bluuebunny/crossref_metadata_2025 huggingface dataset:
Apparatus to determine the complex mass density of a viscous fluid contained in a rigid porous solid from acoustic pressure measurements
Authors: Mirick Robert A. , Baker Steven R. , Wilson Oscar B.
Published: October 2005

Two experimental techniques to determine the frequency-dependent complex mass density of a viscous fluid contained in a rigid porous solid are being investigated. The fluid-filled solid is contained within a small (≪λ) cylindrical cavity. In one technique the moving mass of the fluid is sensed by the effect it has on the measured input electrical impedance of a moving coil transducer. In the second technique the moving mass is extracted from the measured pressure required for the fluid to oscillate with a known amplitude through the porous solid. Preliminary results have been reported for the impedance method [Grant et al., J. Acoust. Soc. Am. Suppl. 1 84, S176 (1988)]. Preliminary results for the pressure technique and a comparison of the two methods will be presented. [Work sponsored by NRL-USRD and the Naval Postgraduate School.]
The effect of onset asynchronies between components on the ability to detect a delayed component embedded in a diotic complex
Authors: Stellmack M. A. , Dye R. H.
Published: October 2005

The purpose of this study was to extend the author's previous research on the processes that produce interference when observers attempt to lateralize a target component in the presence of other components. The present study examines the effect of an onset asynchrony between an interaurally delayed target (IDT) and dietic “distractor” components. Threshold ΔIDTs were measured for a 753-Hz tone presented against a diotic background of six additional components with Δf's of 10, 50, or 100 Hz. Onset asynchronies between the distractors and target were 0, 50, 100, or 200 ms, with the distractors always gated on first. The duration of the target was always 200 ms. The duration of the distractors was such that they remained on for the duration of the target (all components were gated off simultaneously). The rise/decay time of all components was 10 ms and each component was presented at 55 dB SPL. The largest thresholds were obtained when Δf was 50 Hz at each onset asynchrony. One subject showed no effect of onset asynchrony and the second subject showed no effect for Δf = 100 Hz, with thresholds increasing with increasing onset asynchrony when Δf was 10 or 50 Hz. These results show that onset asynchrony between components does not diminish the effects of spectrally synthetic binaural processing. [Work supported by NIH.]
Onset coding of spatial information in trains of identical transients
Authors: Saberi Kourosh , Perrott David R.
Published: October 2005

In a study of the effects of onsets in lateralizing bursts of noise, Tobias and Schubert [J. Acoust. Soc. Am. 31, 1595–1605 (1959)] demonstrated that, depending on the duration of the ongoing noise burst, it takes anywhere between 4 to 35 times as much onset interaural time disparity to offset ongoing disparities. They, therefore, demonstrated that onsets do not necessarily provide the major cue to auditory localization. In the present study, onset and ongoing information in a lateralization paradigm is set in spatial conflict to determine the amount of onset interaural difference of time (IDT) necessary to offset ongoing IDTs of transient trains of various durations. The major difference between this study and the Tobias and Schubert study was that this study used identical transients [e.g., interclick interval (ICI) = 1.5 to 2 ms corresponding to a 500- to 750-Hz tone] and not noise bursts. Unlike the Tobias and Schubert study, it was found in this study that a single dichotic click could easily lateralize a contralateral transient train of up to 200 clicks; producing the sensation of a tone lateralized to the position of the initial event. Various ICIs and ongoing durations were tested. In such a context, the precedence effect, the Franssen illusion, and the formation of auditory objects will be discussed. [Work supported by NSE and NIH.]
An investigation of the relationship between upward refraction above a complex impedance plane and the spherical wave evaluation for a homogeneous atmosphere
Authors: Rasper Richard , Baird Gordon E. , Wu Wenliang
Published: October 2005

A residue series solution based on Fock's work in electromagnetic propagation has been used by several investigators to examine sound propagation into a shadow zone. In this paper it is demonstrated that this solution merges smoothly into the Sommerfeld solution for sound propagation above a flat surface as the sound velocity gradient goes to zero. A principle thrust of this investigation is the behavior of the sound propagation above a complex impedance plane as the gradient becomes finite. Initial work indicates that the surface wave pole may contribute to the residue series solution under certain conditions.
Discrimination of partially correlated temporal sequences
Authors: Sorkin R. D. , Pezzo M. V. , Elvers G. C.
Published: October 2005

How do observers determine whether two equitone sequences have the same or different temporal patterns? On each trial of this experiment, observers were presented with two sequences of n tones (n = 8, 12, or 16; tone duration = 35 ms; frequency = 1000 Hz; level = 71 dB). The sequences were played successively and the observers had to report whether the temporal pattern of intertone gaps was the same or different in the two sequences. On half of the trials, the sequences of gaps were identical (perfectly correlated, ρ = 1), and on half of the trials the sequences were partially correlated (0 < ρ < 1). The gaps were determined by summing two random processes, one common to each sequence and one unique; this procedure allowed control of the correlation, mean, and standard deviation of the gap sequences. Observer performance (d′) increased with the magnitude of the gap variance and decreased with the correlation between the sequences. A model based on computation of the sample correlation, limited by an internal temporal variability of approximately 15 ms, predicted observer performance in a variety of conditions. [Work supported by AFOSR.]
Some acoustical properties of diphthongs
Authors: Gottfried Michael
Published: October 2005

One approach to describing diphthongs is to consider them as consisting of a steady-state nucleus and a glide toward another steady-state segment. This study evaluates this approach when sources of acoustic variation (change of speaker, stress, and rate) are introduced. In a preliminary study, four speakers of Midwestern American English were recorded producing diphthongs in isolation and in the context /K_T/. On the basis of the first three formants, diphthongs can indeed be characterized in terms of two kinds of spectrally defined states, steady-state and glide. There is, however, variation in the number and order of these states for particular diphthongs. Plots of these spectral patterns in an auditory-perceptual space [J. D. Miller, J. Acoust. Soc. Am. 85, 2114–2134 (1989)] suggested that diphthongs can be differentiated by a combination of distinctive nucleus zones and angular movements within the space. Productions by two speakers of a carrier sentence containing diphthongs under varied stress and rate conditions are being analyzed. Results will be used to evaluate the usefulness of the descriptive scheme noted above and the ability of the auditory-perceptual space to capture differences between diphthongs. Results of this evaluation, in addition to durational measurements of individual diphthongs and their component segments, will be reported. [Work supported by NINCDS.]
Masking in simulated free-field
Authors: Divenyi Pierre L.
Published: October 2005

R. W. Gatehouse [Proc. 12th I.C.A. 2, B2-7 (1986); J. Acoust. Soc. Am. Suppl. 1 82, S108 (1987)] reported a free-field masking effect that appears anomalous on the surface: A pure-tone probe positioned at a nonzero azimuth is maximally masked by a broadband noise when the azimuthal position of the masker does not coincide with that of the probe. In the present experiments, similar results were obtained with stimuli presented in a simulated free-field using head-related transfer functions measured in an artificial head [J. Blauert and P. Laws, Acustica 29, 273–277 (1973)], with a 3-kHz probe located at a 45° left azimuth and a white-noise masker positioned at either 45°, 30°, or 20° left azimuths. Maximum masking was observed at the 30° noise location. This nonmonotonic masking effect may not be due to anything but the head-induced diffraction patterns characteristic to the 3-kHz range: Measurement of the noise power (at the output of the transfer functions inside the 1/3-oct band surrounding the probe showed that, as the noise was displaced from the 45° left to the 30° left position, the decrease of the noise level in the left ear was less important than the increase in the right ear. Adding this variable-level noise to the fixed signal should thus result in monaural masked thresholds that are not appreciably different in the left (i.e., the near) ear but that monotonically increase with decreasing left azimuths in the right (i.e., the distant) ear. These predictions were, indeed, confirmed by results of masking experiments using the same stimuli presented monaurally on the two ears. [Work supported by Department of Veterans Affairs.]
Airborne sound transmission across resilient mounts
Authors: Shaw Michael F. , Burroughs Courthey B.
Published: October 2005

The airborne transmission loss across resilient mounting systems is investigated by developing an analytic model of the transmission of vibration from a point-driven, simply supported plate to a parallel infinite plate through the air separating the plates. Predictions of airborne transmission losses are compared with transmission losses through resilient mounts to quantify the role of the airborne path in transmission losses through well-designed, single-stage resilient mounting systems. The sensitivity of the airborne transmission losses to separation distance, thickness of the receiving plate, size of the driven plate, and damping in the plates are presented.
Noncompressible liquid layer elasticity phenomenon
Authors: Babeshko Vladimir A.
Published: October 2005

A vibration process localization phenomenon, arising in semi-infinite regions, is known to exist in media other than solid deformable media. An infinite layer of an ideal incompressible liquid r + h deep is in contact with an elastic plate, vibrating at the frequency ω. Analysis of this system shows that for some vibrating plate size and mass, energy propagates to infinity unattenuated. The conditions favoring such vibration processes when unrestricted resonances can arise are presented [V. A. Babeshko, Lett. J. Technol. Phys. 14 (8) (1988)].
Finding and using stress accent in spoken language understanding
Authors: Steele Shirley A. , Liebowitz Suzanne A.
Published: October 2005

Stress accent is a feature of the prosodic system in English that functions syntagmatically to organize an utterance into shorter sections. Knowledge about the location of stress accents in the segmental stream can help a speaker-independent spoken language understanding system prune the search space, e.g., for the correct lexical item or the correct pragmatic interpretation. Unlike automatic systems, human listeners are able to locate accents because they know what accented versus unaccented syllables sound like and because they can normalize for such things as speaker and speaking rate. Here, the results of a study designed to locate accents in continuous speech are reported. An attempt is made to use both speech knowledge and normalization by identifying salient characteristics of accent in training data along with accent characteristics of the test utterance. Accented and unaccented syllables are separated using selected clustering algorithms on a feature space of energy and duration measures. In addition, some specific ways in which the output of the accent finder can be used by other components of the system (e.g., lexical access, pragmatics) are suggested. [Work partially supported by DARPA/ISTO.]
Bandwidth and absorption effects on intensification in a structural-acoustic enclosure
Authors: Peretti Linda F. , Dowell Earl H.
Published: October 2005

Asymptotic modal analysis (AMA) provides a formal method to analyze high modal density sound fields in enclosures. Typically, uniform response levels occur throughout the interior. Exceptions occur at physical boundaries of the enclosure, and at theoretical boundaries that are created due to the symmetry of certain loading conditions. The transition from elevated response at a boundary to uniform interior response is studied as a function of the ratio of bandwidth to center frequency)fh/fc), for combinations of 1-, 2-, and 3-D modes emanating from corners, edges, and walls (in the case of a rectangular enclosure). The size of the transition region seales with the center frequency and is affected by the bandwidth to center frequency ratio in varying degrees depending upon mode type and geometry. In the AMA limit, the intensification zone can be described by a local solution that is independent of the enclosure dimensions. Wall absorption affects the character of the intensification zone, and this effect is studied for various fh/fc ratios. Local solutions formed from the superposition of oblique waves provide the formulation for intensification behavior. By expanding the result in a Taylor series about the center frequency, the intensification zone can be described by a set of universal curves that contain the center frequency effect and a bandwidth correction. [Work supported by NASA Langley Research Center.]
Physiology of creaky voice and vocal fry
Authors: Scherer Ronald C.
Published: October 2005

Creaky voice and vocal fry are voice qualities that are linguistically normal but often symptomatic in voice pathology. The physiology of creak and vocal fry will be discussed from the standpoints of electromyography, videofiberoscopy, x-ray, glottography, and aerodynamics. Discussion will emphasize the relative role of the cricothyroid and thyroartenoid muscles, laryngeal vestibule constriction, hyperadduction, vocal fold motion irregularity, subglottal pressures, mean flow, and glottal source flow. New data in these areas will be compared with earlier findings. [Work supported by the Bonfils Foundation.]
Cross-linguistic relations between voice quality and vowel quality
Authors: Denning Keith
Published: October 2005

A survey of impressionistic and instrumental descriptions of diverse languages (including new data from the Nilotic languages Dinka and Acholi) reveals repeated cases of phonemic and subphonemic interaction between phonation type and aspects of oropharyngeal resonance. Generally, if there is a regular interaction between intra- and extralaryngeal factors in a language, vocal fold configurations with greater laryngeal laxness (as required for regular phonation in consonants, murmur in consonants and vowels, and pitch depression) are associated with lower F1 and, conversely, greater vocal fold tension (associated with voicelessness, creaky phonation, and higher pitch) occurs with higher F1. Explanations for this universal in biomechanical (Laver, 1980), neuromuscular (Laufer and Condax, 1981), and aerodynamic (Ohala, 1983) aspects of articulation are proposed. Cross-linguistic evidence suggests that articulation from intra- and extralaryngeal domains (putatively separate for phonological purposes) may function distinctively only in combination with each other in many cases. Implications of these and other findings include the need for a distinctive feature of “complex voice quality,” in contradistinction to the “primary feature” approach of Stevens, Keyser, and Kawasaki (1986), and the desirability of phonological models that accommodate phonetically based patterns of the relevant type in formulating principles of sound change and synchronic phonological analysis.
Nonlinear aspects of ultrasonic heating
Authors: Carstensen E. L. , Dalecki D. , Parker K. J. , Bacon R. , Blackstock D.
Published: October 2005

Under appropriate conditions, the absorption of finite amplitude ultrasound is determined largely by source amplitude, field geometry, and the nonlinear properties of the medium and is only weakly dependent upon the small signal absorption coefficient of the material. The characteristics of this absorption are completely foreign to the ideas that we have come to associate with small signal losses. Under certain conditions, finite amplitude absorption is somewhat greater in focused than in plane-wave fields. Under medically relevant conditions, heating of tissues may be enhanced by a factor of 3 or more by nonlinear phenomena. Some commercially available diagnostic instruments may be capable of producing focal pressure amplitudes high enough to result in nonlinear contributions to local heating. The resulting total temperature increments could exceed the 1°C, the value universally regarded as safe. Finite amplitude processes affect the thresholds for tissue damage. The characteristics of the threshold curves differ qualitatively depending upon whether they are expressed in terms of local or source intensities. [This work was supported in part by U.S.P.H.S. Grant No. CA39241.]
Biophysical characterization of diagnostic ultrasound equipment
Authors: ter Haar Gall , Duck Francis
Published: October 2005

Concern for the safety of diagnostic ultrasound procedures has meant that there has been a move to classify ultrasonic scanning equipment in terms of the physical effects it can produce in biological tissues. To this end, different types of diagnostic equipment currently in use in the clinic have been characterized in terms of their heating effects, thor ability to induce cavitation bubbles in agar gels, the streaming velocity attained under free-field conditions in water, and their ability to produce sonoluminescence. The occurrence and extent of these phenomena have then been studied in the light of the acoustic parameters (such as peak positive pressure, peak negative pressure, spatial peak temporal average intensity, etc.) used to produce them. Extensive characterization of the machines investigated was carried out using a beam calibrator. It was found that none of the acoustic parameters measured provided an unambiguous indication of the extent to which any of these physical mechanisms would occur, thus rendering it difficult to predict safety on this basis from a listing of acoustic output.
Voyager flight crew hearing threshold levels resulting from 5- and 9-day continuous in-flight noise exposure
Authors: Stephenson Mark R. , Billings Bradley L. , Jutila George A.
Published: October 2005

The flight crew of the Voyager aircraft was continuously exposed to a broadband noise for nearly 5 days during a trial flight, and for over 9 days during their nonstop flight around the world. Evaluation of the threshold shifts resulting from these exposures represents a unique opportunity to study the effect of human exposure to intense continuous noise for such durations. Post-flight audiometry demonstrated that the 9-day flight did not result in larger hearing threshold shifts than those following the 5-day flight. Neither crewmember incurred a permanent threshold shift from these exposures.
Equalization using voice and music as the source
Authors: Meyer John
Published: October 2005

A source-independent technique to measure accurately the amplitude and phase response of sound systems in concert halls is discussed. Measurements may be made during live performances or events, using music or voice as the test signals. Correlation is shown between the impulse response and the results obtained using music signals. An equalizer that corrects for many room resonances in both amplitude and phase simultaneously has been developed. The effect of this equalizer on concert systems in an existing venue is shown.
Hearing conservation programs (HCPs): The effectiveness of one company's HCP in a 12-h workshift environment
Authors: Reynolds Jacqueline L. , Royster Larry H. , Pearson Richard G.
Published: October 2005

A hearing conservation program (HCP), originally designed for an 8-h workshift schedule, was evaluated at a plant site where a 12-h workshift schedule is now utilized. The study included three phases: a noise analysis of the work environment, HCP evaluation using audiometric database analysis (ADBA), and an evaluation of the hearing protection devices (HPDs) used at the facility by measuring temporary threshold shift (TTS) and applying ADBA procedures. The overall measured employee TWA in the process area where the TTS study was conducted was 92 dBA. The ADBA results indicated that the existing HCP is, at best, marginal. The most likely causes of this less than desirable rating are inadequate audiometric testing procedures and inadequate HPD utilization. It was concluded that the introduction of the 12-h workshift has had no impact on the present effectiveness of the HCP. All three HPDs in use at the facility (3-M foam earplug, E-A-R foam earplug, and Bilsom Soft earplug) offered effective protection from noise at all audiometric test frequencies (0.5 to 6 kHz) except 0.5 kHz. All three HPD wearer groups exhibited mean TTS at 0.5 kHz, which was significantly different from zero at the 0.05 level for the E-A-R and 3-M wearer groups.
An improved modeling technique for high-order acoustic spectra
Authors: Raman Vijay , Mohammed Osama , Yen Kang , Ramdin Kurt
Published: October 2005

The analysis and modeling of noisy environments are considered in this work. Parametric modeling is often the most convenient, since it can be used as a basis for parametric filtering and adaptive filtering for noise reduction. The earlier work of these researchers dealt with the development of autoregressive (AR) as well as the autoregressive-moving-average (ARMA) modeling of a data set taken from digitized recordings of a typical industrial environment. It was shown therein that the order of the model required is extremely high due to the periodic components, and is therefore not as useful as expected. In this work, a new approach is developed to model periodic components and the random part sequentially, not separately. This method is able to model the data set with much fewer coefficients than in the standard parametric models, and is useful in designing the noise-reduction filter. [Work supported by the Florida High Technology and Industry Council.]
Comparison of levels for ultrasonic cavitation in neonatal mice and other mammals
Authors: Frizzell Leon A.
Published: October 2005

The level for cavitation involvement in hind limb paralysis of the mouse neonate has been determined at 10°C and 37°C at 1 MHz. These levels are compared to levels for cavitation as reported in other mammalian systems. Results have also been obtained for pulsed exposures, and a comparison is made between results from continuous wave and pulsed exposures. It is suggested that the pulse average intensity and total sound on time may be more useful parameters (as opposed to time average intensity and exposure duration) for comparing pulsed and continuous wave cavitation results within certain exposure regimes. This may prove to be a useful approach to the incorporation of continuous wave results, relating to cavitation, in the determination of safe levels of exposure to diagnostic ultrasound.
Intensity gain criteria for focused ultrasound tumor hyperthermia: Theory and in vitro experiments
Authors: Davis Brian J. , Lele Padmakar P.
Published: October 2005

Plano-concave lenses and concave radiators used in scanning focused ultrasound systems have well-established capabilities for deep and selective tumor hyperthermia. The focal intensity gain, a good predictor of selective heating, is expressed as a function of the treatment depth below a planar beam portal integument, frequency-dependent tissue absorption rate, wavenumber, and aperture angle. From this expression novel and useful relations are derived for the maximum focal gain as a function of system specific maximum aperture angle, optimum frequency, and other parameters. Temperature distributions from in vitro and tissue phantom experiments designed to establish minimum gain criteria for selective heating with “pivoted” and circular scanned focused beams are presented. Measured intensity fields are compared with numerical models that aim to (1) solve the diffraction pattern of an absorbing spherical lens coupled to a clamped piston radiator, (2) predict the intensity field of a focused beam in an absorbing medium, and (3) account for lens propagation that is not parallel to the beam axis. [Work supported by USPHS Grant No. 31303 and the Lutheran Brotherhood.]
Synthetic speech audiometry
Authors: Bickley Corine , Kidd Gerald
Published: October 2005

A new hearing test is being developed that is based on presenting to listeners sets of synthesized words with well-defined acoustics properties. The test is based in part on work by Gòsy et al. [Proc. 11th ICPS, Tallinn (1987)], and its aim is to estimate a listener's hearing sensitivity from errors in word discrimination. Sets of words have been synthesized (using the Klatt synthesizer) that differ from each other by one of two phonemes (e.g., sit sat fat fit). The synthesis was guided by two goals. (1) Each word should differ from another word in a set by only one acoustic feature; the primary difference must be limited to a specific frequency band (e.g., sit versus sat differ by the frequency of the first formant). (2) The synthesized words should be highly intelligible to normally hearing listeners in a quiet environment. Initial results were obtained by presenting the synthesized words combined with white noise of various levels in a forced-choice paradigm to normally hearing subjects,. As expected, word discriminability was correlated with the salience of the acoustic feature that distinguishes the word relative to the added noise. The feasibility of using synthesized word sets of this type to detect and estimate the severity of hearing impairment will be discussed. [Work supported by a grant from NIH.]
The influence of selected acoustic cues on the perception of /l/ and /w/
Authors: Espy-Wilson Carol Y.
Published: October 2005

In a semivowel recognition system developed by Espy-Wilson [Mass. Inst. Technol. Res. Lab. Electron. Tech. Rep. No. 531 (1987)], the sounds /l/ and /w/ were frequently confused, especially when they occurred intervocalically. In this study, the perceptual importance of some of the cues used in the recognition system, as well as some others which appear to be salient, were investigated. An [ala]-[awa] continuum was synthesized. The starting point was an easily identifiable [ala] stimulus. Three factors were varied orthogonally to shift the percept towards [awa]: (1) the rate of change in the formant transitions between the semivowel and following vowel, (2) the rate of change in the amplitudes of F3, F4, and F5 between the semivowel and following vowel, and (3) the spectral shape of the semivowel (coronal or labial). Preliminary results of an identification test show that spectral shape and the rate of change of the formant transitions are important cues, whereas the rate of change in the amplitudes of F3, F4, and F5 appears to have a negligible effect on listeners' responses. For example, with formant transitions of 30 ms or less, [ala] is heard. With formant transitions greater than 40 ms, the perception moves towards [awa]. The results also show that a few listeners had difficulty hearing [awa] when the semivowel had a coronal shape, despite the rate of change in the formant transitions being biased towards /w/. These results will be discussed with respect to past and future research in speech recognition.
Design of polymers for viscoelastic damping applications
Authors: Wetton R. E. , Duncan J. L.
Published: October 2005

The large frequency dependence of the dynamic moduli of polymers allows the design of materials with special damping and engineering applications. The temperature dependence of these properties is, however, a drawback in many cases. The present paper reviews the changes of Youngs, shear, and bulk moduli with frequency and temperature. Their accurate measurement and predictions via time/temperature superposition methods are discussed, as are the relationships between these parameters with changing temperature. The design of elastomers with high damping and minimized temperature variation is discussed with some examples.
Recent developments in parabolic equation modeling
Authors: Collins Michael D.
Published: October 2005

The parabolic equation (PE) is one of the most important computational models for underwater sound propagation. Since the PE was introduced into the field of underwater acoustics by F. D. Tappert, a great deal of research has been devoted to extending its capabilities, accuracy, and efficiency. In its present state, the PE is capable of handling three-dimensional problems, rough interfaces, and interaction with elastic ocean bottoms. A higher-order PE is accurate for arbitrarily large propagation angles. The rotated PE, which marches the solution parallel to the ocean bottom, provides improved accuracy for problems involving sloping bottoms. The efficiency of the finite-difference solution of the PE has been improved for range-dependent problems with a new algorithm for solving tridiagonal systems. The time-domain PE efficiently solves pulse propagation problems directly in the time domain. Some recent progress as well as some unresolved issues in PE modeling will be discussed.
Optimal absorber potentials in PE modeling
Authors: Ryan F. J. , Rees C. David
Published: October 2005

The parabolic equation (PE) approximation—essential in solving range-dependent propagation problem—relies on iterated fast Fourier transforms (FFTs). Preventing significant errors due to the periodicity of the finite FFT (“ringing”) requires inserting an absorber potential to confine the wave energy to the range of interest. Such potentials, or sponges, have, to date, been strictly ad hoc. The problem of creating an optimal sponge by using an optical model analogy of the reflectionless potential U = U0* [sech(a*x)]2 of 1-D quantum mechanics is studied. This approach permits the development of closed-form expressions for both transmission and reflection coefficients in terms of elementary transcendental and gamma functions of complex argument. Using these coefficients and an efficient technique for evaluating such gamma functions yields a quantitative study of the problem of the optimal sponge. These results demonstrate that, for relevant parameter domains, there may be several “branches” of minimal paths in sponge parameter space, including one particularly well suited to the demands of PE modeling. [Work supported by NOSC-IR and OCNR.]
Employing the complete acoustical palette in teleconferencing design
Authors: D'Antonio Peter
Published: October 2005

The prevailing architectural acoustics approach in teleconferencing is “Deader is better” or “No acoustics is better than bad acoustics.” In some situations, this is appropriate, but there are alternative approaches to reflection control in teleconferencing facilities which make use of the entire acoustical palette, namely absorption, reflection, and diffusion. Since the application of diffusive surfaces is new to the teleconferencing environment, a review of the development and the spatial, temporal, and spectral properties will be presented. A teleconferencing design for a board room will be proposed that makes use of an integrated suspended ceiling cloud, containing the various elements of the acoustical palette, as well as lighting, and HVAC elements. This design provides diffuse sound across the conference table, which allows a comfortable conversation level, better acoustic coverage and communication among the participants, as well as a more natural transmitted sound to the other end of the converstation. The ceiling cloud also affords a convenient approach for concealing the necessary HVAC ducts, wiring, etc. and also provides accessibility for maintenance.
The perception of timbre of steady-state complex tones
Authors: Plomp Reinier
Published: October 2005

The paper will present a review of work by the author in timbre perception. Steady-state complex tones are characterized by three perceptual attributes: loudness, pitch, and timbre. Loudness and pitch are mainly determined by a single physical parameter: loudness by intensity and pitch by the fundamental frequency. Timbre, on the contrary, is not a one-dimensional attribute: It is primarily determined by the shape of the sound spectrum and, therefore, multidimensional. This aspect of tone sensation was investigated by means of multidimensional scaling. For tones derived from musical instruments, excellent agreement between three-dimensional timbre representations and three-dimensional spectrum representations was found. The most important dimension is the slope of the spectrum: tones with strong low harmonics sound dull, tones with strong high harmonics sound sharp. Local peaks in the spectrum result in specific timbres as in speech vowels. It was found that the phase relation among the harmonics has only a minor effect on timbre. The importance of the latter finding in relation to the effect of reverberation on timbre will also be discussed.
Acoustic calibration requirements in an aerospace industry environment
Authors: Rangan L. Kasturi , Jaeger Klaus
Published: October 2005

Several types of acoustic measuring instruments are used at Lockheed Missiles and Space Company's various test facilities. Lockheed's Primary Standards Laboratory is required to calibrate these instruments. In this paper, the environments where the instruments are used, calibration requirements, traceability requirements and how they are met, calibration recall intervals, and uncertainties in the calibration standards hierarchy will be presented.
Structural damping measurements of polymer composites with laser Doppler vibrometry
Authors: Pechersky Martin J. , Gerusky Michael T.
Published: October 2005

Damping loss factors of three commercially available composites up to a frequency of 12 kHz have been performed. A resonance dwell technique was used in which both the excitation and measurement were non-contact. The excitation was accomplished electromagnetically and the driving point admittance was measured with a laser vibrometer. The 25-era-long slender beam specimens were seismically supported at two nodes for each resonance by a combination of soft springs and silk thread. The mode shapes to determine the nodes of each beam were measured prior to the damping measurements. Metallic specimens were also measured to determine the limit on the accuracy of the measurement. The damping factors for the composites (Q−1) were found to be about two orders of magnitude larger than the metallic beam and all of the composite damping factors were found to increase monatomically with the excitation frequency over the range tested. Loss factors of the composites ranged from 1 to 4 × 10−3 at the lower frequencies to about 3 to 16 × 10−3 at the higher frequencies.
Obtaining internal and coupling loss factors by a transient test method
Authors: Sato K. , Lalor N.
Published: October 2005

Statistical energy analysis (SEA) is taking an increasing role in determining energy flow and predicting noise reduction of machine structures. In order to set up the SEA model it is necessary to obtain the internal and coupling loss factors of each substructure either from theory or from measurement. The conventional measurement technique, in which steady-state input power is supplied by a shaker to each subsystem in turn, is very time consuming. Moreover, it is not always possible to attach the shaker in the best position due to space limitations. This paper describes a transient method of loss factor measurement, using an instrumented hammer, which overcomes the above-mentioned difficulties. The technique uses the point and transfer inertance data for the structure to calculate input powers and subsystem energies. Results obtained by this method are compared with those obtained conventionally and good agreeement is demonstrated.
Animal psychoacoustics
Authors: Fay Richard R.
Published: October 2005

The sense of hearing in animals has been studied quantitatively using a variety of behavioral techniques for the past 50 years. The database now existing [R. Fay, Hearing in Vertebrates: A Psychophysics Databook (Hill-Fay Associates, Winnetka, IL, 1988)] includes data for 180 vertebrate species and allows several generalizations to be made regarding the relations between human and animal hearing, the methodologies useful in animal hearing studies, and the hearing processes common to all vertebrates. Although the frequency range of hearing varies by many octaves among vertebrates, absolute sensitivity at best frequency is quite similar (± 10 dB re: 0.0002 dyn cm−2). The sound discrimination performance often, but not always, exceeds the performance of animal listeners. There are no clear phylogenetic trends toward more acute discrimination abilities in primates, and very few examples of specializations for enhanced sound discrimination abilities among vertebrates (echolocators may be exceptions). There is no single conditioning or psychophysical method that clearly gives lower or more valid thresholds. Data from the literature will be presented to illustrate these and other general conclusions about animal hearing.
Experimental verification of a spectrogram correlation theory for FM echolocation
Authors: Simmons James A.
Published: October 2005

The FM bat, Eptesicus fuscus, perceives each reflecting glint in a target as the cross-correlation function of its echoes, using a mixture of time- and frequency-domain auditory representations according to the time separation of echo components relative to the receiver's integration time of 350 μs. The accuracy of jittered-delay discrimination is as good as 10 ns. Separate jitter discrimination curves for 0° and 180° phase shifts of echoes fit together in the manner of compound period histograms to form the complete cross-correlation function of echoes. Jitter discrimination curves shift along the delay axis by − 17 μ/dB when echo amplitude changes (amplitude-latency trading), showing that the bat uses timing of neural discharges rather than extraneous, spectrally encoded cues to discriminate jittered echoes. Other recent jitter experiments missed part of these results due to an unintended masking effect. A spectrogram-with-phase representation of echoes followed by a transformation of the frequency-domain component of the spectrogram into the time domain would account for the bat's perception of the cross-correlation function. This transformation is the basis for fusing target range and target shape into unified images. These results additionally implicate vertical and horizontal localization as part of a single imaging process.
Sonar signal design of the Chinese bat Pipistrellus abramus temmink and the French bat Myotis mystacinus during natural hunting prey
Authors: Lin Zhenbiao , Lu Jin , Escudie Bernard
Published: October 2005

There are more than 100 species of bats in China. This paper gives the first description of Chinese FM bat signals and a comparison with the French FM bat. Twenty signals emitted by a South China bat, Pipistrellus abramus temmink (P.a.t.), and 49 signals by a French bat, Myotis mystacinus (M.m.), during searching, identification, pursuit, and prey capture in the field were studied via time, frequency analysis, and 3-D wideband ambiguity diagrams. The evolution of main signal parameters (duration, dominant frequency, bandwidth, and average sampling pace along the hunting track) was described as a function of estimated bat-prey distance in order to find the relation between the parameters and distance. The results suggest that the P.a.t. bat and the M.m. bat use a similar strategy of signal design although they are living in different continents, and hunting different insects in different environments. For two species of FM bats, a turning point in the parameter evolution exists at about 1.5 m between bat and prey. In our recorded signals, the M.m. bat emits much larger bandwidth and stronger harmonics than the P.a.t. bat. As a consequence, the range resolution and bearing resolution are higher for the M.m. bat than for the P.a.t. bat in this experiment. [Work supported by NSFC 1881155 of China and RCP 445 CNRS of France; partially supported by NIH grant NS 20527 to Professor P. Jen of the University of Missouri—Columbia, Columbia, MO.]
Measurement of the law strain complex extensional modulus of rabbit skin
Authors: Pereira J. Michael , Mansour Joseph M. , Davis Bryan R.
Published: October 2005

The complex extensional modulus of rabbit skin was measured by recording acoustic pulses propagating along thin strips of skin excised from the backs of rabbits. In the experiment, a step change in displacement was introduced into the skin sample by a speaker, to which one end of the sample was attached. The response was recorded at different locations along the sample by a phonograph pickup. The nominal static stress on the samples during the experiments was maintained at a low level (1500 Pa). Repeatable results for the attenuation, speed, and viscoelastic storage and loss moduli were measured in the frequency range of 200–1000 Hz. In this frequency range, the attenuation was approximately linearly proportional to the frequency and the speed was approximately constant. The storage and loss moduli were also approximately constant in this frequency range, with mean values of 179 300 Pa and 113 700 Pa, respectively. [Work supported by NIH.]
Improved spatial resolution of fish using hydroacoustics
Authors: Patrick P. H. , Sim B. , Hunt G.
Published: October 2005

Investigations were conducted in the laboratory on the accuracy of a commercial sonar system in detecting underwater targets. Accurate spatial resolution of fish is necessary for reliable estimates of biomass and for classifying fish species. Results suggested that the sounder was limited in target separation below 25 cm at a transmitted pulse of 0.1 ms. Modifications to equipment resulted in an improved resolution (to approximately 10 cm) of targets in both vertical and horizontal tank experiments. Target strength estimates were also determined. The application of hydroacoustics to detect and classify fish is discussed. [Work supported by Ontario Hydro.]
The threshold recovery pattern between 48 h to 30 days after exposure to 50-μs arc-discharge impulse noise in guinea pigs
Authors: Gao Wenyuan , Yuan Fanming
Published: October 2005

The threshold recovery pattern 48 h after exposure to arc-discharge impulse noise was investigated. Guinea pigs, implanted with chronic electrodes, were measured in quiet using a click average-evoked response technique. The animals were exposed to ten impulses (1/min) of either 170-(N=10), 166-(N=17), 163-(N=15), 160-(N=9), or 157-(N= 16) dB peak SPL. The A duration was 50 μs, and the rise time was 10 μs. Recovery threshold was monitored, at 48 h, at 8, 15, 22, and 30 days, respectively, after exposure. Some of the animals were then sacrificed for cochlea histology. The results were as follows. (1) The recovery patterns varied with peak amplitude of impulse noise, i.e., they were linear in log time of 157 and 160 dB; they were nonmonotonic in log time of 163 and 166 dB, and there was no recovery but a growth pattern at 170 dB. (2) The period between 8 to 15 days post exposure is an important period for turning to permanent threshold shift (PTS); i.e., if the recovery goes on in this period, it will show no PTS. (3) This kind of impulse noise with short duration and rapid rise time may be more harmful to the audition than the other kind.
Ballistic phonon mediated detection of elementary particles in silicon
Authors: Neuhauser B. , Cabrera B. , Lee A. T. , Young B. A. , Martoff C. J. , McVittie J. P.
Published: October 2005

When an incident particle collides with an electron or nucleus in a silicon crystal, 70% of the recoil energy is converted into a burst of low-energy phonons. These phonons propagate ballistically for distances of several centimeters if the crystal has very few defects or impurities and if it is cooled to a temperature well below 1 K. Direct sensing of the phonons is the basis for a new type of elementary particle detector, called a silicon crystal acoustic detector (SiCAD), which will be used in neutrino experiments and in the search for other weakly interacting particles. The first generation of ultrasensitive phonon detectors consists of a thin film strip of a superconducting material, which is current biased just below the critical temperature. Incident phonons drive a segment of the film normal and thereby produce a voltage pulse. These devices have sufficient sensitivity and resolution to detect energy depositions of several keV in standard 3-in. silicon wafers. Research currently is in progress on the next generation of phonon detectors that will make use of superconducting tunnel junctions. [Work supported by DOE, NSF, and Research Corporation.]
Using a SQUID acoustomagnetic spectrometer to characterize continuous wave acoustic response observations
Authors: Sundfors Ronald K. , Holland Mark R.
Published: October 2005

A SQUID acoustomagnetic spectrometer is used to detect changes of magnetization of tantalum metal produced by a continuous wave composite resonator in an external magnetic field. Acoustic power variations produce temperature variations in the spectrum and thus cause changes in the Curie susceptibility of the paramagnetic impurities present in the sample. Swept frequency acoustic spectra of single-crystal tantalum standing wave resonances at the normal mode frequencies (mechanical resonances) are studied at 4.2 K. Depending on the rate of frequency sweep through a mechanical resonance, the applied acoustic power, and the magnetic field, the observed structure at the mechanical resonance frequencies can be both above and below the baseline. The low-frequency side of each structure has a Lorentz line shape and the high-frequency side has an exponential decay that is explained by heat exchange between sample and surroundings. This interpretation allows these structures to be used in general in continuous wave velocity of sound and ultrasonic attenuation studies while making use of the high sensitivity of the SQUID acoustomagnetic spectrometer.
Automatic evaluation of English spoken by Japanese students
Authors: Bernstein Jared , Weintraub Mitch , Cohen Mike , Murveit Hy
Published: October 2005

The paper describes the methods and results of a study of the feasibility of automatically grading the performance of Japanese students when reading English aloud. SRI recorded 31 adult Japanese speakers: 22 men and 9 women. Each Japanese speaker read six sentences aloud. All 186 recorded utterances were presented in a random order for rating by three expert listeners who rated the utterances on two occasions. Speech-grading software was developed from an adaptive hidden-Markov-model (HMM) speech-recognition system. The grading procedure is a two-step process: First, the speech to be graded is aligned, then the segments of the speech signal that are located are compared with models of those segments that have been developed from a database of speech from native speakers of English. Important points in the results are: (1) ratings of speech quality by expert listeners are extremely reliable, and (2) automatic grades from the system correlate well (>0.8) with those ratings.