bluuebunny/crossref_metadata_2025 huggingface dataset:
Stress and interstress intervals in reading
Authors: Fant Gunnar , Kruckenberg Anita
Published: October 2005

Objective and subjective measurements of syllabic stress in reading of a Swedish novel have been performed. Our data bank contains material from 16 speakers. Measurements of durations and local pitch variations correlate well with the direct subjective estimate of stress. A comparison is made of subjects' introspective grading of stress from silent reading and their ability to discriminate individually produced stress patterns. The top-down influence is partial only. Statistics of interstress intervals show that relations between interval durations and the number of phonemes in an interval display speaker-specific characteristics. Moreover, the average of stress intervals not spanning across syntactic boundaries constitutes a rhythmical time constant of the order of 0.5 s in the planning of pauses, such that the sum of physical pause plus terminal lengthening tends towards an integral multiple, 1, 2, or 3, of the time constant. These data support and extend the model of W. A. Lea [Trends in Speech Recognition (Prentice-Hall, London, 1980)]. [Work supported by the Swedish Board for Technical Development and The Bank of Sweden Tercentenary Foundation.]
Pitch dynamism in bilingual females and males
Authors: Henton Caroline G.
Published: October 2005

Pitch dynamism refers to how rapid or slow are changes in pitch range from high points to low points, and vice versa. Previous studies of pitch have focused largely on average pitch. Dynamism has been little explored instrumentally, and scarcely at all with regard to the variable speaker sex. Using recordings of female and male bilingual speakers, dynamism will be measured on the basis of first-differentiated fundamental frequency curves. These data will be used to explore whether there are intersex differences in pitch dynamism, and whether there is variation according to language spoken. Findings will be related to previously reported results for pitch ranges by females and males. Taking the combined results, it will be possible to respond empirically to stereotypes existing for more excitable or more variable speech for female speech, a response that has been urged by, e.g., Kramer (1977), McConnell-Ginet (1983), and Smith (1985).
A methodology for analyzing prosody
Authors: Price P. , Ostendorf M. , Shattuck-Hufnagel S. , Veilleux N.
Published: October 2005

Prosody consists of that information in speech which can be suprasegmental, i.e., operate over units larger than a single segment. Prosodic contours may span a word, phrase, or larger units. The goal of this study is to understand the mapping between discrete, abstract units (e.g., boundary tones, pitch accents) and their observed continuously varying acoustic correlates (e.g., duration and F0). Since prosody synthesis and analysis have traditionally been a challenging problem, the initial focus of this study has been restricted to the FM radio news broadcasting style of speech. This pilot study indicates that in this speech style, prosodic units appear to be more strongly and more regularly marked than in conversational styles. Time- and pitch-scale modification is employed using a sinusoidal model to change the duration and F0 contours of natural utterances. This technique allows synthesis of an utterance with a new prosodic contour, taking the input parameters from a linguistic model of prosody, or from another utterance with different phrasing. In this way, the perceptual effectiveness of various models in marking prosodic prominences and boundaries can be explored. The details of the method will be discussed, and a sample tape will be played.
An exact solution for finite-amplitude plane sound waves in a dissipative fluid
Authors: Mitome Hideto
Published: October 2005

The propagation of finite-amplitude plane sound waves in a dissipative fluid can be described by Burger's equation, and its exact solution obtained [D. T. Blackstock, J. Acoust. Soc. Am. 36, 534–542 (1964)]. In this paper, an exact solution for sound pressure, which is suitable for the direct numerical computation of the waveform in the time domain, is derived. Numerical results show that this solution describes the whole propagation process, including shock formation and its decay. Computation is possible up to Γ = 175, where Γ is the Goldberg number indicating the importance of nonlinearity relative to dissipation, for any value of X (distance normalized by shock formation distance). Although it becomes difficult above this value (except at larger X's) because of its functional form, the solution connects smoothly with the Fubini solution at X < 1 and the Fay solution at X > 3.5. Since this solution is exact and gives the waveform at any position, it can serve as a standard solution for various approximate solutions. As an application, the saturation for the fundamental component and that for the entire wave are shown.
Planning school and college music facilities
Authors: Geerdes Harold P.
Published: October 2005

Educational music facility planning has become a specialty within the broad field of acoustics. While teaching, rehearsal, and performance spaces for school and college music departments share many of the requirements for downtown concert halls and opera houses, they are in many ways unique. A school or college music facility planner ideally combines a practicing background as a teacher and conductor with knowledge and experience in room acoustics, noise control, and electronic systems. As a member of the design team, he represents the music staff of the educational institution and articulates their needs to the other planners. Throughout the design development process he provides a level of expertise beyond that of the music educator. A close relationship with the 55 000 member Music Educators National Conference is very beneficial. The educational music facility planner can work under contract with the client or with the architect, depending on the particular circumstances, or he may work for a firm of established acoustical consultants who wish to use his special experience and expertise to supplement their own.
The acoustic design of recital halls for educational facilities
Authors: Jaffe J. Christopher
Published: October 2005

A recital hall for an educational facility requires a close appraisal of anticipated teaching, rehearsal, and performance use. In most cases, a modified set of acoustic criteria is required for these spaces in contrast to those associated with the design of professional recital halls such as Weill Hall, Town Hall, or the 92nd Street YMHA. This paper discusses the special requirements of recital halls in educational facilities, recognizes the work of Rein Pirn in this area, and develops a revised scale for volume-to-seating area ratios for these rooms. Qualitative subjective judgments related to the ratio of direct-to-reverberant energy are reviewed and measurements taken in some representative recital halls are analyzed.
Schnitger meets Sabine: Designing for organs
Authors: Mahoney Robert F.
Published: October 2005

In the planning of music education facilities there are few areas that afford the possibility of collaboration between the acoustician and the instrument builder; the design of spaces for organ practice and performance is one of these. The organ builder has within the traditions of his or her craft considerable latitude in regard to tonal design, pipe scaling, and the disposition of various divisions. The acoustician, on the other hand, must serve an organist who is likely to relish a highly diffuse and reverberant sound, but who is often confined to practice rooms of limited volume and is seated close to a powerful instrument of considerable physical extent. In addition to the customary concerns of adequate isolation and suitable background sound levels, the designer must marry the room acoustical design to the characteristics of the instrument to be installed there, recognizing the distinction between practice and performance environments.
Experimental measurement of structural power flow on an aircraft fuselage
Authors: Cuschieri J. M.
Published: October 2005

An experimental technique is used to measure the structural power flow through an aircraft fuselage with the excitation near the wing attachment location. Because of the large number of measurements required to analyze the whole of an aircraft fuselage, it is necessary that a balance is achieved between the number of measurement transducers, the mounting of these transducers, and the accuracy of the measurements. Using four transducers mounted on a bakelite platform, the structural intensity vectors at locations distributed throughout the fuselage are measured. To minimize the errors associated with using a four-transducer technique the measurement positions are selected away from bulkheads and stiffeners. Because four separate transducers are used, with each transducer having its own drive amplifier, phase errors are introduced in the measurements that can be much greater than the phase differences associated with the measurements. To mimimize these phase errors two sets of measurements are taken for each position with the orientation of the transducers rotated by 180° and an average taken between the two sets. In this paper results of the measurements will be presented and discussed. [Work supported by NASA Langley.]
The use of the Wigner distribution to identify structure-borne noise components
Authors: Bolton J. S. , Wahl T. J.
Published: October 2005

The Wigner distribution (W.D.) may be used to examine the time-frequency structure of a time history: e.g., to give an indication of signal arrival time versus frequency. The W.D. has recently found application in the study of wave scattering and in speech analysis. In this paper the use of the W.D. in structural acoustic problems will be illustrated. In a typical structure, vibrational energy is conveyed by several wave types simultaneously: e.g., flexural, torsional, longitudinal. Each wave type is characterized by a dispersion relation that may be interpreted in terms of phase speed as a function of frequency. In this paper it will be shown that the W.D. may be applied to structural impulse responses to reveal the dispersion relations of the wave types carrying significant energy between two points on a structure. Insofar as the dispersion relations may be associated with particular wave types, the W.D. may be used as the basis of an experimental procedure to identify the wave types present in a structure. Knowledge of this type is usually required to design optimum noise control treatments. Example calculations based on wave propagation in fluid-loaded plates and beams will be used to illustrate the proposed procedure.
Acoustic characteristics of confined jets. Part 1: Theory and numerical calculations
Authors: Ng Kam W. , Stepanishen Peter R.
Published: October 2005

A theoretical model was developed to study the wall pressure and vibratory motion of an elastic pipe which is excited by a confined turbulent jet flow resulting from fluid flow through orifices in the pipe. Based on flow field measurements, the blocked surface pressure was calculated using Lighthill's method, and then used to drive the fluid-filled shell. The wall pressure and pipe wall acceleration were determined by solving the coupled fluid-solid interaction problem. The wall pressure was obained by summing the blocked surface pressure and the pressure due to the wall vibration. An amplitude-modulated convecting wave field was used to simulate the moving acoustic sources of the jet. The random nature of the turbulent jet was incorporated into the analytical model. Specifically, the acoustic pressure was assumed to result from hydrodynamic pressure fluctuations which are uncorrelated in the radial direction, but correlated in the axial direction near the jet exit. The uncorrelated pressure fluctuations in the radial direction reflect the random motion of the turbulent jet, whereas the correlated pressure fluctuations in the axial direction reflect the motion of the large-scale coherent structures near the jet exit. It has been demonstrated that the noise model is capable of relating the flow field and the acoustic field of confined jet flows. [Work supported by ONT and ONR.]
Acoustic characteristics of confined jets. Part 2: Measurements
Authors: Ng Kam W. , Stepanishen Peter R.
Published: October 2005

The flow and acoustic characteristics of confined jets were measured by a laser Doppler velocimeter, flush-mounted hydrophones, and accelerometers. Unrestricted pipe flow and flows restricted by various orifices were tested for a wide range of velocities to simulate the flow in piping systems. Wall pressure data showed that the noise levels vary with the pipe's axial location and the peak noise is located in the vicinity of the end of the jet potential core. Correlations of wall pressure fluctuations with jet velocity showed a velocity to the 3.7th to 5.0th power relationship. A nondimensional wall pressure spectrum was established for the various confined jets by the Strouhal relationship, where the length scale is the jet hydraulic diameter. This jet pressure spectrum agrees well with the wall pressure spectrum of a turbulent boundary layer above a rigid plane. Correlations of wall pressure fluctuations and pipe wall acceleration signals showed that jet flows generate more deterministic features than pipe flow. The coherence functions of the wall pressure and pipe wall acceleration signals are relatively high near the exit of the jet. The high coherence is probably due to the large-scale coherent structures. Experimental results for wall pressure and acceleration compared reasonably well with the theoretical model for a wide range of parameters of interest. [Work supported by ONT and ONR.]
Remote sensing of the ocean bottom using the vertical directionality of the ambient noise in the water column
Authors: Buckingham Michael J.
Published: October 2005

The vertical directionality of ambient noise in the shallow ocean overlying a fast, fluid sediment is a stable feature of the noise field. It is controlled by the reflection properties of the bottom, most notably the fact that the water/sediment interface shows a critical grazing angle αc. Noise rays that are incident on the bottom at grazing angles greater than αc penetrate the interface and are lost to the water column, whereas rays with shallower grazing angles are totally internally reflected. The latter remain trapped in the channel, and contribute to the noise field. Thus, the noise field shows a symmetrical peak in the horizontal whose angular width is 2αc. Measurements of the vertical directionality of the ambient noise have been made at six sites around the U.K. coast using air-deployed vertical line arrays. From these data, estimates of the critical grazing angle have been obtained. Since the sound speed in the water column was also known from AXBT data, it was possible to infer from the measured values of αc the sound speed in the sediment. A comparison of the sediment sound speed obtained from the new noise technique with the results obtained by an independent survey using conventional seismic methods shows excellent agreement.
Ice edge ambient noise
Authors: Johannessen Ola M. , Sagen Hanne , Starke Kenneth V. , Engelsen Ingjald , Payne Susan
Published: October 2005

Ambient noise data along with oceanographic, meteorological, and remote sensing data were collected during the Marginal Ice Zone Experiment in March and April 1987 in the Greenland Sea. The experiment was designed to study how ambient noise was generated by ice kinematics, ice edge eddies, and wave propagation into the ice pack. Sonobuoys were deployed in the water off the ice edge and in the adjacent ice-field where eddies, jets, and surface waves were present. SAR images of the area were obtained during the ambient noise recordings and provided important information such as position of the ice edge relative to the sonobuoys. Advanced image processing enabled ice classification, and estimates of ice concentration and floe size distribution. These parameters provided information about how ice can influence the ambient noise level and frequency distribution. Procedures to enhance wave signature in the SAR images were used to analyze the wave pattern. Correlation between SAR and ambient noise data support the hypothesis that eddies and jets represent noise level anomalies along the ice edge.
Simulating and processing the Arctic acoustics due to ice dynamics
Authors: Pomalaza-Raez C. A. , Shanan S. S. , Shen H. H.
Published: October 2005

Under sea-ice noise, in particular that produced by ice floes in the Arctic region, is studied by means of a model simulation and the development of signal processing techniques for its measurement and estimation. This noise is due to the interaction among ice floes that produces non-Gaussian noise in time and frequency. Based on previous studies, a Gaussian shape acoustic wave pressure generated by a single collision is assumed. The random occurrence of the ice collision process is modeled as a Poisson sequence of impulses. Different sonar array spectrum estimation techniques [Fourier, autoregressive (AR), and minimum variance (MV)] are analyzed for the processing of the resulting acoustic signal. It is found that the minimum variance spectral estimation technique is the overall best for this type of signal for a wide range of the model parameters. Previously reported studies have often used the periodogram technique that as shown here usually gives poor results.
Auditory filter shapes at low frequencies
Authors: Peters Robert W. , Moore Brian C. J.
Published: October 2005

Auditory filter shapes were measured in normally hearing subjects for center frequencies (fc) of 100, 200, 400, and 800 Hz using the notched-noise method [R. D. Patterson and I. Nimmo-Smith, J. Acoust. Soc. Am. 67, 229–245 (1980)]. Two noise bands, each 0.4fc wide, were used; they were placed both symmetrically and asymmetrically about the signal frequency, to allow the measurement of filter asymmetry. The overall noise level was always 80 dB SPL Stimuli were delivered monaurally using Sennheiser HD424 earphones. Except for fc = 100 Hz, the auditory filters were asymmetric, the upper skirt being steeper than the lower skirt. At 100 Hz the filters were more symmetric, or showed an asymmetry in the opposite direction. This can probably be attributed to the reduced effectiveness of the lower noise band due to the transmission characteristics of the outer and middle ear. The equivalent rectangular bandwidths of the filters had average values of approximately 29, 42, 74, and 160 Hz for values of fc of 100, 200, 400, and 800 Hz, respectively. The signal-to-masker ratio at the output of the filter required to achieve threshold tended to increase with decreasing fc.
Review of ISO and ANSI standards for the determination of sound power levels of noise sources using sound intensity measurements
Authors: Crocker Malcolm J.
Published: October 2005

Sound intensity measurements can now be used to determine accurately the in situ sound power of machinery noise sources in the presence of high levels of background noise. Meetings of working group ISO/TC43/SC1/WG25 began in 1982 and a first draft standard was produced in late 1985. Meetings of working group ANSI S12-21 began in 1983 and produced first draft of a standard in 1984. The ANSI draft standard was circulated for balloting as a standard in 1987, and the ISO third draft was circulated in 1988. Although the ISO and ANSI drafts are similar, there are some differences. The ISO draft allows precision, engineering, and survey grade determinations and requires four indicators to be measured to decide the grade achieved. The ANSI draft only allows engineering determinations of sound power. The ISO draft only allows fixed point measurements, while the ANSI draft allows either fixed point or scanning measurements of intensity on a surface enclosing the source. Last year, 17 laboratories in North America took part in a round robin using the ANSI draft.
Implementation of a second generation sound power test for production testing of earthmoving equipment
Authors: Tweed Lorne W.
Published: October 2005

Caterpillar has developed an automated sound power measurement system that measures the noise of construction equipment before it leaves the assembly plant. This paper describes the test system and gives the results of verification tests conducted at various manufacturing plants around the world. The new system allows Caterpillar to quickly and accurately acquire the data necessary to ensure that their products meet noise requirements.
Demonstrations of nonlinear oscillators, parametric excitation, and solitons
Authors: Keolian Robert
Published: October 2005

The peculiar behavior of nonlinear oscillations will be demonstrated with a series of experiments selected from those shown previously in Austin [J. Acoust. Soc. Am. Suppl. 1 77, S35 (1985)]: (1) A stretched rubber band, driven by a loudspeaker, exhibits hysteresis due to its bent resonance curve. (2) A doubly bent resonance curve and hysteresis are exhibited by a parametrically driven pendulum bouncing against stops. (3) A hanging chain undergoes quasiperiodically modulated vibrations, where the modulations have a frequency independent of that of the drive. (4) A parametrically driven rigid pendulum will defy gravity by standing on end and oscillating upside down. (5) Standing waves on a trough of water will be parametrically driven, as seen by Michael Faraday. (6) A nonpropagating soliton [Phys. Rev. Lett. 52, 1421 (1984)] will be shown in a trough of water, and two of these solitons will oscillate about each other.
A simple apparatus for the acoustic levitation of a drop in a liquid
Authors: Apfel Robert E.
Published: October 2005

A simple apparatus consisting of a piezoelectric disc, beaker, function generator, audio amplifier, current probe, and oscilloscope is sufficient. to demonstrate the acoustic levitation of a liquid drop in an immiscible host liquid. Applications of acoustic levitation, which include measuring the tensile strength of liquids, sound velocity, interfacial tension, and other properties, will be discussed. [This was has been supported by the Office of Naval Research.]
Simple demonstration of a thermoacoustic sound source
Authors: Hofler Thomas J. , Atchley Anthony A. , Garrett Steven L.
Published: October 2005

A simple thermoacoustic prime mover, known as the “Hofler tube,” consisting of an open-closed tube containing many G-10 fiberglass plates will be demonstrated. Sound of sufficiently large amplitude to produce streaming is generated when a temperature gradient is imposed across the thermally insulating plates. The use of helium gas rather than air as the thermodynamic working fluid provides a dramatic demonstration of the effects that sound speed and other thermal properties, such as the polytropic coefficient, have on the efficiency of acoustic power generation from the thermoacoustic process. A simple model will be provided to explain the engine behavior to a nonscientific audience.
Demonstration of computer-based sonograph display
Authors: Stuart Alan D. , Frey Glenn
Published: October 2005

A computer-based sonograph display has been developed that shows the amplitude of the frequency spectrum as a function of time. Depending on the speed and processing capabilities of the computer, real-time displays can be obtained. The data acquisition procedure developed along with the display provides a means for conducting both detailed statistical analysis of the data as well as subjecting the data to other post processing analysis.
Measurement of the sound speed in air by sing-around velocimetry
Authors: Gabrielson Thomas B.
Published: October 2005

The sing-around velocimeter [M. Greenspan and C. Tschiegg, Rev. Sci. Instrum. 28, 897–901 (1957)] is capable of great precision and is an elegant measurement technique. It is also relatively easy to implement with low-cost electronics. Besides the obvious experiments on the dependence of sound speed in gases on temperature and molecular weight, it is also possible to measure gas diffusion rates or demonstrate the adiabatic nature of acoustic oscillations. Absolute measurement of sound speed within 1% is easily done. These demonstrations were developed for a graduate-level thermodynamics course given at the Pennsylvania State University Great Valley Graduate Center.
Simultaneous SLAM imaging and tensile loading of copper films
Authors: Crone Wendy C.
Published: October 2005

Preliminary experiments on imaging the mechanical properties of copper films (1 and 5 mil thick) have been performed with the scanning laser acoustic microscope (SLAM). Assessment of material properties can be obtained through attenuation and speed measurements with the SLAM. Transmission curves for a copper film were obtained at 24 and 30 MHz to assess the effects of thickness and stiffness of the film. Predictions of optimum insonification angle were then determined for 100 MHz. Real time images of a copper film with a small crack were obtained while stretching was induced. Results are encouraging and the images display changes in the attenuation and speed in the region of the crack tip as the film is loaded. It is suspected that these changes are caused by the plastic deformation near the crack tip. Further experiments are being conducted to verify this and to measure other mechanical properties. [Advisor: John Harris. Work done in cooperation with SONOSCAN, Inc. and the Bioacoustics Research Laboratory of the University of Illinois.]
Wave attenuation in 1–3 piezoceramic composites due to electric conductivity
Authors: Bao X. Q. , Varadan Vijay K. , Varadan Vasudara V.
Published: October 2005

Piezoceramic composites can be tailored to provide propagating waves with high attenuation by introducing appropriate electrical conductivity into the materials. Analysis of 1–3 type piezoceramic composite materials is presented. The optimum value of conductivity for maximum attenuation of propagating waves along the PZT fiber direction is discussed. Numerical results for 1–3 PZT/epoxy composites with various volume fractions are shown.
Scatter in ultrasonic wave attenuation measurements caused by transducers
Authors: Paul Mary A. , Pate Anna L.
Published: October 2005

The scatter in attenuation of ultrasonic waves in aluminum was investigated with five broadband, nonfocused, immersion transducers with center frequencies of 10 and 15 MHz. Three different experimental techniques were used: two types of multiple echo techniques and a multiple thickness technique. The objective was to investigate the repeatability of the measurement for the same transducer and same method, the bias towards a particular method, and the consistency of the measurements across transducers. No bias toward a particular method was found and repeatability was good. However, the results were found to be transducer dependent. Efforts have currently begun to image the transducers in order to perform their individual characterization. This characterization will be used instead of modeling transducers as rigid pistons. The effect of transducer characterization on the consistency in attenuation measurement will be discussed. [Work supported by Center for NDE, Ames, IA.]
Use of gating technique for calibrating sound intensity probes
Authors: Krishnappa G. , Chiu V. J.
Published: October 2005

Sound intensity probe calibration in large laboratory spaces using the technique of “time gating” was investigated. In this study, both the sound source and the probes were mounted 2.45 m above the room floor and the nearest reflecting surface was 4.87 m from the measurement point. The source and the probe were separated by 1.8 m. The length of the sound pulse (chirp) and trigger delay were adjusted on an FFT analyzer to prevent the probes from sensing the reflected signal. The performance of the sound intensity probes was compared with sound intensity derived from sound pressure level measurements by a single calibrated microphone. Both the two-microphone probe and the probe incorporating direct measurement of particle velocity were examined at several angles of incidence both in the horizontal and vertical planes. The results demonstrate that the calibration of sound intensity probes can be carried out with reasonable certainty in the 300- to 6000-Hz frequency range and that the “time gating” technique has the advantage of not requiring any expensive special facilities.
Acoustic source power evaluation based on finite-difference intensity
Authors: Wei Ruey-Chang , Pate Anna L.
Published: October 2005

Radiated power of a baffled piston was investigated by numerical simulation and also by measurements in an anechoic chamber with the use of the finite-difference intensity. Several parameters involved in the acoustic power evaluation were investigated. These include: the type of the scanning surface (hemisphere and half-cube), the location of the scanning surface, source directivity (ka = 1 and ka = 10), microphone spacing, and the number and density of the measurement points. As an independent experimental check, a pressure-based, farfield method was used to evaluate the source power. The source power estimated from the finite-difference intensity was within 1-dB agreement with the results from the farfield pressure based method. As a result of this study the effects of each parameter on the accuracy can be estimated, and consequently the choice of these parameters can be made. [Work supported by NSF.]
Shifts in transverse vibration modes of elastic beams resulting from a discontinuity in beam stiffness
Authors: McClure Lawrence M. , Finch Robert D.
Published: October 2005

Vibration characteristics of elastic beams are modified by a change in stiffness due to a discontinuity. This effect was first investigated by W. T. Thompson [J. Appl. Mech., Trans. ASME 16, 203–207 (1949)]. In this paper there is a report on a study of the frequency shifts due to variations in individual parameters of a crack in a beam. A quantity termed the signature sum is defined in terms of deviation from the modal frequencies of an uncracked beam and is proposed as an index to identify the presence of a discontinuity in a beam under investigation. [Work supported by NSF.]
Generation of acoustic pulses of short duration from laser pulses on metal foils
Authors: Jiang Peng , Apfel Robert E.
Published: October 2005

To calibrate transducers in water, a laser was used as a means to generate acoustic pulses of short duration. In the experiments, samples were chosen from the available metal foils (stainless steel and aluminum) with different thicknesses. Several conclusions can be drawn from the experiments. (1) The energy density of the incident laser pulse has a strong effect, depending on the properties of sample, on the duration of the generated acoustic pulses. (2) Thermal expansion β and thermal diffusivity length L are two important parameters that affect the generated acoustic waveforms, where L = (2Dtρ)1/2 and D = K/cρρ, K is the thermal conductivity, cρ is the specific heat, ρ is the density, and tρ is the duration of a laser pulse. (3) If the thickness of a sample is comparable to the thermal diffusivity length L, it will affect the generated waveform. (4) Laser generation of acoustic pulses from metal foils may be able to be used to calibrate receiving transducers in a liquid, at least in a relative sense. [Work supported, in part, by U.S. National Institute of Health through Grant 1R01CA39374.]
Surface waves in layered structures with application to vocal-fold vibration
Authors: McGowan Richard S.
Published: October 2005

The initiation of surface waves over a layered structure, including an air channel, a thin elastic layer, an inviscid waterlike fluid, and an impedance boundary, is discussed. This structure is a rudimentary picture of the vocal folds near the edges. The initiation of surface waves at the interface between the air and elastic layer is similar to the problems of initiation of wind waves over water and the flutter of panels. Early linear analyses of surface wave initiation considered Kelvin-Helmholtz instability, a static instability, and the use of Jeffreys' sheltering coefficient as a destabilizing mechanism for a dynamic instability. Both static and dynamic instabilities are possible in vocal-fold vibration. However, the dynamic type of instability is the mechanism that usually is operable in a layered structure model of vocal-fold vibration, although Jeffreys' sheltering coefficient does not provide the correct term for negative damping. This is confirmed by the lumped element two-mass model, a very successful model for simulating some aspects of vocal-fold vibration [K. Ishizaka and J. L. Flanagan, Bell Syst. Tech. J. 51, 1233 (1968)]. The two-mass model also illustrates how to incorporate dynamic pressure loss into the layered structure approach to account for the negative stiffness. The layered structure approach has the advantage of allowing for testing of the effects of changing the mechanical properties of various histological layers on the initiation of the surface wave. [Work supported by NIH grants HD-1994, NS-13870, and NS-13617 to Haskins Laboratories.]
Critical frequencies of ribbed plates
Authors: Maidanik G. , Dickey J. , Ertel J.
Published: October 2005

The vibrational and radiative properties of panels are often cast in terms of the relationship between the two sets of properties. The relationship is expressed in terms of the radiation efficiencies of these panels. Often interest lies in the dependence of the radiation efficiency on frequency; the radiation efficiency is, therefore, usually displayed as a function of frequency. If the panel is basically a plate responding in flexure it is customary to ascertain the radiation efficiency as a function of the normalized frequency (ω/ωc), where ω is the frequency variable and ωc is defined as the frequency at which the phase velocity of the free waves, in a specified direction, on the unloaded uniform plate matches the speed of sound in the irradiated fluid. The critical frequency may have directional properties. However, if the uniform plate is isotropic, the critical frequency is independent of direction. When the plate is nonuniform; e.g., because the plate is ribbed and/or finite, the “free waves and their phase velocity” on the unloaded nonuniform plate may not correspond to those on the unloaded uniform plate. Even if these free waves admit to the definition of the critical frequency ωg this critical frequency may not be equal to ωc. If there is merit in displaying the radiation efficiency as a function of the normalized frequency, which critical frequency need be used in the normalization? The paper is a brief attempt to answer this question. The definition of the critical frequencies and their use in normalizing the frequency for displaying the radiation efficiencies of regularly ribbed plates are cited as examples.
Acoustic communication in pest mole crickets
Authors: Forrest T. G.
Published: October 2005

Mole crickets are common pests of turfgrass and pastures in the southeastern United States. The males produce species-specific calling songs that function to attract mates. Males begin calling after sunset from a burrow constructed prior to calling. The burrow's opening expands exponentially and the burrows are “tuned” during their construction. Output increases 20 dB during the tuning process. Sound fields are hemispherical. Power output ranges from 4 to 20 μW and is dependent upon the size of the male and the moisture of the soil surrounding the burrow. Flying females respond to the calling song and land near calling males. Males calling in an outdoor arena were highly variable in the number of individuals attracted to their calling songs. Intensity differences among the males was the major determinant in the response of females to males in the arena. The differential response to calling males can be explained using a simple model of pressure fields surrounding two sources.
Acoustical peak identification system (APIS): An acoustical technique for distinguishing between European and Africanized honeybees
Authors: Kerr Howard T. , Buchanan M. E.
Published: October 2005

A simple method has been developed to distinguish between European and Africanized honeybees on the basis of differences in the spectral content of sounds made by worker bees in flight. The spectral content of the flight sounds for each subspecies may generally be correlated to characteristic taxonomial features (i.e., wing size, body weight, thorax dimensions, etc.) and physical behavior (i.e., foraging, stinging, etc.). Acoustic signals from over 800 individual flying European and Africanized honeybees were collected. A time-averaged signal was generated for each specimen, and standard Fourier analysis methods were used to generate power spectral density plots. Examination of the PSD's revealed that distinguishing differences exist between the acoustical signatures of flying European honeybees and flying Africanized honeybees. Specifically, the flying European honeybee signature has a fundamental power peak in the 210- to 230-Hz frequency range whereas the flying Africanized honeybee signature has a fundamental power peak in the 260- to 280-Hz frequency range. This substantial difference is easily embodied in a variety of simple identification algorithms. A patent application was submitted for the acoustical peak identification system (APIS), and a simple, inexpensive, field-portable instrument based on acoustical signature techniques has been developed for screening identification of the Africanized subspecies of honeybees. This instrument is called “Buzz Buster” and is being marketed by B-Tec.
Cross-spectral envelope phase discrimination for FM signals
Authors: Wakefield Gregory H. , Edwards Brent W.
Published: October 2005

Previous measures of cross-spectral envelope phase sensitivity have used amplitude-modulated sinusoidal carriers. To the extent that these measures reflect the fidelity of the auditory signal representation of complex signals, it should be possible to predict phase disparity thresholds for arbitrary classes of signals. Modulation phase discrimination functions were obtained for sinusoidal FM carriers at 500 and 2000 Hz. For a 0-deg phase disparity between the modulators of the standard, sensitivity to a disparity in the phase of FM modulation is monotonically related to the product of modulation frequency and modulation index over the range of modulation frequencies studied (8–64 Hz). A simple model of this discrimination task assumes that FM signals are converted into AM signals through bandpass filtering at the auditory periphery. This model was tested by demodulating the FM signals through auditory filters tuned to 500 and 2000 Hz. Thresholds obtained for these “FM-equivalent” AM signals were nearly an order of magnitude smaller than the original thresholds and it was necessary to “de-tune” the auditory filters (5- to 10-dB slopes) to fit the FM data. [This research was supported by a grant from the AFOSR.]
Signal threshold in frequency-modulated (FM) noise bands as a function of the coherence of modulation
Authors: Grose J. H. , Hall J. W.
Published: October 2005

In a recent paper reporting the absence of a co-(frequency)-modulation masking release for FM maskers, it was noted that thresholds were lower in maskers comprised of comodulated FM tones than of noncomodulated FM tones [G. S. Schooneveldt and B. C. J. Moore, J. Acoust. Soc. Am. 83, 2290–2292 (1988)]. This was interpreted as being due to a within-channel beating cue. The present study also observed a noncomodulated-comodulated difference but in conditions designed to minimize such a cue. In a baseline condition, detection of a signal was measured in the presence of an on-signal FM noise band. Two flanking FM bands were then added in four configurations relative to the on-signal band: (1) comodulated in both FM and amplitude modulation (AM); (2) comodulated in FM but noncomodulated in AM; (3) noncomodulated in FM but comodulated in AM; and (4) noncomodulated in both FM and AM. The paradigm was tested with sinusoidal and random modulation rates, different depths of modulation and both pure-tone and FM noise band signals. Thresholds for most conditions were raised relative to the respective baseline. However, for both the comodulated and noncomodulated AM conditions, thresholds were usually reduced by the transition from noncomodulated to comodulated FM. [Research supported by AFOSR.]
Gaining insight into the representational unit for spoken words with a naming task
Authors: Gagnon Deborah A. , Sawusch James R.
Published: October 2005

Theoretical proposals for the representational unit used in recognizing spoken words include the phoneme, allophone, and position-specific phoneme. The present experiment was devised to differentiate among these proposals. Subjects heard natural CVC stimuli in prime-target pairs and named the second item (target) as quickly as possible. The phonetic overlap between prime and target was varied to create five different intrapair relations such that the expected pattern of priming effects across the set of relations was different for each of the three phonetic representations. The obtained pattern is inconsistent with an abstract phonemic unit and points to either a position-specific phonemic or allophonic unit. This pattern was found for both word and nonword stimuli. Thus these priming results appear to tap the recognition process prior to lexical activation. Priming effects were eliminated when stimuli within a prime-target pair were produced by different voices. The implications of the findings for refining models of spoken word recognition will be discussed. [Work supported by NINCDS.]
Interword coarticulation modeling for continuous speech recognition
Authors: Hwang Mei-Yuh , Hon Hsiao-Wuen , Lee Kai-Fu
Published: October 2005

In large-vocabulary continuous speech recognition, subword units must be used for practical reasons. Context-dependent phone models have become a very successful class of subword units. These phone-sized models take into account the neighboring phonetic contexts, which strongly affect the realization of a phone. However, previous approaches have only considered intraword coarticulation, and have ignored interword coarticulation, which is very important in continuous speech, especially for short function words like “the” and “a.” This study extends triphone-based modeling to interword coarticulation modeling. A simple extension of triphones is problematic due to the sharply growing number of triphones. In order to contain this growth, a maximum-likelihood clustering procedure was introduced to reduce 7057 intraword and interword triphones to 1000 generalized triphones. Interword generalized triphones were incorporated into a large-vocabulary, speaker-independent, continuous speech recognizer, SPHINX [K. F. Lee and H. W. Hon, Large Vocabulary Speaker-lndependent Continuous Speech Recognition (ICASSP, 1988)]. This improvement reduced the number of errors by as much as 44% on the 1000-word DARPA resource management task. This demonstrates the importance of interword coarticulation modeling, and the effectiveness of the methods used.
Acoustical manifestations of velopharyngeal closure during swallowing
Authors: Hamlet Sandra L. , Smith Duane M. , Jones Lewis
Published: October 2005

In normal swallowing, velopharyngeal (VP) closure transienty isolates the nasopharynx from the aerodigestive tract for a period of approximately 700 ms. Although there are intrinsic sounds generated during swallowing that can be recorded from the throat surface [Hamlet et al., J. Acoust. Soc. Am. Suppl. 1 83, S23 (1988)], VP closure is ordinarily a silent event requiring special techniques for its acoustical detection. A 500- or 1000-Hz tone is introduced into one nostril, and its presence is detected using a miniature accelerometer taped to the throat just below the angle of the mandible. During VP closure, there is attenuation of this component of the accelerometer signal recorded during swallowing. The onset of the period of attenuation corresponds to the onset of velar closure determined radiologically. The time of VP reopening can be detected with less certainty, possibly owing to resonance effects, and the position of the epiglottis and base of the tongue at that moment in some subjects. Medical applications of this procedure are discussed. [Work supported by NIH.]
Voicing epoch determination with dynamic programming
Authors: Talkin David
Published: October 2005

During voiced speech, the point of maximum flow change in each glottal cycle corresponds to the point of maximum excitation of the vocal tract. Accurate, reliable detection of this “epoch” beginning (or end) is useful for pitch synchronous analysis/synthesis in a variety of contexts. Dynamic programming has been applied to correlation function peak selection [Secrest and Doddington, ICASSP-83] and lagged waveform matching [Ney, IEEE Trans. SMC-12 (1982)] for F0 determination with excellent results, but these techniques do not yield the epoch locations. The method described in this paper applies dynamic programming to select waveform maxima directly from a short-time-energy-normalized LPC residual. The cumulative path costs are normalized by the path length. Local costs are based on peak amplitude and quality, transition costs on period and pulse similarity. The output is the set of pulse locations that globally satisfy the cost constraints over all voiced regions. Data to be presented indicate that these estimates reliably match those obtained semiautomatically from simultaneously recorded electroglottograph signals.
Interactions between nearophysiology and speech distrimination
Authors: Sinex Donal G. , McDonald Lynn P. , Mott John B.
Published: October 2005

Psychophysical approaches have provided much information about the processing of speech sounds by humans and also by laboratory animals. These studies establish the essential functions of the auditory system that must be explained and define the limits over which they operate. However, processing mechanisms cannot be discovered by psychophysical approaches. Details about mechanisms must come from neurophysiological studies. This view has guided this investigation of the processing of voice onset time (VOT), a complex acoustic cue that differentiates between consonants such as /d/ and /t/. The peripheral neural representation of VOT syllables was studied, asking which (if any) properties of the neural responses correlated with the results of psychophysical experiments conducted by Kuhl and Miller [J. Acoust. Soc. Am. 63, 905–917 (1978); 70, 340–349 (1981)]. The psychophysical findings provided a standard against which hypotheses about the representation of VOT information could be evaluated. As a result, it was possible to identify a neural mechanism in the auditory periphery that may contribute to the formation of phonetic categories based on voicing. [Work supported by NS23242 from NINCDS.]
Problems and opportunities in extending psychophysical/physiological correlation into the central nervous system
Authors: Young Eric D.
Published: October 2005

Because auditory-nerve fibers form a relatively homogeneous population, it is possible to build models that account for psychophysical performance on the basis of auditory-nerve response properties using rather direct assumptions. However, when this analysis is extended to the CNS, the problems become more complex because of the diversity of different response types and the multiplicity of parallel central pathways. At minimum, one is faced with parallel analyses of several systems, some of which may not be relevant to the psychophysical problem being analyzed. One approach has been to use natural stimuli whose behavioral significance for the animal is clear and to analyze behavioral and physiological responses to those stimuli in the same animal. Examples of successful application of this approach are bat sonar and barn-owl sound localization. Another approach is to use the properties of directionally selective spectral shaping by the pinna to define stimuli with known behavioral relevance. Examples taken from the cat cochlear nucleus will be used to illustrate the issues raised above. [Work supported by Grant NS12524 from NINCDS/NIDCD.]