bluuebunny/crossref_metadata_2025 huggingface dataset:
A wavelet method for estimating frequency-dependent damping in structures
Authors: Wilson Gary R.
Published: October 2005

Estimation of damping from the measurement of the vibrations or acoustic radiation of structures provides some insight into energy storage and dissipation mechanisms in the structure. Because damping is typically proportional to frequency, a method of estimating damping that scales with frequency is suggested. A wavelet approach has been taken to exploit the natural scaling properties of wavelets to estimate frequency-dependent damping. A wavelet transform, the damped complex exponential (DCE) transform, has been designed specifically for measuring damping [R. D. Priebe and G. R. Wilson, IEEE ICASSP 3, 205–208 (1994)]. This transform has been applied to stimulate impulse response frequencies to determine its accuracy and sensitivity to mismatch between the assumed damping/frequency ratio used by the wavelet transform and the actual damping/frequency ratio of the impulse response. It has also been applied to the measured impulse response of a fluid loaded thin elastic shell. Results of these measurements show reasonable agreement with theoretical predictions of damping.
Detection and characterization of blade–vortex interaction noise with wavelet analysis
Authors: Davis Wyatt O. , Pezeshki Charles , Mosher Marianne
Published: October 2005

A discrete implementation of the wavelet transform (WT) was used to analyze blade–vortex interaction (BVI) noise in acoustic helicopter noise signals. A BVI detection algorithm was developed which takes advantage of the prominence of BVI noise in certain subbands. Isolated-BVI signals were constructed by detecting impulsive BVI events and extracting them from the subbands. Four metrics were tested for suitability as BVI estimators. Two of these, the rms levels of the isolated-BVI signals and a metric computed from the A-weighted frequency spectra of the isolated-BVI signals, were seen to characterize BVI noise severity, but were computationally expensive. The other two metrics were computed from the amplitudes of the BVI events in the subbands. The first, based on the exponential behavior of the amplitudes across subbands, failed to characterize BVI noise severity for certain signals and was highly sensitive to noise. The second, computed from the amplitudes of BVI events in a single subband, was an effective BVI estimator and was relatively insensitive to noise. This estimator is especially convenient because it is easily used as a decision threshold in the detection algorithm, thereby making possible simultaneous BVI detection and characterization.
Audio compression based on sine-crossing representations of signals
Authors: Hilton Michael L. , Panda Prasanjit
Published: October 2005

The sampling theorem of Bar-David [J. Bar-David, Info. Control 24, 36–44 (1974)] provides an implicit representation of bandlimited signals using their crossings with a sine function. This sine function is chosen in a way that guarantees a unique representation of the signal. On a finite signal, this leads to a multiplicative representation involving a Riesz product whose roots form the representation of the original signal. These roots can be encoded to provide high-quality, near lossless audio compression. The sine crossing representation can also be combined with the wavelet transform to provide further compression. [Work supported by ONR.]
Binaural profile analysis: On the comparison of interaural time difference and interaural correlation across frequency
Authors: Woods William S. , Brughera Andrew R. , Colburn H. Steven
Published: October 2005

Experiments are reported on that were aimed at determining if a ‘‘profile-analysis’’ process is performed in the binaural domain, specifically with interaural time difference (ITD) and interaural correlation (IC). Sensitivity to variations in these parameters across frequency was investigated by roving the parameters across intervals and requesting subjects to choose the interval containing an incrementally different parameter value in a target band. The size of the increment needed to identify the target interval was measured for several bandwidths of the total stimulus. In the ITD experiments, tone complexes were used and the target was a tone at 500 Hz. For harmonic complexes (100-Hz spacing), the addition of reference tones (out to 4 kHz) does not aid detection of the target interval but usually degrades performance. For logarithmic complexes (spacing factor 1.3) performance improved at the widest (4 kHz) bandwidth. In the IC experiment, spectrally continuous noise was used, with a 115-Hz wide target band at 500 Hz. Adding fringe bands increased thresholds significantly for a narrow stimulus bandwidth (354 Hz), and performance returned to that measured for the target alone for wide bandwidths. These results are discussed in terms of possible binaural contributions to auditory grouping. [Work supported by NIDCD (Grant DC00100).]
Interaural phase locking as a function of interaural level
Authors: Green G. G. R. , Rees A. , Henning G. B.
Published: October 2005

Sinusoidal phase modulation in a sinusoidal carrier was monaurally presented to observers’ left ears in standard two-interval forced-choice experiments: The carrier was phase modulated in one of two randomly chosen observation intervals and the observers were required to indicated the interval having phase modulation. In the dichotic condition, a pure tone with the same frequency (500 Hz) and level (70 dB SPL) as the carrier was presented to the right ear in both observation intervals; in the monaural condition, the pure tone was attenuated by 71 dB. The 1.5-s stimuli were gated simultaneously with 20-ms Gaussian rise/fall times. At low modulation rates, the depth of phase modulation corresponding to 75% correct responses in the dichotic condition was an order of magnitude smaller than in the corresponding monaural condition consistent with the results of G. G. R. Green, J. S. Heffer, and D. A. Ross [J. Physiol. (London) 260, 49P–50P (1976)]. The dichotic advantage is scarcely affected by two orders of magnitude reduction in the level of the pure tone in the right ear. The results are related to the precision of phase locking in the auditory system. [Work supported by the Royal Society.]
The exact sonar cross section of an elastic spherical shell near the sea surface
Authors: Huang H. , Gaunaurd G. C.
Published: October 2005

The acoustic scattering by a submerged spherical elastic shell near a free surface and insonified by plane waves at arbitrary angles of incidence is analyzed in an exact fashion by the classical separation of variables method. To satisfy the boundary conditions at the free sea surface, as well as on the surfaces of the elastic shell, the mathematical problem is formulated using the method of images. The scattered wave fields are expanded in terms of spherical wave functions using the addition theorems. The final results come out in terms of Wigner 3-j symbols or Clebsch–Gordan coefficients. Quite similar to the problem of scattering by multiple spheres, the computation of the scattered pressure field involves the solution of an ill-conditioned complex matrix system, of size that depends on the number of terms in the modal series required for convergence. This, in turn, depends on the value of the frequency and on the proximity of the steel shell to the free surface. The matrix equation is solved by the Gauss–Seidel method. Many backscattered echoes from the shell are computed, and its form function is displayed for various depths and in broad frequency intervals. The plots show that the large-amplitude, low-frequency resonance features in the sonar cross-sections shift upward as the shell approaches the free surface. This can be attributed to the decrease of added mass for the shell vibration. [Work partially supported by the Independent Research Program of the CDNSWC.]
Diffraction analyses with and without flow: A unifying spectral approach
Authors: Martinez R.
Published: October 2005

This paper discusses sample diffraction problems from the fields of structural acoustics in a still medium and of aeroacoustics at high subsonic Mach numbers. Respectively and specifically: Diffraction by a tandem arrangement of thin circular plates of finite radius and inertia, and scattering of high-frequency rotor/stator noise by the nacelle of a modern aeroengine. The presence of a freestream endows the elemental diffraction loads in the second class of problems with the capacity to inject vorticity into the medium. The need to account for it has classically prompted the development of a new mathematical interpretation of scattering, called ‘‘unsteady aerodynamics,’’ so that flow and flowless diffraction communities have tended to work in mutual isolation. A side objective of this paper is to speak to both groups by presenting a completely formal complex-contour representation of the fundamental lift kernel for the flow case. That spectral formulation displays the role of vorticity explicitly through an additional singularity that shifts away to complex infinity as the flow is turned off. The remaining spectrum is the Fourier transform of the hypersingular diffraction kernel of ordinary acoustics.
Generalized holography for imaging elastic structures
Authors: Porter Robert P. , Rouseff Daniel , Bennink David
Published: October 2005

Generalized holography is a technique for determining the properties of acoustical sources or scatterers [R. P. Porter, ProgressinOptics 27, 1989]. In its most general form, the radiating or scattered field and its normal derivative are measured on a recording surface of arbitrary shape. The resulting measurements can be forward propagated into the far field to calculate the radiation pattern. The field can also be backpropagated toward the original source location to generate an image. For the special case of a closed recording surface surrounding the source, the image is independent of the shape of the hologram. Moreover, the image will be independent of evanescent (subsonic) components of the field even when the measurements are made in the near field. This is an important consideration for locating sources of radiation on an object. In this talk, generalized holography is applied to simple elastic structures to determine the modes of vibration. Numerical results will be presented for spherical shells excited by localized surface pressure or by an incident pressure wave.
Individual differences in speech and nonspeech processing among normal-hearing subjects
Authors: Surprenant Aimee M. , Watson Charles S.
Published: October 2005

While a large portion of the variance among listeners in auditory speech processing is associated with the audibility of components of the speech waveform, it is not possible to predict individual differences in speech perception strictly from the audiogram. Psychoacoustic measures of spectral-temporal acuity with nonspeech stimuli also have been shown to correlate only weakly (or not at all) with speech processing. In a replication and extension of an earlier study (Watson etal., J. Acoust. Soc. Am. Suppl. 1 71, S73) 100 normal-hearing college students were tested on speech perception tasks (nonsense syllables, words, sentences in a noise background) and on 6 spectral-temporal discrimination tasks using simple and complex nonspeech sounds. Factor analysis showed that the abilities that explain performance on the nonspeech tasks are quite distinct from those that account for performance on the four speech tasks. Performance was significantly correlated among speech tasks, and among nonspeech tasks. Either, (a) auditory spectral-temporal acuity for nonspeech sounds is orthogonal to speech processing abilities, OR (b) we have yet to identify the appropriate task or types of nonspeech stimuli that exercise the abilities required for speech recognition. [Work supported grants from NIH and AFOSR to Indiana University.]
Temporal integration of loudness as a function of level
Authors: Florentine Mary , Buus So/ren , Poulsen Torben
Published: October 2005

This study compared temporal integration of loudness for 1-kHz tones and broadband noises. Absolute thresholds and levels required to produce equal loudness were measured for 5-, 30-, and 200-ms stimuli using adaptive, two-interval, two-alternative forced-choice procedures. Levels ranged from 5 to 80 dB SL for noises and from 5 to 90 dB SL for tones. Results for 6 listeners with normal hearing show that the amount of temporal integration, defined as the level difference between equally loud 5- and 200-ms stimuli, varies nonmonotonically with level. The average amount of temporal integration varies from about 10–12 dB near threshold, to a peak of 18–19 dB when the 5-ms tone is about 56 dB and the 5-ms noise is about 76 dB SPL; at higher levels, the amount of temporal integration decreases to 10 dB for tones and 13 dB for noises with levels around 100 dB SPL. These results indicate that modified power functions cannot account for the growth of loudness for tones at all durations. They also indicate that the growth of loudness may, at least in part, be consistent with the nonlinear input/output function of the basilar membrane. [Work supported by NIH-NIDCD R01DC02241.]
The role of auditory cues in assisting pursuit motor functions
Authors: Villacorte Renato G. , Perrott David R. , Ferguson Debra L.
Published: October 2005

Eight experienced subjects were used in a two-alternative, forced-choice visual search paradigm in order to investigate the auditory system’s contribution in maintaining pursuit eye movements after the cue that indicated the target’s location, velocity, and direction of travel was removed. Subjects were instructed to use the target motion information provided by the cue to anticipate the location of the target onset after the delay following the cue’s offset. Predictably, conditions that included visual target information produced faster RT’s than a cue consisting of only auditory information. Performance also declined when the velocity of the target or the duration of the delay was increased. These results may suggest the importance of information retention in maintaining pursuit tasks when target information is removed. The importance of the auditory system in processing spatial information for pursuit movement tasks will be discussed. [Work supported by NSF.]
Active control of aircraft cabin noise
Authors: Mathur Gopal P.
Published: October 2005

Aircraft cabin noise control in the past has relief heavily on improving sidewall attenuation by passive ‘‘add-on’’ treatments. The conventional passive methods, such as adding mass, damping, or acoustic absorption, etc., not only impose a stiff weight penalty, they are also ineffective in improving the low-frequency sound transmission loss of an aircraft fuselage sidewall. Active control of sound inside aircraft cabins has been the focus of research in recent years and has shown considerable promise. Laboratory and in-flight tests of prototype active control systems for tonal noise reduction using secondary speakers have demonstrated the feasibility of active noise control (ANC) in aircraft cabins. In recent years active structural acoustic control (ASAC) has also been applied to aircraft fuselage structures in controlling low- to mid-frequency structural sound radiation. In the ASAC technique, control forces are applied directly to the vibrating structure by actuators (such as piezoelectric transducers) instead of using loudspeakers to minimize the radiated sound field. The ASAC approach is also important in the design of ‘‘smart structures,’’ which incorporate both sensors and actuators in the structure for noise and vibration control. This paper presents results of investigations (conducted at McDonnell Douglas) of application of both ANC and ASAC techniques to a full scale aircraft fuselage. Significant sound pressure reductions were achieved throughout the cabin for multiple tonal frequencies of excitation. The performance of the ASAC method is compared with that of the ANC system using speakers. The flight test results with a prototype ANC system in an MD-80 aircraft will also be presented.
Feedback-stabilized artificial bedrock: A practical implementation of a passive/active vibration isolation system
Authors: Beard A. M. , Schubert D. W. , von Flotow A. H.
Published: October 2005

Active control in the presence of resonant structural dynamics is challenging since such dynamics are both uncertain and easy to destabilize. This is particularly true when broadband control is required. Active vibration isolation is plagued by such difficulties. In spite of much development work, few systems are in service and these remain very sensitive to structural resonances. For each such system, the control logic is fine-tuned during installation. When the system’s environment changes (sometimes only slightly), unstable behavior is common. This presentation describes basic options in passive/active vibration isolation and highlights mechanical architectures which make robust active control possible. Simple theoretical arguments are supported with experimental evidence. The presentation concludes with a detailed description of a recently developed system which is based upon one such mechanical architecture; Barry Controls’ STACIS-2000. This system uses seismic motion sensors (geophones) and piezo-ceramic stack actuators to create feedback-stabilized ‘‘artificial bedrock.’’ Vibration-sensitive payloads are mounted to these stiff, quiet points. The system delivers the isolation performance of a well-damped 0.3-Hz passive mount and the stiffness (to inertial space) of a 25-Hz mount. The system is robust to the dynamics of both the vibration source and the receiver.
Implementation of fast transversal filters for active structural acoustic control
Authors: Bronzel Marcus J. , Fuller Christopher R.
Published: October 2005

The design of an optimal feedforward controller in active noise control applications for controlling the sound radiation from a vibrating structure can be seen as a system identification problem. Most control implementations use a stochastic gradient search algorithm to adaptively identify the impulse response of the optimal control filter. The convergence properties of the widely used filtered-x LMS algorithm depend on the signal properties of the filtered reference signals. Sensing the reference signals from the vibrating structure is inevitable in most real applications and will effectively result in structural filtering of the unknown noise source. The filtered reference signals from a structural sensor generally exhibit a large eigenvalue spread resulting in poor convergence properties of the adaptive controller. A new extended-filtered-x approach has been developed which makes the implementation of fast RLS type algorithms possible. These algorithms are based on an orthogonal projection of the predictor error into the subspace of the filtered reference signals and therefore converge independent from the underlying signal statistics. Experiments for active control of noise from a vibrating plate have been conducted which demonstrate the superior control performance of fast transversal filters.
Normalized stochastic gradient method for nonstationary environment
Authors: Lee K. , Shin Jung G.
Published: October 2005

The normalized least-mean-squares (NLMS) method has been adopted for a wide range of adaptive filter applications due to its simple structure and low complexity of computation. However, under certain circumstances, the convergence rate may not be satisfactory. The performance may even be poorer under certain nonstationary situations. A new normalized stochastic gradient (NSG) method is suggested to overcome the drawbacks of the NLMS method. The main features of the NSG method are (1) the time varying convergence parameter and (2) the onset detection. While in the NLMS method the convergence parameter is fixed, it is a function of time in the NSG method. It is selected to minimize the conditional variance of the filter coefficients at the next step given a set of the previous coefficients. The time-varying sequence of the convergence parameter makes the NSG method converge fast. The new NSG method has the capability of the onset detection. It detects the statistical changes of the desired input and by resetting the adaptive procedure it keeps tracking the changed signal. The simulations show that the new NSG method outperforms the NLMS method under both stationary and nonstationary environments. [Work supported by Daewoo Motot Company, Seoul, Korea.]
Pitch perception based on a temporal energy rate model
Authors: Reetz Henning
Published: October 2005

Theories about the mechanisms of human’s pitch perception either are based on the temporal firing rate of the haircells in the basilar membrane or on the place of these cells in the membrane in a sort of spectral representation. The insensitivity to the phase of individual components of a complex signal and the ability to perceive pitch for binaural presented harmonics has given experimental evidence for place-based pitch perception models. This paper explains theses findings with an alternative temporal rate model. The proposed explanation is based on a model of the inner ear that computes the energy of an acoustic signal in the time domain, leading to a temporal energy distribution of the signal. This temporal energy distribution is converted by a simple decision logic to a pitch value. The model will be theoretically discussed, reanalyses of reported experimental findings are presented, new experimental evidence for the proposed model will be given, and a computer program to determine the pitch of a speech signal based on the model’s principles will be evaluated.
Difference limens for roved glides
Authors: Madden John P.
Published: October 2005

The study determined glide difference limens (GDLs) for up-glides in several conditions and estimated how well a level-detection model of the auditory periphery could account for the data. Signal durations were 50, 100, and 200 ms, and the average stimulus center frequencies were 1 and 4 kHz. To avoid the confounding effect of between-stimuli static pitch cues, the center frequencies of the standard and target stimuli were ‘‘roved’’ about the center frequencies [Neill and Feth, J. Acoust. Soc. Am. Suppl. 1 87, S23 (1990)]. The standard signals increased in frequency by 0, 200, and 400 Hz. The subject’s task was to distinguish between the standard and a target signal with a greater increase in frequency in a 2-alternative, forced-choice task. The increase in the target signal was varied adaptively until discrimination threshold was obtained. The results for the 0-Hz standard were consistent with previous findings that the change in Hz at threshold is constant across duration in a glide-detection task. The results for the 200 and 400 Hz standards extend this finding to a glide-discrimination task. The modeling results suggest that the auditory system tracks gliding signals by monitoring the change in level of the output of the auditory filters. [Work supported by NIDCD.]
Pitch-level functions for pure tones in the presence of partial masking
Authors: Burns Edward M.
Published: October 2005

The purpose of this experiment was to determine if the pitch changes of pure tones with changes in level are dependent on the spread of excitation with increasing level. Pitch-level functions were obtained in quiet, and in the presence of band-reject masking noise, for frequencies ranging from 250 to 8000 Hz. Both the spectrum level of the masking noise and the width of the the band-reject region surrounding the pure tones were parametrically varied. In addition, estimates of the amount of partial masking for each condition were obtained from loudness matches. Preliminary results suggest that, for levels above 60 dB SPL, the pitch shifts associated with partial masking usually reduce or eliminate pitch changes with level. [Work supported by NIDCD and the Virginia Merrill Bloedel Hearing Research Center.]
On the perceptual asymmetry in frequency modulation discrimination
Authors: Zhang Tao , Feth Lawrence L. , Krishnamurthy Ashok K.
Published: October 2005

Several researchers have observed perceptual asymmetry in frequency modulation discrimination experiments. Porter etal. (1991) found that when listening to a formant transition followed by a frequency plateau, listeners detected the onset frequency much better for the falling transition than for the rising transition. Demany and McAnally (1994) discovered that the frequency difference limen measured at frequency maxima of a 5-Hz cosine frequency modulation is significantly smaller than at frequency minima. Heil etal. (1992) also observed asymmetry in the FM response in chick auditory cortex. They proposed that this effect was due to the asymmetrical lateral inhibition in the unit. Preliminary results in this lab indicated that this perceptual asymmetry also exists when listeners were asked to discriminate between a sinusoidal plus linear ramp frequency modulation (SLRFM) and a linear ramp frequency modulation (LRFM) (Zhang etal., 1994). In this presentation, perceptual asymmetry is systematically studied for both rising and falling LRFMs. The effect of starting phase of a SLRFM signal is also examined. The experimental results are discussed in terms of existing modulation models and physiological explanations. [Work supported by AFOSR.]
Underwater linear horn array simulator
Authors: Butler Stephen C. , Hughes W. Jack
Published: October 2005

Sonar transducers with a radiating face smaller than one half wavelength tend to have a low radiation impedance load and consequently a narrow transmitting bandwidth. Thus, when the transducer is tested alone, the measured results yield a poor representation of its intended array performance. The objective of this research was to develop a fluid means to ‘‘ρc’’ load a single sonar transducer element by imposing a condition similar to its intended use in an array. A new method which accomplishes this and attains ‘‘ρc’’ loading utilizes a linear endfired waveguide, which forces a single transducer to behave as if it were in an array under ‘‘ρc’’ loading conditions. This is accomplished by an ‘‘underwater linear horn array simulator’’ which is composed of a rigid-walled cylindrical tube with slots of equal area equally spaced along the length of the tube. Acoustical circuit theory shows that 85% ρc loading over an octave bandwidth would be achieved. Measurements on a physical model confirm the prediction. Measured mechanical Q’s of the sonar transducer without the horn is 7.5, and with horn is 5, showing that the loading effects of the horn have been achieved. [Work supported by ONR and NUWC, New London, CT.]
Acoustic detection of jet aircraft
Authors: Ferguson Brian G.
Published: October 2005

A passive broadband acoustic technique is described that detects the transit of a subsonic jet aircraft. The outputs from a pair of spatially separated microphones are cross-correlated in three overlapping frequency bands. The time lag that corresponds to the maximum value of the cross-correlogram is extracted for each of the three bands every second. Coincidence detection of this time lag information results in the detection of the jet transit with a negligible false alarm rate. The detection range is extended by applying the technique to the beamformed outputs from a pair of microphone arrays. The results of applying the technique to real data from 25 jet transits are presented.
Near-field acoustic holography for enclosures with unknown Green’s functions
Authors: Kay Kelly Q. , Fuller Chris R. , Lyle Karen H.
Published: October 2005

A method for predicting the acoustic field in acoustically complex cavities is developed based upon current near-field acoustic holography (NAH) techniques. Current NAH methods make use of analytical Green’s functions to generate predictions of global acoustic fields. For this reason, NAH is easily applied to generate predictions in free fields, and in cavities with simple geometries and uniform boundary impedances. For acoustically complex cavities, however, the absence of a known analytical Green’s function, renders current NAH methods either not solvable, or in cases where approximate Green’s functions are used, not accurate. The method requires no prior knowledge of the acoustically complex cavity’s Green’s function. As well, no approximations about the boundary conditions are required. Instead, the method takes advantage of the discrete nature of NAH predictions, in conjunction with an initial measurement of a cavities acoustic pressure field, to generate a cavity specific discrete Green’s function. Computational and experimental results will be presented along with a detailed explanation of the method. [Work supported by NASA Langley Research Center.]
Attenuation of broadband noise in a reverberant room using a multichannel active noise control system
Authors: Guthart Gary S. , Nowlin William C. , Toth Gregory K.
Published: October 2005

Active noise control (ANC) is often discussed in the context of reducing noise in vehicles. The acoustic reverberation of typical vehicle cabins makes the application of ANC to quieting interior noise a stiff challenge. While some ANC approaches take advantage of the modal structure of reverberant enclosures to provide reduction throughout the enclosure, these approaches become infeasible for many frequency bands of practical interest because of increasing modal density with increasing frequency. For high-bandwidth, diffuse fields, noise reduction is achieved locally by specifying a quiet zone within the enclosure. Experimental results for broadband, local quieting in a diffuse field using a multichannel ANC system are presented. The reverberant enclosure is an ordinary room, measuring approximately 1.4 m×2.4 m×2.4 m and containing a seated operator with six microphones defining the quiet zone near the operator’s ears. The control system uses a single reference signal and two error channels to drive four control speakers. An average of 20-dB reduction in sound pressure level is found at the quiet-zone microphones for the frequency range 50 to 1000 Hz. These results demonstrate the viability of real-time, multichannel ANC for locally attenuating random noise in diffuse acoustic fields.
Effects of atmospheric stratification on sonic-boom propagation
Authors: Cleveland Robin O.
Published: October 2005

Sonic-boom propagation is affected by stratification, geometrical spreading, nonlinear distortion, absorption and dispersion, and turbulence. Stressed in this paper is stratification, in particular its indirect effect on distortion and absorption. The stratification of the density and sound speed leads to refraction and impedance variation, which play a major role in determining the amplitude of the waveform on the ground. Stratification, and associated spreading, can also control the amount of nonlinear distortion a sonic boom suffers. In extreme cases the amount of nonlinear distortion is finite—a phenomenon known as waveform freezing. Analysis shows that for aircraft in the lower 20 km of the atmosphere waveform freezing does not occur. Through their dependence on temperature, pressure, and humidity, absorption and dispersion are also stratified. A new time domain algorithm, based on a Burgers-type equation, was developed to analyze the effect of the stratification of absorption [ 3275 (A) (1994)]. The code is used to predict sonic-boom waveforms on the ground. It is demonstrated that sonic-boom shocks are affected not just by local absorption but also by absorption along path for the past 5 km or so. [Work supported by NASA.]
Effects of sonic booms on animals: Past history and future directions
Authors: Bowles Ann E.
Published: October 2005

Models developed to describe and mitigate damage to human hearing after sonic-boom exposure can be applied to a wide range of species. If humans and laboratory animals are poor models for a species of concern, or if intense focused sonic booms are anticipated, experimental assessments will be needed. Although attenuation across interfaces (air–water and air–soil) will protect many aquatic and fossorial species, attenuation may not protect individuals near the interface if boundary phenomena like evanescent energy are found to be important. Panic reactions are a likelier hazard for animals, at least in air. Damage in panics is predicted best by species-typical avoidance behaviors (e.g., panic flight), sound exposure level (after appropriate weighting), and previous experience with impulsive man-made noise. Dose-effect models have not been developed because controlled experimental studies with booms at levels up to 150 dB (peak flat SPL) have failed to elicit panics. However, widespread concern continues because there are circumstantial accounts of catastrophic damages, notably the ‘‘Sooty Tern Incident.’’ Controlled studies of habituation using initially naive animals are needed to develop dose-effect models for damaging responses. Effects of impulse-induced frights on (1) gametogenesis, conception, and early embryonic development, (2) parental care, (3) activity, and (4) habitat use should be investigated as well.
Perception of voice-onset-time cued by articulatory information
Authors: Williams David R.
Published: October 2005

This paper presents results of a first perceptual assessment of VOT continua synthesized using articulatory rather than acoustic parameters. The research employed Sensimetrics’ HLSYN synthesis system, which embodies an articulo-acoustic model of speech production [K. N. Stevens and C. A. Bickley, J. Phon. 19, 161–174 (1991)]. The system permits time-varying control of fundamental frequency, vocal-tract shape, and of glottal, oral, and nasal orifice sizes; calculated aerodynamic quantities provide the basis for estimating KLSYN88 synthesizer source parameters. Six 10-member VOT continua (/ba/–/pa/, /da/–/ta/, /ga/–/ka/, /bi/–/pi/, /di/–/ti/, /gi/–/ki/) were constructed by varying the glottal adduction trajectory so that voicing onset occurred 0, 15, 30, ..., or 135 ms after oral release. In addition, two peak glottal openings (18, 30 mm2) were tested; for /a/, rate of oral release was also varied (slow, fast). Subjects rated the ‘‘goodness’’ of the CVs as exemplars of the appropriate voiceless stop on a ten-point scale. In general, subjects preferred longer VOTs for velars than for labials. For alveolars, longer VOTs were preferred before /i/ than before /a/. Effects of peak glottal opening and oral release rate on VOT preferences were negligible. The results are discussed relative to traditional findings for acoustically defined VOT continua. [Work supported by NIMH.]
Basin-scale tomography in the western Mediterranean
Authors: Send Uwe
Published: October 2005

An international acoustic tomography experiment had been deployed in the western Mediterranean from January to October 1994. Seven transceivers spanned the region between France, Algeria, the Balearic Islands, and Sardinia/Corsica. The basin (maximum range 600 km) was ‘‘illuminated’’ by a single HLF-5 source, the remaining sources had a shorter range but could communicate with their neighbors. Extensive hydrographic measurements and analysis of historical data accompanied the observations, including a large-scale survey during deployment and recovery and a 2-weekly XBT section along the main transmission path. Some paths went along/through complicated topography, and in addition a shipboard acoustic survey was carried out to study the propagation into shallow water. All instruments remained operational for the entire period, and 6 of the 7 had 100% return of received data. The receptions show a high S/N ratio with well-resolved arrivals that agree well with acoustic propagation predictions. The seasonal variation of the travel times appears to be a good measure of the cycle of the large-scale heat content. The 3-D basin-averaged temperature is estimated to have an accuracy of 3%–4% of the seasonal amplitude. A system like this, installed with shore-cabled instruments, should be a valuable tool for monitoring interannual and climate-scale water mass variability.
Acoustic travel time biases caused by mesoscale eddy
Authors: Shang E. C. , Wang Y. Y. , Voronovich A. G.
Published: October 2005

Smaller scale fluctuations can be smooth-out by taking a long range propagation under linearized assumption. But the nonlinearity of the equations relating ocean perturbations to acoustic travel times leads to a bias if the problem is linearized about a range-independent reference state. The travel time tRD in the range-dependent channel differs from the travel time tRA through the range-averaged channel. In ray theoretical regime, a warm bias (tRD<tRA) has been found for mesoscale eddy in general. In this paper, numerical simulation of modal travel time shows that there is a ‘‘cold’’ bias (tRD≳tRA) caused by mesoscale eddy in mode theory regime. [Work supported by ONR, ARPA, and NOAA.]
Design of a miniature fiber optic acoustic sensor for an acoustic viscometer
Authors: Guevara José D. , Raichel Daniel R.
Published: October 2005

An acoustic fiber optic sensor was designed for the miniature version of an acoustic viscometer under development at The Cooper Union Acoustic Research Center. The sensor consists of a single mode fiber optic cable embedded in the center of a 50-mm×50-mm×5 mm compliant polymer layer. It was noted that the geometrical versatility of the sensor could be minimized further, allowing for shorter lengths of sensitized fiber without sacrificing acoustical sensitivity. A Mach–Zender interferometric system is employed to detect the phase shift of the modulated optical signal in the sensitized fiber. A flat frequency response in the 200 Hz to 20 kHz was predicted. The length of the fiber determines the minimum value of detectable pressure. In addition to immersion in water the sensor has the potential to also withstand immersion in mildly acidic and alkaline solutions.
Scattering from a fluid-loaded elastic spherical shell in proximity to a rough fluid–elastic interface: Numerical results
Authors: Smith Judy , Bishop Garner C.
Published: October 2005

A null field T-matrix formalism is developed and used to calculate scattering of a pressure wave from a fluid-loaded elastic spherical shell in proximity to a rough fluid–elastic interface. The Helmholtz–Kirchhoff integral representations of the various scattered pressure and displacement fields are constructed. The surface fields are required to satisfy the elastic boundary conditions and the scattered fields are required to satisfy the extended boundary condition. The free-field T matrices for the elastic shell and the rough fluid–elastic interface are constructed and used in the Helmholtz–Kirchhoff and the null field equations for the shell-interface system. It is shown that the T matrix for the system is simply related to the free-field T matrices for the shell and the rough fluid–elastic interface. A perturbative solution is obtained for scattering from arbitrary roughness, and an ‘‘exact’’ solution is obtained for scattering from periodic roughness. The ‘‘exact’’ solution is used to obtain a variety of numerical results that show some of the effects of the acoustic coupling that occurs between the rough interface and the elastic spherical shell.
Pressure impulse response measurements for elastic scatterers in water and regulation of the source spectrum
Authors: Marston Philip L. , Morse Scott F.
Published: October 2005

A large PVDF sheet adjacent to the scatterer has been used to excite the plane-wave pressure impulse response of elastic shells over a wide spectral range [Kaduchak etal., to be published in J. Acoust. Soc. Am. (1995)]. Since the sheet is transparent to the scattered signal, the receiver hydrophone may be on the opposite side of the sheet. The understanding and control of the spectrum of the radiated pressure pulse is useful for facilitating the detection of specific target spectral features. An idealized circuit model is examined where the sheet is excited by a step voltage source having a real impedance given by the resistance R. Let C denote the sheet capacitance and let the step occur at t=0. The radiated pressure for a thin sheet becomes a step followed by an exponential tail: exp(−t/RC). The magnitude spectrum is proportional to [1+(ωRC) 2]−1/2. Increasing R reduces the high-frequency content which may be advantageous for certain measurements. Applications include the impulse excitation of low-frequency structural resonances of shells in water. Adjacent modes exhibit a prominent beating in the response. [Work supported by the Office of Naval Research.]
Locally reacting boundary condition over sloping boundaries for the parabolic equation
Authors: Tollison B. G. , Robertson J. S. , Siegmann W. L.
Published: October 2005

A boundary condition which models locally reacting boundaries is derived for the generalized parabolic equation. This formulation is valid over nonhorizontal boundary surfaces. The derived condition is discretized using Lagrange polynomials. Particular implementation schemes are discussed for nonhorizontal boundaries. Numerical results compare the accuracy of this approach with other methods that have been used with the PE. Comparison with experimental results may also be presented. [Work supported by ONR and USACECOM.]
Adult attribution of the infant vocalizations
Authors: Shimura Yoko , Imaizumi Satoshi
Published: October 2005

Adult attribution of the infant vocalizations was investigated by perceptual rating experiments for 717 voice samples recorded from seven infants at 2, 6, 9, 12, and 17 months of age. Perceptual rating was performed using nine vocalization- and emotion-related reference words by 15 normal heating adult listeners. By a principal factor analysis, three factors representing the emotional contrast of crying/frightened/sad versus laughing/pleased/happy, shout/surprising versus secret-talk/calm, and speaking versus singing were studied. Even at 2 months of age, significant individual differences were observed in the extracted factor scores, although three were less variability compared to those obtained from the elder infants’ vocalizations. These results suggest that the ability to express emotion through vocalization seems to be developing during the observed months of age, although infants even at 2 months of age can express some aspects of emotion through vocalization.
Speaker normalization for tone
Authors: Moore Corinne B.
Published: October 2005

Segments with identical acoustic characteristics may not be perceived identically, because listeners normalize for acoustic variability due to vocal tract differences among speakers. While normalization studies have been done for vowel perception, the present experiment uses Mandarin Chinese to investigate speaker normalization for lexical tones. In this study, two speakers were identified for whom the low tone (tone 3) of the high- pitched speaker occurred in the same F0 region as the midrising tone (tone 2) of the low-pitched speaker. Synthetic syllables formed three continua used in a series of perception tests. The three continua varied along either F0, timing of the turning point, or both acoustic dimensions. Stimuli were placed after a natural precursor from each of the two speakers. Test items were randomized and presented in a mixed block condition. Results show that category boundaries shift contrastively in the direction predicted; that is, the same stimuli were perceived differently in the two precursor conditions, although only for stimuli varying along the F0 and both F0 and turning point dimension, but not for stimuli varying along the duration dimension (turning point) alone. Further testing is currently being conducted on normalization in the duration dimension. [Work supported by Sigma Xi.]
The effect of stimulus familiarity on magnitude-estimation scaling of different languages
Authors: Fucci Donald , Bettagere Ramesh , Gonzales Maria D. , Reynolds Mary E. , Petrosino Linda
Published: October 2005

The purpose of this study was to examine listener’s abilities to judge the subjective parameter of loudness of familiar and unfamiliar spoken languages. Two groups of subjects consisting of 20 adults each, ranging in age from 20–32 years, participated. Group 1 consisted of subjects who were familiar with English and not familiar with Hindi. Group 2 consisted of subjects who were familiar with English as well as Hindi. Two separate magnitude-estimation scaling tasks were performed. For the first task, subjects in both groups were instructed to assign a numerical value that corresponded to the loudness of each of nine suprathreshold intensity levels of an English sentence. For the second task, subjects in both groups were instructed to assign a numerical value that corresponded to the loudness of each of nine suprathreshold intensity levels of the same sentence spoken in Hindi. Statistical analysis showed no significant difference between the two groups in the scaling of the English and Hindi sentences. Results suggested that magnitude-estimation scaling appears to be an effective measure of loudness of familiar and unfamiliar languages, and that subjects scale the loudness of a familiar language the same way as they scale the loudness of an unfamiliar language.
Talker-based selective adaptation
Authors: Starr Gary E. , Pitt Mark A.
Published: October 2005

When during perception does the auditory system differentially process certain classes of sound objects? For example, in some models of speech perception, only phonetic stimuli are processed in the highest levels of analysis. Prior work in this lab [M. A. Pitt, 2975(A) (1994)] found that stimuli varying in musical timbre yielded selective adaptation results qualitatively similar to those obtained with phonetic stimuli. The generality of this finding was assessed by conducting comparable experiments on a nonphonetic dimension that originates from the same source as a phonetic percept: talker identity. Two selective adaptation experiments were conducted using a voice continuum. Talkers spoke the same vowel. Endpoint adaptors and different-vowel adaptors were presented ipsilateral and contralateral to the ear of identification. Results are similar to prior findings, and suggest that these classes of objects are processed similarly to a fairly abstract level of analysis. [Research supported by NIH.]
Differential masking of individual words within a sentence
Authors: Bell Theodore S. , Wright Richard
Published: October 2005

Three experiments tested the effectiveness of adjusting the amplitude of a noise masker to selectively alter intelligibility of individual words within sentences. Stimulus sentences contained three key words; all were commonly used and phonetically unique. A speech-shaped noise was presented at 65 dB SPL for all experiments. The initial study tested 12 listeners under two conditions: the noise level remained flat, or was attenuated 6 dB under the middle key word. The speech was presented at 54 and 58 dB SPL. The middle key word improved by as much as 30% (p<0.001), while other key words were unaffected. In the next two experiments, the noise was either increased or decreased by 3 dB at a key word. In one, the manipulation was at the first key word, and in the other was at the last key word. In both experiments, the speech was presented to ten listeners at 56 dB SPL. The 3-dB increment in noise significantly decreased the word’s intelligibility, and the 3-dB decrease increased the intelligibility (p<0.01) without affecting other key words in the sentence. This technique has application in reducing variability in sentence intelligibility and greatly reducing perceptual dynamic range. Implications for ‘‘all-or-none’’ contextual recognition in adverse conditions are discussed.