bluuebunny/crossref_metadata_2025 huggingface dataset:
Re-examination of the role of the human acoustic stapedius reflex
Authors: Phillips Dennis P. , Stuart Andrew , Carpenter Michael
Published: July 2002

The “rollover” seen in the word recognition performance scores of patients with Bell’s palsy (facial nerve paralysis) has historically been taken as an indicator of the role of the stapedius reflex in the protection from upward spread of masking. Bell’s palsy, however, may be a polyneuropathy, so it is not clear that the poor word recognition performance at high levels is necessarily attributable specifically to impaired facial nerve function. The present article reports two new experiments that probe whether an isolated impairment of the stapedius reflex can produce rollover in word recognition performance-intensity functions. In experiment 1, performance-intensity functions for monosyllabic speech materials were obtained from ten normal listeners under two listening conditions: normal and low-frequency augmented to offset the effects of the stapedius reflex on the transmission of low-frequency vibrations to the cochlea. There was no effect of the spectral augmentation on word recognition for stimulus levels up to 107 dB SPL. In experiment 2, six patients who had undergone stapedectomy were tested for rollover using performance-intensity functions. None of the patients showed rollover in their performance-intensity functions, even at stimulus levels in excess of 100 dB HL. These data suggest that if the stapedius reflex has a role in protection from upward spread of masking, then this role is inconsequential for word recognition in quiet.
Mechanisms of vocal production in budgerigars (Melopsittacus undulatus)
Authors: Brittan-Powell Elizabeth F. , Dooling Robert J. , Larsen Ole N. , Heaton James T.
Published: July 2002

Songbirds vocalizing in helium show a change in the spectral quality of their vocalizations. This effect is due to an increase in the speed of sound in helium that in turn alters the resonance properties of the vocal tract. Here, this approach is extended to a psittacine, the budgerigar (Melopsittacus undulatus), whose syringeal anatomy and innervation differ from that of a songbird. Contact calls from birds vocalizing in heliox (70/30 helium/oxygen environment) showed an overall increase in the amount of energy at frequencies above the fundamental, slight changes in the frequency of the fundamental and harmonics, and some change in the level of harmonics. Calls produced by a syringeally denervated bird showed more dramatic changes. Recordings from live birds were compared with sounds produced by various simple “artificial” tracheal and syringeal models. Results suggest that budgerigars produce contact calls using the syringeal membranes as a unitary sound source which produces acoustic energy in a narrow frequency band whose fundamental frequency is matched to the resonant frequency of the trachea. The syrinx is not normally coupled to the tracheal resonator, and resonances probably play only a minor role in shaping the spectrum of contact calls.
Fast numerical algorithm for simulation of nonlinear acoustic waves with shocks of finite thickness
Authors: Sapozhnikov Oleg A. , Khokhlova Vera A.
Published: July 2002

In an earlier work [V. A. Khokhlova and O. A. Sapozhnikov, J. Acoust. Soc. Am. 96, 3321 (1994)], a modified spectral approach was proposed for the description of nonlinear waves containing shocks. An abrupt shock has an analytical high-frequency ω−1 asymptote. This asymptotic result was used in the numerical algorithm to model strongly nonlinear waves with a relatively few number of harmonics N∼20 [Pischal’nikov et al., Acoust. Phys. 42, 362–367 (1996)]. However, in real dissipative medium the shock front is not a discontinuity, but a transition region of finite thickness. This region can be adequately described by a hyperbolic tangent profile, so that the correspondent wave spectrum at high frequencies is governed by the Fay solution. Here, the Fay spectrum asymptote of the finite thickness shock is used, instead of the ω−1 asymptote of the abrupt shock, to derive a set of coupled differential equations for the harmonic amplitudes. Several model problems are considered. It is shown that this method permits increasing the accuracy and stability of the modified spectral approach, and still leads to a reduction in the number of equations by a factor of 10–100 in comparison with direct frequency domain schemes. [Work supported by FIRCA and RFBR.]
Nonlinear effects for torsional waves in rods with cracklike defects
Authors: Didenkulov Igor N. , Ekimov Alexander E. , Kazakov Vyacheslav V.
Published: July 2002

The enormously high nonlinear response of solids with cracks to an acoustic excitation makes nonlinear methods possible for nondestructive testing (NDT). Among the problems to be solved are the mechanisms of such nonlinear responses and the development of NDT methods. Results of an experimental study of nonlinear effects for elastic waves in metal rods with cracklike defects and their dependence on the type of contacts in the cracks are given. Unlike earlier works concerned mainly with longitudinal and flexural waves in solids, the present experiment shows that a high degree of nonlinearity is found for torsional waves as well. The crack was modeled by cutting a rod and tightly filling a crack with metal plates. Two types of contact were studied: dry and lubricated contacts. Modulation of high-frequency torsional waves (20 kHz and 22.8 kHz) in a rod by low-frequency flexural vibrations was studied. Flexural vibrations were excited in two ways: with a shock and with the help of a vibrator. Amplitude modulation was observed only in a rod with a crack, the level of this modulation drastically decreasing in the presence of liquid lubricant. [Work supported by RFBR, Russia—Grant No. 97-02-17524—and by INCAS, Nizhny Novgorod, Russia.]
Acoustic modeling of oscillatory hydrodynamic loading and fluid–structure interaction
Authors: Gopinath Ashok , Sweany Gary W.
Published: July 2002

An experimental study has been conducted of forces on a cylinder in a standing acoustic wave. The cylinder is representative of the leg of an offshore structure or platform, while the acoustic field is representative of the oscillatory wave loading on such a structure. A piston oscillator drive mechanism provides the requisite large acoustic amplitudes in the pressure vessel resonator that houses the test cylinder. The use of a high-pressure gas allows the desired high values of the Reynolds numbers to be achieved. Both in-line drag forces and transverse (lift) forces on the cylinder, along with the phasing information, have been measured with the help of suitably mounted strain gauges, and corroborated with existing data in the literature. Higher harmonic forces and resonant interactions, typical of compliant structures, have also been measured and analyzed. This experimental technique appears to have a promising potential for studying the large amplitude, large Reynolds number regime of hydrodynamic loading and the resulting fluid–structure interactions.
Modification of the four-load method to compute source impedance in a pipe system
Authors: Sridhara B. S.
Published: July 2002

This paper discusses a new method used to obtain the source impedance from the four-load method. The three nonlinear algebraic equations of the four-load method were modified to give three equations of a circle. At each frequency, the intersections of these circles give the real and imaginary parts of the source impedance. A computer program was developed to calculate these intersections and extract the realistic values. A frequency range from 0 to 800 Hz was considered for a 0.2286-m (9-in.) diam pipe system with a loudspeaker as the sound source. At each frequency, the circles were scanned from 0° to 360° in intervals of 0.5° allowing small percentage errors such as 0.001, 0.005, and 0.01. The computed source impedance values were compared with those obtained from the direct method. The results agree well with the decrease in the percentage error.
Magnetic circuit design methodologies for dual coil transducers used in public sound reinforcement
Authors: Button Douglas J.
Published: July 2002

Although the electrodynamic drive topology incorporating two axially (not concentrically) placed coils is not a new idea and dates back to the 1950’s, recent interest in the design has begun a proliferation of the design concept in professional sound reinforcement loudspeakers. The fundamental design involves two coils that are opposite in phase and reside in oppositely polarized magnetic gaps, thus providing a Lorentz force in the same axial direction. The two gaps are formed from the same magnetic circuit, and both coils are wound on the same form, separated by some distance, connected or wound out of phase, and attached to a single diaphragm. The work herewithin describes different design options in magnetic materials, magnetic circuit geometries, and voice coil topologies. The focus is on performance trade-offs and advantages in weight, power handling, power compression, and distortion, relative to a single gap design. The end result being acoustical solutions with better fidelity, less weight, and size.
Experimental investigation on the transition to steady state of self-oscillation of a thermoacoustic prime mover
Authors: Zhao Bosen , Jebali Fathi , Francois Maurice X.
Published: July 2002

A thermoacoustic prime mover can be considered as a nonlinear system in which an initial small perturbation is amplified until nonlinear mechanisms lead to a new balanced state. A series of experiments were carried out to help understand the nonlinear mechanism. The transition process is divided into three periods: a growing period in which the pressure grows exponentially with time to its maximum; a falling period in which the pressure decreases to its minimum; and a period in which the pressure is restablished slowly until the steady state. A rapid decrease in temperature difference between the cold and hot heat exchangers is observed when the pressure arrives at the maximum. The difference between maximum pressure and steady-state pressure depends on the mean pressure in the prime mover: the higher the mean pressure, the greater the difference. A model of positive feedback amplifier with nonlinear resistance is proposed to describe this phenomenon.
Subjective evaluation of classical guitars
Authors: Orduña-Bustamante Felipe , Boullosa Ricardo R.
Published: July 2002

An analysis is presented of two methods for the subjective evaluation of a set of classical guitars. One is based on ‘‘blind’’ listening tests by a general audience, and another is based on direct inspection and playing by guitar teachers and students. Subjective experiments reveal that the two types of tests produce essentially the same sorting of the guitars by subjective quality. The listening test, based on pairwise comparisons of guitars playing the same musical fragment, is judged by the subjects to be a difficult task. This is also reflected in the results. Additionally, an interesting effect is consistently observed in which a higher proportion of votes is obtained by the second guitar played in each pair, despite the fact that listening to each pair of guitars lasts less than about 40 s. This seems to suggest a certain natural limit in the short-term memory abilities of the subjects in recalling the first guitar. A data processing technique is described that produces unbiased results from this type of test. The playing test, on the other hand, is judged by the players to be a comparatively easy task and the results are also more easily interpreted.
Determining the parameters of an ocean internal wave model using acoustic log-amplitude and phase—A Rytov inverse
Authors: Reynolds Steve , Ewart Terry E. , Rouseff Daniel
Published: July 2002

The feasibility of an inversion for the properties of the stochastic internal wave field using acoustic measurements is demonstrated. Certain parameters of a generalized internal wave model can be obtained for both deep- and shallow-water cases. A hierarchy of inversion scenarios has been studied using numerical simulations where the scenarios vary from extensive vertical and temporal separations to single point measurements. Because acoustic measurements intrinsically average over range, they provide an important constraint to three-space plus time stochastic models. Using acoustic data with standard oceanographic measurements provides even a more stringent set of inversion constraints. These issues are considered and how acoustics may be used to answer open questions about the properties of internal waves and other random ocean processes is examined.
A local algorithm for the determination of interior material parameters from a knowledge of elastic displacements
Authors: Romano A. J. , Shirron J. J. , Bucaro J. A.
Published: July 2002

A new method is presented for the local determination of material parameters of an isotropic, inhomogenous medium subject to time harmonic vibration. Given a knowledge of the displacements throughout the medium, a novel implementation of a variational formulation is used to determine the ratios λ/ρ and μ/ρ. A theoretical formulation is presented and validated using numerical data obtained from a finite-element method. The results indicate that the method may be applied locally within an inhomogenous medium, and that the corresponding material parameters can be recovered to a high degree of accuracy. Because the method assumes knowledge of the displacements throughout the medium, various approaches to obtaining this information will also be discussed. [This work supported by the Office of Naval Research.]
Signal processing for detection of defect using Lamb waves
Authors: Blanquet Pierrick , Demol Thierry , Moulin Emmanuel , Delebarre Christophe
Published: July 2002

Conventional ultrasonic inspection of large structures is very time consuming due to the surface scanning necessity. Since they can propagate over long distances, Lamb waves are an attractive solution to this problem. Here is shown the feasibility of using Lamb wave generation using a transducer embedded inside the material and two methods are given to determine the presence of a defect along a propagation line. In a first step, the embedded transducer is used to generate and receive Lamb waves. Then, a method based on the spatial Fourier transform is used to measure their phase velocities. The experimental measurements are in good agreement with a numerical phase velocity computation. In a second step, the determination of the presence of a defect along a propagation line is shown. One method consists in measuring the attenuation of Lamb waves during the propagation. Another one is based on the Hilbert transform, which can be used to determine mode conversions due to the damage. In both cases, the results show the feasibility of determining the presence of a defect.
Interaction of acoustical waves in concretes with cracks
Authors: Didenkulov Igor N. , Ekimov Alexander E. , Kazakov Vyacheslav V. , Sutin Alexander M. , Johnson Paul A. , Budnikov Igor N. , Bagryanov Boris V. , Denisov Mikhail B.
Published: July 2002

Two separate experiments conducted with concrete samples containing cracks illustrate that acoustical methods have promise in damage detec- tion. Samples of concrete were 2.6 m×19 cm×12 cm and 1.7 m×20 cm×20 cm for the first and the second experiments, correspondingly. Cracks were located near sample centers and had dimensions of sample sections. In one experiment, high-frequency (5.3-kHz) longitudinal or rotational waves were modulated by low frequency (3 to 200-Hz) flexural vibrations. The relative amplitude of the modulation signal was about −20 dB. When the crack was filled by water, the modulation amplitude decreased in amplitude by approximately 3–4 dB. This result is expected because fluid should diminish the nonlinearity on the crack contact. In an uncracked sample, no modulation should be observed. In the second experiment, small explosive sources (less than 100 kg/cm2) were used to study the interaction of a large amplitude, broad-band frequency pulse, with a weak impulse from small explosive source. It was first observed that the weak pulse did not propagate through the crack. The weak signal passed through the crack when a stronger explosion pulse was simulteneously applied to the bulk, transiently closing the crack. The results are two of many experiments that indicate linear and nonlinear wave methods may be applied to characterize damage in concrete. [Work supported by INCAS, Nizhny Novgorod and by RFBR Grant 97-02-17524.]
Modeling free reed behavior using calculated reed admittance
Authors: Cottingham James P. , Fetzer Casey A.
Published: July 2002

For musical wind instruments driven by a reed mechanism, Fletcher has provided an analysis which shows that a necessary condition for the sounding of an instrument is that the acoustic admittance of the reed has a real part, which is negative and greater in magnitude than the real part of the pipe admittance [N. H. Fletcher, Acustica 43, 63–72 (1979)]. The analysis also shows that inward-striking (closing) and outward-striking (opening) reeds will exhibit different behavior. Free reeds, used in instruments such as the reed organ, harmonica, accordion, and the Asian free reed mouth organs, can exhibit behavior characteristic of either opening or closing reeds, depending on the details of the configuration. Using reed parameters determined by experiment, the reed admittance as a function of frequency has been calculated for free reeds and used to make quantitative predictions. For a variety of free-reed parameters, the frequency of vibration as a function of blowing pressure has been calculated and compared with experimental results. Cases are considered in which a reed is coupled to a pipe resonator as well as cases in which the reed is not coupled to a resonator.
Acoustic analysis of simple vowels with nasal coda in standard Chinese
Authors: Chen Marilyn Y.
Published: July 2002

More than 40% of the monosyllables in standard Chinese (SC) have a vowel followed by a nasal coda. The goal of this study is to determine by acoustic analysis how the vocalic portion is affected by the nasal context due to coarticulation in SC disyllabic words. Simple vowels /i–a–e/ in two types of syllables were examined: (1) with a nasal coda /n–ng/ followed by a syllable beginning with a stop or vowel, and (2) without a nasal coda followed by a syllable beginning with a stop or /n/. Spectral measurements were made every 10 ms in the vowel and the nasal consonant. The maximum first difference for the first four formant amplitudes was used to detect the vowel–nasal consonant boundary. The formant trajectories in the vowel over time were used as indicators for the place of the nasal coda formed with or without oral closure. Contours of adjusted A1–P0 and A1−P1 (amplitude differences between the first formant and nasal peaks) over time showed that vowels with nasal coda are more nasalized than vowels in a non-nasal context or in an intersyllabic nasal context. [Work supported by MIT International Science and Technology Initiative.]
Integration of acoustic information in the perception of [s] ± stop clusters by children and adults
Authors: Crowther Court S. , Nittrouer Susan
Published: July 2002

To compare the integration of acoustic information in phonetic perception by young children and adults, second formant frequency at voicing onset (F2 onset) and gap duration were varied as cues distinguishing ‘‘spa’’ and ‘‘sa.’’ Listeners performed same–different (AX) discrimination in four conditions. The gap of the standard (A) stimulus was always consistent with ‘‘spa;’’ gaps of the comparison (X) stimuli decreased in duration along a continuum, thus becoming more consistent with ‘‘sa.’’ In the two ‘‘one-cue’’ conditions, F2 onset was the same for the A and X stimuli. In the ‘‘two-cue cooperating’’ condition, F2 onset for stimulus A supported ‘‘spa,’’ and F2 onset for X stimuli supported ‘‘sa.’’ In the ‘‘two-cue conflicting’’ condition, F2 onset for stimulus A supported ‘‘sa,’’ and F2 onset for X stimuli supported ‘‘spa.’’ Results led to three conclusions: (1) Child and adult discrimination performance was similar overall, suggesting that the child-adult differences across conditions were not due to differences in general auditory ability. (2) The acoustic cues were integrated in phonetic perception, but acoustic differences were nonetheless accessible perceptually for AX discrimination. (3) However, these acoustic differences are less accessible to adults than to children after integration in phonetic perception. [Work supported by research Grant No. 5 RO1 DC 00633 from the NIDCD/NIH.]
Effects of consonant environment on vowel formant patterns
Authors: Hillenbrand James M. , Clark Michael J.
Published: July 2002

A significant body of evidence has accumulated indicating that vowel identification is influenced by spectral change patterns. For example, a large scale study of vowel formant patterns showed substantial improvements in category separability when a pattern classifier was trained on multiple samples of the formant pattern rather than a single sample at steady state [Hillenbrand et al., J. Acoust. Soc. Am. 97, 3099–3111 (1995)]. However, in the earlier study all utterances were recorded in a constant /hVd/ environment. The purpose of the present study was to determine whether a close relationship between vowel identity and spectral change patterns is maintained when the consonant environment is allowed to vary. Recordings were made of six men and six women producing the vowels /i,I,ε,æ,■,■,■,u/ in isolation and in CVC syllables. The CVC utterances consisted of all combinations of seven initial consonants (/h,b,d,g,p,t,k/) and six final consonants (/b,d,g,p,t,k/). Formant frequencies for F1–F3 were measured every 5 ms during the vowel nucleus using an interactive editing tool. Results showed highly significant effects of phonetic environment. As with an earlier study of this type, particularly large shifts in formant patterns were seen for rounded vowels in alveolar environments [K. Stevens and A. House, J. Speech Hear. Res. 6, 111−128 (1963)]. Despite these context effects, large improvements in category separability were observed when a pattern classifier incorporated spectral change information. [Work supported by NIH.]
Acoustic differences between syllable-initial [f] and [θ]
Authors: Miller Marnie E. , Nittrouer Susan
Published: July 2002

The consonants [f] and [θ] are notoriously confusable in perception. Consistent with this fact, previous acoustic analyses have failed to demonstrate strong differences between syllables containing the two consonants in syllable-initial position. However, these earlier studies were limited in the numbers of speakers providing samples and in the measurements made. Therefore, five tokens of each of the syllables [f■], [fu], [θ■], and [θu] were recorded by each of eight speakers (four men and four women) and five acoustic properties measured in each syllable in the vicinity of the fricative segment: duration, amplitude, and first spectral moment of the fricative noise, and the frequency of the second and third formants at voicing onset. No consistent differences were observed for the noises themselves. Differences between syllables resided in the second and third formant transitions at voicing onset: frequencies of both formants are lower for [f] vowel than for [θ] vowel, both for males and females and for [■] and [u]. Thus acoustic evidence is provided supporting the perceptual result that the voiced formants provide whatever acoustic information is available for making phonetic judgments of these consonants. [Work supported by research Grant No. 5 R01 DC 00633 from the NIDCD/NIH.]
Categorical perception of Japanese moraic phonemes
Authors: Uchida Teruhisa
Published: July 2002

This study found that segment duration is perceived categorically in Japanese. Using a speech time-scale modification algorithm, PICOLA plus2, the nonword/kesonato/pronounced by a native Japanese male was manipulated to generate stimulus continua. The durations of /s/, /n/, /a/, and /t/ closure interval were manipulated in four continua. In the first experiment, three stimulus pairs, which had the same disparity in duration were selected from the short, long, and middle region of each continuum. Forty-eight randomized trials were presented to 20 native Japanese, who were asked individually to distinguish the difference of sounds by the ABX method. Pairs from the short and long regions of the continua were not accurately discriminated while pairs from the middle region were. In the second experiment, 44 stimuli were selected from every continuum. They were presented to the subjects for identification in Hiragana (Japanese characters). The second result demonstrated the existence of a moraic phoneme boundary paralleling the discrimination peak in the first experiment. This research concluded that native Japanese perceive the duration of relatively steady-static sounds categorically. And also, it is suggested that native Japanese utilize an automatic duration detection routine.
The effect of speaking-rate manipulations on segment durations and formant frequencies in dysarthric speakers with amyotrophic lateral sclerosis
Authors: Laures Jacqueline S. , Jeng Jing-Yi
Published: July 2002

The effect of speaking-rate manipulations on dysarthric speech is interesting from both theoretical and clinical perspectives. The purpose of the present study was to examine the influence of speaking-rate adjustments (conversational versus fast) on segment durations and vowel formant frequencies derived from sentence productions in speakers with amyotrophic lateral sclerosis (ALS), a disease that involves death of motor neurons serving the speech mechanism, with subsequent loss of muscle mass and strength. Speakers with ALS were clearly able to change their rate for the fast condition, though not in the same proportion as the control speakers. The segment durations responded to the rate manipulation in much the same way. For formant frequencies, the effect of rate was complex, but may be generally summarized as follows: F1 was affected systematically by the rate manipulation in control males, but not among the male subjects with ALS; for females in both groups, there was little effect of rate on F1. The effects of rate on F2 measures showed no clear trend, varying across vowels and groups. Results will be discussed relative to the speech production deficit in ALS and acoustic models of speech intelligibility. [Work supported by NIDCD Award DC00319.]
Synthetic aperture processing for underway noise ranging
Authors: Whitehouse Ian A.
Published: July 2002

In early 1992, Nautronix, participated in bidding for the Underway Radiated Noise Range (URNR) tender issued by the Royal Australian Navy (RAN). The tender document stipulated a radiated noise range capable of meeting the most stringent performance requirements. After assessing all of the bids the Commonwealth declined to award a contract on the basis that none of the submissions could demonstrate an adequate figure of merit. Nautronix subsequently proposed a ranging system employing synthetic aperture principles to achieve additional processing gain and reduce the complexity of the in-water system. With funding and assistance from the RAN the program has successfully progressed through a series of discrete phases to the development of the Shallow Acoustic Underway Range (SAUR), soon to be deployed at Thistle Island in South Australia. The range will fulfill all of the performance requirements of the original URNR, with the additional benefit of localization of sources on the vessel being ranged. SAUR will be used for ongoing RAN ranging activities. Both physical and synthetic arrays are employed. The presentation will discuss some of the requirements and performance capabilities of a synthetic array and present some of the results achieved during the development process and subsequent trials.
A tonpilz projector for use in an underwater horn
Authors: Moffett Mark B. , Powers James M. , Jevnager Michael D.
Published: July 2002

Tonpilz transducer head piston diameters are usually about one-half wavelength in diameter, so that ‘‘rho-c’’ radiation loading will be approximately achieved. However, for this underwater tracking application, the transducer is required to fit inside the throat of a 360-deg horn. The piston diameter is limited to 1 in., or about 0.22 wavelength at the resonance frequency, 13 kHz. The design is based on a lumped-element model. The PZT-8 ring stack is 2 in. long with an outer diameter of 0.5 in. and an inner diameter of 0.25 in. The head mass is 0.25-in.-thick aluminum, and the tail mass is tungsten, with a mass of 86 g. The transducer is isolated from its cylindrical housing with a syntactic foam spring. An O-ring piston seal is used, and a similar O-ring provides support for the tail mass. The results of free-field measurements will be presented and compared with the model, which will then be used to predict the performance after installation in the horn. [Work supported by Naval Air Systems Command.]
Temporal resolution of the dolphin’s hearing: Evoked-potential study
Authors: Supin Alexander Ya. , Popov Vladimir V.
Published: July 2002

Temporal resolution of the dolphin’s auditory system was studied using the auditory brain-stem-evoked response (ABR) recording in paradigms as follows: (i) paired click and pip stimulation; (ii) rhythmic click and pip stimulation; (iii) sinusoidally amplitude-modulated tones; (iv) noise burst of various duration (the temporal summation test); and (v) gap in noise detection. An integration temporal transfer function was derived from the data of all the listed experiments using a model of a linear integrator with subsequent nonlinear transform to ABR amplitude. All the experiments listed above gave strictly corresponding results. The integration transfer function consisted of an initial high-level part about 0.3-ms long and the subsequent low-level part with a decay of around 40 dB per time decade. The short initial part of the integration transfer function makes it possible to respond to paired stimuli with interstimulus intervals down to 0.2 ms, to follow rhythmic stimuli of a rate of more than 2000 Hz, and to detect gaps in noise as short as 0.1 ms. The subsequent low-level part is also important; it dictates response properties at interstimulus intervals and gap durations as loud as dozens of ms.
Temporary shift in delphinoid masked hearing thresholds
Authors: Ridgway Sam , Carder Don , Schlundt Carolyn , Kamolnick Tricia , Elsberry Wesley
Published: July 2002

Studies to determine the presence or absence of temporary shifts in masked hearing thresholds (TTS) in response to 1-s tones of 141–201 dB re: 1 μPa (S1 tones) were done at 3, 10, 20, and 75 kHz with four bottlenose dolphins and two white whales. Dolphins exhibited short-term changes in behavior above the following levels of S1 tones: 186 dB at 3 kHz, 180 dB at 10 kHz, 181 dB at 20 kHz, and 178 dB at 75 kHz. TTS levels were 194–201 dB at 3 kHz (two animals), 192–196 dB at 10 kHz (two animals), 193–196 dB at 20 kHz (two animals), and 192-194 dB at 75 kHz (two animals). One white whale exhibited no TTS at the highest level at 3 kHz while the other shifted at 198 dB. At 10 kHz the whales were in the upper range of the dolphins. The studies were completed without any harm to animal health or change in day to day behavior. [Work supported by the Office of Naval Research.]
Aerial and underwater hearing sensitivity of a northern elephant seal (Mirounga angustirostris)
Authors: Kastak David , Schusterman Ronald J.
Published: July 2002

Aerial (100 Hz to 28 kHz) and underwater (75 Hz to 59.8 kHz) sound detection thresholds were determined for a female northern elephant seal (Mirounga angustirostris) using behavioral psychophysical techniques. The resulting underwater audiogram shows a typical phocid pattern, with an upper frequency limit of about 59 kHz and relatively flat sensitivity from about 200 Hz to 30 kHz. In air, the elephant seal is 10–30 dB less sensitive than other phocid species tested. Underwater sound pressure thresholds averaged about 15 dB lower than aerial pressure thresholds. The degree of adaptation to underwater hearing in pinnipeds seems to follow phylogenetic trends; however, a high degree of aquatic specialization occurs in the northern elephant seal. Because the elephant seal is apparently nonvocal underwater, the most likely explanation for this high degree of aquatic hearing specialization lies in its ability to dive regularly to depths of 500–700 m. Although the elephant seal has poor aerial hearing relative to other pinnipeds, it has compensated for this deficiency by emitting very loud aerial vocalizations associated with seismic and visual signals to facilitate effective aerial communication. [Work supported by ONR.]
Could marine mammals use ambient noise imaging techniques?
Authors: Potter John R. , Taylor Elizabeth , Chitre Mandar
Published: July 2002

Ambient noise imaging (ANI) between 8–80 kHz has been demonstrated to produce good images at 40-m range using a 3-m aperture. With the two classic forms of sonar, active and passive, marine mammal biosonar has always outperformed man-made sonar of comparable dimensions. It is then natural to ask whether marine mammals may also use this newly discovered ANI technique as part of their sensory arsenal. Twenty odontecetes, for example, may find advantage in not broadcasting their imminent presence in pursuit of an intelligent prey. An odontecete has been observed successfully pursuing live prey without vision and with no echolocation clinks detected on any of several monitoring hydrophones during pursuit. This surprising observation may be explained if biological ANI is a viable option. To test this idea, an ANI simulation model has been adapted to include realistic target responses of fish with swimbladders, and a model of the receiving performance of a tursiops dolphin has been used to evaluate the possible performance envelope of a biological ANI system. It is found that it is plausible that some marine mammals use ANI to augment information from other senses at short ranges. The implications for understanding these animals and their behavior are substantial.
Improving loudspeaker performance for active noise control applications
Authors: Lane Steven A. , Clark Robert L.
Published: July 2002

Actuator performance is a critical part of active noise and acoustic control. The loudspeakers that are normally used as actuators in many active noise and acoustic control applications add significantly to the dynamics of the control loop and are detrimental to the controller’s performance. By compensating a loudspeaker with a technique similar to motional feedback, the loudspeaker performance is enhanced in applications such as control of acoustic enclosures. In this work, a method to easily and reliably compensate a loudspeaker in order to approximate constant volume velocity behavior over the piston-mode frequency range is presented and demonstrated. This reduces the influence of the environment upon the actuator, reduces low-frequency distortion of the speaker, and minimizes magnitude and phase shifts of the intended control signal. Numerical simulations and experimental results of the proposed methods are included. [Work supported in part by the Lord Corporation and the National Science Foundation under Grant No. CMS 95-01470.]
Analysis of mutual interaction on sonar array and vibration velocity measurement using NAH
Authors: Yokoyama Tomoki , Henmi Mitsuru , Hasegawa Akio , Kikuchi Toshiaki
Published: July 2002

Recently, sonar has tended to use lower frequencies and large output power to enhance its search distance. However, for such sonar, it is known that unpredictable deterioration of output and the destruction of specific elements may occur because of interference between elements. This research was conducted to analyze the interference between elements in an array in which the elements were driven by a regulated voltage—the influence of the mutual radiation impedance on the vibration velocity of the elements—using an equivalent circuit. The vibration velocity of each element was calculated using mechanical parameters for a practical array element. After that, the vibration velocity regulations of elements of (1,3) and (2,2) mode array caused by interactions were verified experimentally using a NAH imaging system which makes it possible to visualize fine regulations. These results are according to simulations.
Correlation of sound board normal modes with the radiated sound field of a grand piano
Authors: Hansen Uwe J. , Bork Ingolf
Published: July 2002

An extension of experimental modal analysis techniques enables the representation of the radiated sound field of a grand piano in reference to the phase of the excitation on the bridge. Sound field representations are illustrated for locations directly above and below the sound board and, in addition, in a plane directly in front of the instrument. The frequencies are chosen to coincide with the lower normal mode frequencies of the sound board, and the animated visual representations of the sound field are juxtaposed for comparison with modal analysis animations for the normal modes of the sound board.
Reproducing a piano performance
Authors: Litterst George F. , Bates Mike
Published: July 2002

There are many ways to store a piano performance for later reproduction, each of which lacks a complete and consistent definition. A composer typically notates a score for a pianist to play from—leaving many decisions to the whim of the performer. A pianist practices and commits hand and foot movements to memory—none of which produces a consistent result. A recording engineer captures the vibrations of sound for reproduction on a variety of playback systems—each of which plays back with individual characteristics which, from the listener’s point of view, depart significantly from the experience of the live performance. The Disklavier piano offers a different approach which is designed to capture and play back a performance accurately by recreating the original performance on an actual piano. The information which drives the disklavier can be output to a computer in order to display performance data and to facilitate an analysis of the performance.
Transmission of continuous and impulse noises to the fetus in utero
Authors: Gerhardt Kenneth J. , Abrams Robert M. , Huang Xinyan , Pierson Linda L.
Published: July 2002

Sounds which originate outside the abdomen of pregnant women reach the fetal inner ears after being filtered by the materials surrounding the fetal head and by its skull. In sheep, exogeneous sounds are low-pass filtered from 0.25 to 4.0 kHz at a rate of 6 dB/octave before reaching the head. There is little difference in sound pressures for low-frequency signals when recorded inside and outside the abdomen. The transmission route for fetal stimulation is via bone conduction with low-frequency sounds (<0.25 kHz) being attenuated by about 10 dB and higher-frequency sounds (0.5–2.0 kHz) attenuated by up to 45 dB. The amplitude and waveform of an impulse is influenced markedly by the location of the recording hydrophone within the uterus. Close to the intra-abdominal wall, the impulse is best characterized as a simple Friedlander wave (duration <1.0 ms) with a peak sound pressure level (pSPL) that is approximately 5 dB less than that recorded in air. With the hydrophone located deep inside the uterus, the pSPL is reduced by over 15 dB and the waveform resembles that of an impact with a decay time of greater than 12 ms. Fetal cochlear microphonic resembles the waveform of the impulse when it is recorded with a hydrophone located by the fetal head.
Calculation of the poroelastoacoustic response of a multilayered infinite planar porous material excited by acoustical and mechanical line sources
Authors: Rigobert Stéphane , Sgard Franck C.
Published: July 2002

Today, the prediction of the poroelastoacoustic response of multilayered porous media acoustically or mechanically excited for noise control applications, is of major concern in fields such as aeronautics, the automotive industry, building acoustics, or environmental acoustics. In this talk, a technique to evaluate the two-dimensional poroelastoacoustic response of a multilayered planar porous material due to both acoustical and mechanical line sources is presented. The technique based on a Fourier wave transform takes into account propagation phenomena into both the porous material skeleton and pores. Using the equations derived from the homogeneization theory for fluid-saturated porous media, propagation constants for the P1, P2 compressional wave and the S shear wave are determined. Applying boundary conditions at the media interfaces yields a linear system of equations in terms of reflection and transmission coefficients. This allows for the calculation of displacement amplitudes of the allowed wave motions in each medium. Numerical results showing the poroelastoacoustic responses (sound pressure level above the material, mean-square velocity of the skeleton at the air–porous interface, surface impedances) of several porous materials are presented in the case of both excitations.
Surface meteorology and animal communication
Authors: Larom David , Garstang Michael , Payne Katharine , Raspet Richard
Published: July 2002

Vertical temperature and wind gradients exert powerful and predictable influences on the area ensonified by animal vocalizations. Computer modeling of 15- and 30-Hz sound propagation in measured atmospheric conditions predicts that infrasonic African elephant calls can have ranges exceeding 10 km and will be highly directional in the presence of wind shear. The calling area is maximized under temperature inversions with low wind speeds. The calling area can expand and contract by an order of magnitude in 24 h. Topography, regional weather patterns, seasons, and climate variation modify this cycle. Similar influences affect the somewhat higher frequency calls of lions and may be a selective pressure toward their crepuscular and nocturnal calling behavior. Coyotes and wolves, which also live in areas with strong and prevalent nocturnal temperature inversions, show similar calling patterns, maximizing their chances of being heard over the longest possible distances. The pronounced dawn and evening vocalization peaks in other animals including birds, frogs, and insects may reflect the same influences, in combination with other factors which selectively limit high-frequency sound propagation. Atmospheric conditions therefore need to be taken into account in many studies of animal behavior. [Work supported by NSF Grant Nos. ATM92-07924 and ATM-9529315. Thanks to Peter Marler for useful comments.]
Fiber-optic sensors for structural–acoustic applications
Authors: Houston B. H. , Bucaro J. A.
Published: July 2002

Fiber-optic sensors under development for structural-acoustics applications will be discussed. These applications include the structural-acoustic monitoring and control of submarine and air-frame systems. In both cases, the ‘‘structure’’ is more or less cylindrical in shape, and the goal is to apply sensors to the structure, ideally, acoustic pressure and velocity sensors, but in some cases strain sensors, so as to be able to ‘‘know’’ through the application of suitable algorithms the exterior sound field (in the submarine case) or the interior noise field (for the air-frame system). In addition to the details of the particular fiber sensors, which have been successfully developed, a view will be presented as to what new and improved sensors are required for these applications. [Work supported by the Office of Naval Research.]
Allocation of hearing loss
Authors: Dobie Robert A.
Published: July 2002

In medical–legal evaluation of persons with hearing loss, allocation means the clinical process of estimating the relative contributions of different causes (noise, aging, etc.) or of different time periods. Allocation is not age correction; the practice of age correcting an audiogram prior to calculation of a hearing handicap score is fundamentally unfair. Allocation is an exercise of informed clinical judgment, requiring a solid understanding of the epidemiology of age-related and noise-induced hearing loss. While data specific to the individual, such as history, noise exposure measurements, and serial audiograms, should be given the greatest weight, quantitative methods based on epidemiological standards can also assist the clinician in making reasonable and unbiased allocation estimates.
Active structural acoustic control of a thin plate with a hybrid sandwich actuating mechanism
Authors: Lee Joshua T. , Meecham William
Published: July 2002

The objective of this research is to control the acoustic radiation of thin plates with hybrid active–passive actuating mechanisms. The hybrid mechanism consists of a piezoelectric actuator and viscoelastic and piezoelastic active constrained layers in a sandwich configuration, with the viscoelastic core layer in between the piezoelastic components. The actuator end of the hybrid mechanism is attached to a host structure. The main purpose of the proposed hybrid mechanism is to enhance the damping characteristics of the system while maintaining sufficient control authority. The damping characteristic of the hybrid mechanism is maximized by applying opposite voltages to the actuator and the active constrained layers, thus inducing a significant increase in shear strain within the viscoelastic layer. The general goal of this study is to evaluate the performance of the hybrid mechanism with some of the previously published actuating systems. Initial comparison results indicate that the proposed hybrid active–passive sandwich mechanism is more efficient than the actuating devices in comparison.
Is the dissipation induced by ‘‘fuzzy’’ substructures real or apparent?
Authors: Strasberg M.
Published: July 2002

There continues to be confusion whether the dissipation which can be induced in a master structure by a multitude of small attached substructures is ‘‘real’’ or only apparent. It is shown that the dissipation is real during steady-state vibration and can cause the master structure to have a larger loss factor than that of the substructures inducing the loss. The dissipation involves the continuous transfer of vibratory power from the master structure to the substructures and its continuous conversion into heat. During transient excitation, however, some of the initial dissipation in the master structure may be only ‘‘apparent,’’ involving the storing of some of the transferred power as vibratory energy in the substructures and its cyclical transfer back and forth between master and substructures until eventually dissipated, at a rate which in this case depends on the loss factors of the substructures. Examples of the two cases will be shown.
Effect of subglottal pressure variation in professional baritone singers’ voice source
Authors: Andersson Maria , Hultqvist Clara , Sundberg Johan
Published: July 2002

Subglottal pressure (Ps) is the main variable for control of vocal loudness. Measuring its effects on the glottal voice source is complicated, since independent variation of voice control variables is typically difficult for untrained subjects. Professional singers, however, can be assumed to have learned such independent variation. The voice source was analyzed by inverse filtering of the flow signal in five professional operatic baritone singers who, at three pitches, sang a string of [pV:] syllables while performing a diminuendo. Subglottal pressure was measured from the oral pressure during the [p] occlusion. From the flow glottograms the following parameters were determined: Qcl (closed quotient), dU/dt (negative peak amplitude of the differentiated flow glottogram), glottal leakage, ac flow (peak-to-peak flow amplitude), H1–H2 (level difference between the two lowest spectrum partials), and glottal compliance (ratio pulse airflow to subglottal pressure). In all subjects, the effect of Ps was similar and systematic for all parameters except glottal leakage. With decreasing Ps, ac flow and dU/dt decreased continuously while compliance increased and H1−H2 and Qcl, showing a strong negative correlation, saturated at about 5 dB and 0.5, respectively. The results will be compared to findings from earlier investigations of untrained voices.