single channel. This speech had been processed using the harmonic magnitude suppression (HMS) technique [Naylor and Boll, ICASSP (1987)] to diminish the effect of the louder talker. Intelligibility testing using target speech of read PB sentences masking read four-word nonsense sentences revealed no differences between treated and untreated speech. Intelligibility using complete sentences as both masker and target showed significant differences in favor of the HMS treated speech. An analysis of signals and errors will be presented to show how listeners are integrating information from nonsignal sources to improve performance.
Preliminary study of multilevel peak-clipped and time-quantized speech
Authors: O'Brien Edward M. , Pogue David J.
Published: October 2005

Speech was amplified to a level of plus and minus 5 V for analog-to-digital conversion (sampling rate of 20 kHz). It was then quantized to five discrete levels. The 0-V level was used for speech within the squelch level (squelch was used to mask background noise). Positive speech waves above A volts were assigned a value of 5 V. Speech waves with peak values below this level were assigned a value of A volts. Negative speech waves were quantized to either − 5 V or − A volts similar to the processing of the positive speech waveforms. Processing was done with a PC. Two different A levels were tested on monosyllabic word lists. The first was at the level of the rms value of each word (average rms level across all words was 1.22 V). The second level was at a fixed value of 2 V. Preliminary results yielded a higher percentage word intelligibility. This type of speech processing has application to the development of a tactile hearing aid.
Singing synthesis and composition
Authors: Bennett Gerald
Published: October 2005

Apart from its interest as a confirmation of experimental hypotheses, singing synthesis can be of great importance in contemporary composition. The experience of many composers with the program CHANP, developed at IRCAM, shows that a sound synthesis program based on a specific physical model can serve as a general purpose synthesis tool, while remaining intuitively manageable. The particular structure of the program CHANP offers the possibility of defining both the local structure of the sound itself and the larger scale structure of the composition. Musical examples will illustrate both vocal and nonvocal sounds taken from electroacoustic compositions.
The jnd's for rate and extent of frequency modulations
Authors: Horii Yoshiyuki , Scherer Ron
Published: October 2005

Vocal vibrato samples were spectrographically analyzed to determine ranges of rate and extent of frequency modulations. Subsequently, sinusoidal and pulse signals of 2-s duration at 261 or 522 Hz, modulated within the measured ranges, were used as standard stimuli to derive rate and extent jnd. For the rate jnd, the standard stimuli were sinusoidally modulated at 4, 5, and 6 Hz. For the frequency extent jnd, the standard stimuli were sinusoidally modulated at 5 Hz with frequency extent of 0.25, 0.5, and 0.75 semitones. Subjects were instructed to adjust rate/extent of frequency modulations until the difference between the standard and adjustable signals was just noticeable. The rate jnd was less than 5%, while frequency extent jnd was much smaller especially for the pulse stimuli. A perceptual cue for the frequency extent appeared to be rate of frequency changes rather than the extreme frequency values. A follow-up experiment indicated listeners' inability to match accurately nonmodulated signal frequency to the extreme frequency values of the modulated signals. Implications of these findings to vibrato singing will be discussed. [Work supported by NIH.]
Comodulation masking release with delayed signal onsets
Authors: Wright Beverly A. , McFadden Dennis
Published: October 2005

The detectability of a 1250-Hz, 50-ms signal was assessed in a comodulation masking release (CMR) setting. One 50-Hz noise band (the “masker”) was centered at 1250 Hz; other noise bands were centered at 850, 1050, 1450, and 1650 Hz (the “cue” bands). The masker and/or cue bands were gated prior to the onset of the signal by an amount (“fringe”) that was varied across blocks of trials. The noise bands and the signal always ended together. The temporal envelopes of the noise bands were all correlated, all correlated except for the masker band, or all uncorrelated. When all of the noise bands were gated synchronously, the CMR grew from 1 dB in the burst condition to 7 dB for a 450-ms fringe, due to a greater improvement in detectability in the correlated condition compared to the uncorrelated and all-uncorrelated conditions. When the cue bands were gated before the masker, the average CMR was larger (4–6 dB) than when the masker was gated before the cue bands (2–4 dB). These differences in improvement with increasing fringe duration may be attributable to differences in neural adaptation in the correlated and uncorrelated conditions. [Work supported by NINCDS Grant NS15895.]
Gap detection in a narrow-band noise with either a comodulated or a noncomodulated flanking band
Authors: Grose John H. , Hall Joseph W.
Published: October 2005

Comodulation masking release (CMR) suggests that the auditory system is sensitive to across-frequency differences in modulation pattern. This raises the question of whether it is as sensitive to modulation differences due to the absence of activity (a silent interval) as it is to the presence of additional activity (a signal). If so, gap detection in a narrow-band noise would be expected to be better in the presence of a comodulating flanking band than in the presence of a noncomodulating flanking band. The present study was designed to test this hypothesis. Gap detection was measured in a 30-Hz-wide narrow-band noise centered at 1 kHz. A second 30-Hz band of noise, centered at either 500 Hz or 1.5 kHz, was then added that was either comodulated or noncomodulated with the 1-kHz band. While gap detection deteriorated with the addition of a second noise band, it appeared to do so more for the noncomodulated case than for the comodulated case. [Research supported by AFOSR.]
Detecting amplitude modulation of sinusoidal carriers
Authors: Yost William A. , Sheft Stanley
Published: October 2005

Listeners were asked to detect sinusoidal amplitude modulation (SAM) of one carrier tone (the target carrier) in the presence of a second carrier tone (the masking carrier) that also had SAM. The depth of modulation required to detect the presence of SAM of the target carrier was measured as a function of the difference in the frequency of amplitude modulation for the two carriers (modulator frequencies ranged from 4 to 100 Hz), the frequency separation between the two carriers (200- to 3000-Hz separation), and the phase of the sinusoidal modulator of the masker carrier relative to the phase of the sinusoidal modulator of the target carrier. In half of the conditions, the frequency of the target carrier was greater than the frequency of the masker carrier, while, for the other half of the conditions, the frequency of the target carrier was less than that of the masker carrier. The data will be discussed in terms of the strategies employed by the auditory system in processing temporal modulation of complex sounds. The data indicate that the auditory system uses a wideband mode for processing temporal modulation, such that there is a great deal of interaction across widely separate frequency channels. [Work supported by the NINCDS.]
Rough interface scattering
Authors: Berman David H. , Dacol Dalcio K. , Perkins John S.
Published: October 2005

Recently, there has been a great deal of work on scattering by rough surfaces. Most of this work is aimed at describing scattering from the sea surface, and so Dirichlet boundary conditions are used. However, there are situations in which energy transmission across a boundary is important, such as in scattering from the seafloor. Hence, scattering by rough acoustically penetrable surfaces is considered. Methods for calculating such scattering will be briefly reviewed. Results obtained by the “point-matching” method will be presented for fluid-fluid and fluid-solid interfaces, both deterministic and random. Solutions of these problems yield forward and backscattering strengths of the seafloor, ice canopies, as well as the sea surface. In addition, it is possible to determine the probability distribution of scattered energy. These exact results will also be used to evaluate various approximation schemes.
Application of the finite element method to simulating VLF/ULF under-ice acoustic propagation and scattering
Authors: Chin-Bing Stanley A. , Murphy Joseph E.
Published: October 2005

A full-wave range-dependent ocean acoustic propagation and scattering model based on the finite element method [J. E. Murphy and S. A. Chin-Bing, J. Acoust. Soc. Am. Suppl. 1 82, S61 (1987)] has been applied to a shallow-water under-ice scenario at very low to ultra-low frequencies (VLF/ULF) and at extreme close range. The model has the advantage that it includes the coupled effects of the full-wave range-dependent forward propagated and backscattered fields. (However, the madel does not yet include the effects of shear waves.) The under-ice surface was simulated by a fractallike interface superimposed on an ice keel representation. At very low frequencies, the acoustic wave can penetrate the ice-water interface and undergo reflection at the air-ice interface. The reflected, refracted, and backscattered waves couple to produce interesting interference effects. Numerical simulations will be presented that examine the placement of receivers for optimum signal detection at these low frequencies. [Work supported by ONR/NORDA.]
Field and numerical volume scattering experiments
Authors: Ewart Terry E. , Reynolds Stephen A.
Published: October 2005

Until recently, the history of comparing ocean acoustic volume scattering experiments with theory bore scant resemblance to the traditional scientific method. However, vastly improved agreement between predicted and observed intensity correlations is now seen. It is clear that two elements of the research have played vital roles in reaching the current understanding. The first is the development of theories that include the parametrizations and approximations appropriate to the ocean case. The second is the characterization of the deterministic and stochastic processes of the ocean that give rise to the observed fluctuations. An overview of those processes relevant to the study of ocean volume scattering is presented, followed by a discussion of where attention needs to be focused in order to expand our understanding of volume scattering. Results from the 1971 experiment at Cobb Seamount, the 1977 Mid-Ocean Acoustic Transmission Experiment, the 1985 AIWEX Acoustic Transmission Experiment, and numerical experiments provide the framework for the discussions. [Work supported by ONR.]
Acoustic detection in the weak scattering region of an oceanic internal wave field
Authors: Bates Bruce J.
Published: October 2005

The coherent pressure field of an acoustic harmonic point source is gradually transformed into an incoherent pressure field as a function of propagation distance through the oceanic internal wave field. A receiver located in the weak scattering region would measure a fluctuating acoustic pressure with a Gaussianly distributed logarithmic amplitude and phase. The consequence is a biased estimate for the conventional maximum likelihood estimate of pressure or intensity and subsequently a biased detection criteria. It is proposed that detection performance may be improved in this case by logarithmically transforming the pressure prior to detection processing. An analysis and discussion will be presented using the Garrett and Munk internal wave field model. [Work supported by NUSC IR/IED.]
The dispersion of sound in monoatomic gases
Authors: Ford George W.
Published: October 2005

The classical Kirchhoff derivation of the absorption of sound in gases at moderate pressures starts from the Navier-Stokes equations of hydrodynamics. At low pressures, specifically when the mean free path is no longer small compared with the sound wavelength, this same derivation predicts a dispersion of the speed of sound. The absorption and dispersion can also be derived directly from the Boltzmann equation, with a result that confirms the Kirchhoff absorption coefficient, but with predicted dispersion and higher-order terms in the absorption that differ from those of hydrodynamics. Martin Greenspan's early work on sound propagation at low pressures provided the experimental data for a definitive test of the Boltzmann equation. These derivations will be briefly reviewed and the comparison with Greenspan's results will be shown. Some concluding remarks about the history of this problem and about more recent developments will be made.
Delta streams for English synthesis
Authors: Hertz Susan R.
Published: October 2005

Although speech patterns are heavily influenced by the hierarchical linguistic structure of speech, synthesis by rule systems have generally been based on linear utterance representations. Delta is a new programing language that makes it easy to work with utterance representations containing multiple levels. Both higher level linguistic units, such as phrases, syllables, and phonemes, and lower level phonetic events, such as articulatory or formant targets and F0 trends, can be easily accommodated on separate interconnected “streams,” with each unit equally accessible to the rules. While Delta can be used to test most any synthesis model for any language, this paper will show how Delta can be used to test a particular model for English. This model uses, among others, CV, syllable, nucleus, phoneme, formant, and duration streams, with formant transitions represented as duration tokens that are in effect invisible in other streams. The paper will justify the selection of streams and the unique way of handling formant transitions, demonstrating in Delta notation how the model leads to particularly straightforward rules for predicting English phoneme durations, formant values, and aspiration patterns.
The smoothed pseudo-Wigner distribution in speech analysis
Authors: Khadra Labib M.
Published: October 2005

Recently, a great deal of interest has been shown in applying the Wigner-Ville distribution to obtain time-frequency energy representation of nonstationary signals. The utility of the Wigner distribution has proved useful in analyzing monocomponent signals. In the case of multicomponent signals, the Wigner distribution adds cross terms without any physical significance to the time-frequency distribution. The presence of cross terms obscures the actual spectral features of interest and makes the results very misleading. To apply the Wigner-Ville distribution to speech signals, it is essential to remove all cross terms not of interest. This problem may be solved by smoothing the Wigner-Ville distribution independently in time and frequency directions using the “smoothed” pseudo-Wigner estimator. This estimator possesses several advantages over the short time periodogram. This presentation will concentrate on the application of the smoothed pseudo-Wigner distribution (SPWD) to speech signals and will demonstrate the ability of the SPWD to improve the quality of the time-frequency representation of speech signals. In particular, a comparison will be made between the spectrogram and the SPWD, and it will be shown how high-frequency spectral features may be easily detected from an SPWD but are far less obvious in the spectrogram. Moreover, it will be shown that the SPWD is more appropriate for the analysis of formant structure.
Acoustic sources in the turbulent boundary layer
Authors: Hardin J. C.
Published: October 2005

This paper will be concerned with sources of sound in the simplest case of a turbulent boundary layer over a flat plate. For the majority of the paper, the driving flow will be considered to be subsonic such that gross compressibility effects, such as shocks, do not occur. Standard terminology, governing equations, and characteristics of the turbulence in the boundary layer and the noise it produces will be described. The paper will then examine the fundamental instability of this flow at high Reynolds number and the transition of a laminar boundary layer to turbulence. Generation of Tollmien—Schlichting waves and the myriad large scale structures (hairpin vortices, streaks, spots, bursts, etc.) that have been observed in boundary layers will also be described. Finally, the theoretical understanding of noise production by this flow, which was initiated by Lighthill, Curle, and Powell and carried on by later research workers, will be described. In particular, the use of different Green's functions, which allows the noise to be determined either through integration of various flow quantities over the volume of the boundary-layer flow or by integration of the pressure over the flat plate, will be developed and the advantages of each noted. In light of this understanding, mechanisms for boundary-layer noise production and methods for their calculation are discussed. Additiolaal sources in high-speed boundary layers with shocks present will also be described.
Extended frequency response of a fiber-optic microphone
Authors: Zuckerwar Allan J. , Areford Mathew L.
Published: October 2005

A condenser microphone responds to the mean displacement of a stretched membrane excited into an axially symmetric mode of vibration. At some frequency between the first and second resonant frequencies, the mean displacement falls to zero and the microphone response drops sharply after the first resonance. A fiber-optic microphone, on the other hand, responds to the displacement at the center of the membrane. The center displacement of an axially symmetric mode never falls to zero. Consequently, through judicious backplate design, the membrane motion can be damped to achieve a smooth merger in response between the first and second resonances, and the bandwidth of the microphone can be extended to beyond the second resonant frequency. After a brief review of the construction of the condenser and fiber-optic microphones, the results of a theoretical analysis will be presented for two cases: (1) a B&K 12-in. condenser microphone compared with its fiber-optic equivalent, and (2) 18-in. fiber-optic microphone of special design to measure pressure fluctuations in a turbulent boundary layer.
Rayleigh's philosophy of problem solving, as inferred from his original papers on acoustics
Authors: Pierce Allan D.
Published: October 2005

Rayleigh not only had a knack for skimming off the cream, but also for finding cream where others might have thought there was no cream to be found. His first substantial work of note, the 1870 memoir on resonance in the Philosophical Transactions, introduced a style and philosophy that is evident in many of his later works and that is worth emulating. In this paper, Rayleigh successfully bypassed the elegant but difficult to apply mathematics of Helmholtz's epochal 1860 paper, and substituted instead a few simple approximate concepts and produced some relatively simple formulas that could be compared with Sondhauss's experimental results on what we now call Helmholtz resonators. Other examples cited in the present paper are Rayleigh's theory of diffraction by orifices and slits, his analytical models for elastic shells, his discovery of adiabatic invariants in his 1902 “pressure of vibrations” paper, and his approach to modeling low-frequency sound radiation from sources. Rayleigh's work and philosophy may have had a substantial influence, although perhaps not consciously recognized, on modern trends such as finite elements and matched asymptotic expansions. In addition to a thorough familiarity with basic physical concepts, a good intuitive feel for what was relevant, and an inherent love of simplicity, Rayleigh made extensive use of variational techniques as a framework for developing approximations. Hitherto they had been used primarily as a means for elegant expression of basic principles. Also noteworthy was Rayleigh's heavy use of similitude arguments. [Work supported by ONR.]
Lord Rayleigh and reciprocity in physics
Authors: Cook Richard K.
Published: October 2005

In The Theory of Sound, Rayleigh presents his analysis of the reciprocal theorem of mathematical physics with the observation that “Very remarkable reciprocal relations exist between the forces and motions of different types….” in a linearized dynamical system. He introduces the reciprocity principle for sound waves in an air-filled space: “On his extension of Green's theorem, Helmholtz founds his proof of the important (reciprocal) theorem contained in the following statement: ….” In the ensuing 100 years since publication of his book, the reciprocity principle has been extended to many areas of physics—electrodynamics, electroacoustics, piezoelectricity, electromagnetic waves, optics, etc. The principle has been successfully applied in electroacoustics to achieve a system for accurate, absolute calibration of microphones used for acoustical measurements. The system is now internationally used by standards laboratories. Limitations and restrictions on applicability of the reciprocity principle to certain physical systems have come to light. Conspicuous examples involve the propagation of sound in moving air and the propagation of electromagnetic waves through magnetized media.
Lord Rayleigh's contributions to aeroacoustics
Authors: Powell Alan
Published: October 2005

The growth of aeroacoustics as a distinct discipline burgeoned at midcentury, initially fostered by the need to control jet noise. It merged the then separate disciplines of aerodynamics and sound. Rayleigh knew no such boundaries and would likely have made major contributions to aeroacoustics if the fundamental questions had captured his attention. As it was, he wrote on many highly pertinent aspects: e.g., his theory for sensitive flames and jets (visual sound indicators) led to the modern instability theory of jets and other important aerodynamic flows, while the hypothesized feedback in his “bird-call” (a compatible high-frequency sound source) is similar to that in edge tones and in many other flow resonances. These had puzzling inconsistencies until Rayleigh's method of similitude was applied through Reynolds and Strouhal numbers. He had applied it to Strouhal's aeolian tones and to the scattering of sound from inhomogeneities, in which he introduced the “acoustic model” of aerodynamic sound theory (and in which the method for Rayleigh's integral was used for plane boundaries). There are now hundreds of research publications in aeroacoustics, some notable books and a place in university education: Rayleigh's name occurs many times.
Acoustic phase measurements from volume backscatter
Authors: Huston R. Del
Published: October 2005

Stable and useful measurements of the orientation of the acoustic signal vector or acoustic phase as a function of range and time can be obtained from volume backscatter. Individual targets that are normally random and sparse relative to the acoustic wavelength, yield echoes with random phases between independent realizations. This difficulty has been overcome by complex superposition of echoes from successive transmissions, such that the effective density of acoustic targets progressively increases as the summation proceeds. The theoretical basis of this type of coherent processing has been developed and examined in the limiting case, in which it approximates a scatterer continuum. The theory provides fundamental insights to the behavior of both the amplitude and phase of composite echoes from a volume mirror. Experimental work in Saanich Inlet, B.C. serves to confirm the theoretical concepts through arms difference measurement of the acoustic phase which removes fluctuations from the evolving sound-speed profile. Based on these results, the potential for new types of oceanographic measurements using these techniques appears both realistic and encouraging.