bluuebunny/crossref_metadata_2025 huggingface dataset:
The Green's function of the fluid-loaded plate
Authors: Crighton D. G.
Published: October 2005

The surface response of an infinite thin elastic plate or membrane to concentrated forcing is considered under the (realistic) condition that the normalized response is specified by three parameters: (1) a ratio Ω of driving frequency to the vacuum coincidence frequency, (2) the product X of distance from the excitation point and the vacuum free wavenumber, and (3) a parameter ε characterizing fluid loading at coincidence. We use the fact that in all applications ε is small to construct matched asymptotic expansions for the Green's function covering the entire range of frequency and distance (0 < X, Ω < ∞). The method is applicable equally to line or point forcing and to plate or membrane response, significant differences being confined to the nearfield. The farfield for Ω = O (1) consists of free surface or leaky waves plus an acoustic field decaying as X1/2 at moderate X and as X3/2 at very large X, with a transition expressed by parabolic cylinder functions; the description for other Ω is obtained, but is more complicated.
Random vibration field on a plate
Authors: Waterhouse R. V.
Published: October 2005

The properties of a steady-state random, or reverberant, sound field in a reverberation chamber with stationary boundaries are fairly well understood. When the driving signal consists of a single-frequency tone. and many modes are excited, the sound field in the chamber becomes a randomly irregular interference pattern whose statistical properties follow known distributions. For example, the mean-square pressure values, suitably sampled, follow an exponential distribution, the simplest kind of gamma distribution. It is pointed out that the same gamma distributions held for the vibrational field on a thin elastic plate vibrating in flexure, under the same conditions of pure tone and multimode excitation. Knowing the distribution of the acceleration values on such a plate is of practical value as it allows one to estimate the confidence levels of the average of a limited number of sample values.
In situ determination of loss and coupling loss factors by the power injection method
Authors: Bies David Alan , Hamid Shahul
Published: October 2005

Inversion of the linear power balance equations for a two coupled plate model is used to determine the plate loss factors and the coupling loss factors in situ. To accomplish the determinations, injected power at points chosen at random was measured. To ensure effective statistical independence of modes, each plate was driven at five different points in sequence and the response of both plates in each case was determined at ten randomly chosen points. Good agreement is obtained between the predicted and measured coupling loss factors, and between the in situ loss factors and loss factors determined for each plate separately also in steady state from power injection measurements. Loss factors determined by transient decay methods are consistently lower than those determined by either steady-state method. During reverberant decay, the more lightly damped modes predominate, giving rise to an apparent loss factor which is significantly less than the steady-state loss factor determined under conditions of essentially equal energy per mode.
Effect of time varying noise on speech communication
Authors: Pearsons Karl S.
Published: October 2005

A review of research on effects of time varying noise on speech intelligibility will be presented. Investigations using recorded traffic noise and shaped noise as masking will be reviewed, as well as the use of intelligibility tests. Comparisons of Articulation Index predictions will be presented for different intelligibility tests. The importance of accurate measures of speech levels will be emphasized. The relationship between speech intelligibility and annoyance will also be discussed, using results from social surveys and laboratory tests. Research needs will also be discussed.
Sleep interference from intermittent and continuous noise exposure
Authors: Horonjeff R. D. , Teffeteller S. R.
Published: October 2005

Some effects of temporal patterns, duration, amplitude, and spectral content of noise intrusions on patterns of residential awakening are presented. Behavioral awakening measures developed in the course of a study of probabilities of awakening associated with low level nocturnal noise intrusions are discussed. Potential influences of background noise environments on the ability of noise intrusions to awaken people are also considered. Comparisons will also be made between the current data and those of prior studies.
Study of higher-order elastic and piezoelectric constants with shock-wave loading techniques
Authors: Graham R. A.
Published: October 2005

Many solids remain elastic to strains of a few percent when subjected to uniaxial strain imposed by shock loading. Nonlinear contributions are enhanced by such large elastic strains and become accessible for relatively straightforward measurement and interpretation. Impact loading techniques have proven particularly effective for measurements of second-, third- and fourth-order longitudinal piezoelectric constants as well as third- and fourth-order longitudinal elastic constants. Shock compression studies have provided independent measurements of constants, have uniquely determined certain constants and have extended ultrasonic measurements by several orders of magnitude in strain. Typical experimental investigations and their results will be summarized and compared to corresponding ultrasonic data. [This work sponsored by the U.S. Department of Energy under Contract DEAC04-76-DP00789 to Sandia Laboratories, a U.S. Department of Energy facility.]
Heterogeneous yielding and melting under shock compression
Authors: Grady D. E.
Published: October 2005

Shock compression offers a method for investigating the physical properties of solids at pressures and temperatures not readily accessible by other techniques. To correctly assess the physical phenomenon of interest, a thorough understanding of the thermodynamic and metallurgical state of the material created during shock compression is necessary. The transition to the shocked state involves a catastrophic deformation of the solid and only a limited understanding of this deformation process has been achieved. Recent studies suggest that the process of shock deformation can be heterogeneous in the sense that yielding is localized to relatively few, narrow shear zones within which the shock energy and inelastic deformation are concentrated. This concept of shock deformation can have profound consequences on the resulting shock state. Nonuniform energy deposition, strong thermal gradients, and regions of partial melt can persist for the brief period of time that the shock state is maintained, suggesting a highly nonequilibrium situation. Many of the features of shock compression and release are readily explained by a heterogeneous deformation process and apparently depend on the competing properties of thermal diffusion, melting temperature, and degree of thermal localization. [This work was supported by the U.S. Department of Energy (DOE) under contract DE-AC04-76DP00789.]
New high-frequency regeneration (HFR) techniques for voice-excited speech coders
Authors: Higgins A. , Viswanathan R. , Russell W.
Published: October 2005

In voice-excited speech coders, high-frequency information must be regenerated from the transmitted baseband by some nonlinear operation. Waveform rectification, with its well-known harmonic generation property, has traditionally been used for this purpose. Recently, Makhoul and Berouti (ICASSP '79) introduced the method of spectral folding, in which HFR is accomplished by means of aliasing the baseband spectrum. Although this method generates certain low-level tonal noises, it does not have the perceivable roughness produced by rectification and is much simpler computationally. In the present study, we have investigated several modifications to the spectral folding method with the goal of reducing or masking the tonal noises at the cost of increased computations. One modification requires randomly perturbing the nonzero samples of the spectrally folded signal, while another involves preflattening of the baseband. A third approach performs HFR in the DFT frequency domain. The paper describes these techniques and presents the results of both informal and formal speech quality evaluation of the new and existing HFR techniques. [Work sponsored by the Department of Defense.]
Lingua: A language interpreter used for demisyllable speech synthesis
Authors: Browman Catherine P.
Published: October 2005

A set of programs, collectively called Lingua, have been developed to apply rules to an input string for a speech synthesis system. Lingua is a general purpose system, in which the user specifies the basic unit size for the synthesis, the set of input characters, any set of features, and any type of rule that can be expressed in linguistic notation. Lingua was used to synthesize speech from the demisyllable inventory established by Lovins [Lovins, Macchi, and Fujimura, J. Acoust. Soc. Am. Suppl. 1 65, S130(A) (1979]. The system will be described and the resulting speech demonstrated.
Consonant intelligibility of speech produced by dyadic rule synthesis
Authors: Olive Joseph P. , Pols Louis C. W.
Published: October 2005

We measured the intelligibility of speech generated by a speech synthesis system which converts text to sound by rules. The synthesis process uses dyadic concatenation and is intended for automatic voice answerback in telephone directory assistance situations. The intelligibility of initial and final consonants in monosyllabic words was measured. For comparison two other conditions were tested: PCM-coded speech (12 bits, 10-kHz rate) and LPC-resynthesized speech 02 parameters).

The overall percentage correct score for initial and final consonants, averaged over the 33 listeners, was 93.0% and 92.8% for PCM-coded speech, 86.5% and 85.4% for LPC-resynthesized speech, and 58.2% and 73.5% for rule-synthesized speech. Each word list was preceded by two practice runs consisting of one example word for every initial or final consonant. After this very short training phase, the subjects showed no more learning during the actual word list. The voicing character of initial voiced fricatives was not well represented in the rule-synthesis system. For most other identification errors it was clear that a more optimal choice of the dyads would cause a great improvement.
Effects of source micromotion on an acoustic signal in the frequency, time, and space domains
Authors: Flanagan R. P. , Weinberg N. L.
Published: October 2005

The effects of periodic source micromotion on an acoustic signal are examined with micromotion in the vertical plane being emphasized. Single phone radial and skew source motions are investigated utilizing CW and narrow-band equispaced, equal amplitude, multitonal signals to 200 ± 12 Hz. Brief comments on array reception are included. The study, based on ray model calculations, shows that source micromotion does not appreciably affect the coherence bandwidth of the received signal but introduces a fluctuation having the period of the micromotion, Tmm, which can reduce coherence times appreciably. Spatial coherence lengths are extremely large due to the simplified ray model. Micromotion transfers power from the central peak of the power spectrum to sidebands separated from that central peak by ±1/Tmm Hz. The power in the spectral sidebands of the received signal is dependent on the signal level and the magnitude of the source micromotion. [Work supported by ONR Code 222.]
Ocean and model measurements of underwater acoustic scattering functions
Authors: Tuteur F. B. , Zapinsky A. , Zornig J. G.
Published: October 2005

A series of measurements of the joint Doppler shift and delay (the scattering function) of surface scatter have been made under controlled conditions. Two series of experiments were conducted, one in the Pacific ocean and one in the model tank facility at Yale. The measurement technique in both cases was the use of a time series of probing pulses [J. G. Zornig, J. Acoust. Soc. Am. 64, 1492–1499 (1978)] to extract fading time series data over a wide signal bandwidth. The result of an analysis of these data indicates a statistical relationship between frequency spread and relative arrival time which is not in agreement with previously reported theoretical results [F. B. Tuteur and J. F. McDonald, J. Acoust. Soc. Am. 57, 1025–1029 (1978)]. The ocean and tank data are in substantial agreement and examples of a test of the data acquisition and analysis system, using solid moving targets, are presented as confirmation of method. [Work supported by NSF and MPL, Scripps.]
Paul Boner's contribution to the design, equalization, and operation of sound reinforcement
Authors: Coffeen Robert C.
Published: October 2005

The work of Dr. C. Paul Boner, relating to sound reinforcement systems for large spaces, ranks at the top of contributions in this field during the past two decades. Those who design and operate sound reinforcement systems, as well as those who simply listen to such systems, are indebted to Paul for his far-reaching efforts.
Gothic sound for the neo-gothic chapel of Duke University
Authors: Newman Robert B. , Ferguson James G.
Published: October 2005

The Duke University Chapel, a 250-ft-long, one million cu ft neo-gothic structure, was built in 1930–32. It was finished on half of its interior surface with Akoustolith, a precast artificial sound absorbing stone. The remaining surfaces were Indiana limestone. This resulted in a mid-frequency reverberation time of about 3 s in the unoccupied space. A donor offered to give a new organ for the chapel provided the space could be made to sound the way it looks. After considerable experimentation, four coats of sealer were applied to the Akoustolith. The reverberation time was increased to over 7 s, creating an ideal environment for the new organ. The old speech reinforcement system was then hopeless as had been predicted. A new system was designed and installed. It uses column loudspeakers at each structural pier in the nave with additional column speakers serving crossing and transepts, all with appropriate time delays. Now the chapel has superb conditions for liturgical music and excellent speech intelligibility.
The University of Texas at Austin special events center: acoustics, noise control, and audio systems
Authors: Boner Charles R. , Dickensheets Kenneth R.
Published: October 2005

This paper explores the acoustic design, noise control design. and sound/audio system philosophy behind this 18 000-seat, multi-purpose arena. The paper will focus in particular on the unique manner in which the interaction between the Consultant and Building Manager helped create an ideal environment for a state-of-the-art building. A complete description of the acoustical treatments, noise control design, and audio systems and equipment will be presented.
Loudspeaker array design for a high school gymnasium
Authors: Ashley J. Robert , Cox John Charles
Published: October 2005

Boulder High School gymnasium, built in 1937 for basketball, has used two P.A. systems of unsatisfactory performance. The usual budgetary situation requires that an attempt be made to install equipment which does not include deadening of several badly reflecting surfaces. To prevent loss of intelligibility because of auditory backward inhibition, the loudspeaker array must illuminate the seating area with minimum illumination of the reflecting surfaces. An estimate of the cost of an adequate horn array quickly ruled out this approach. The work on electrically tapered linear array loudspeaker systems by the Australian, Dr. J. E. Bensen, was adapted to the design of a loudspeaker array which is electrically tapered in both horizontal and vertical directions. Measured directivity of this array will be presented. Performance of the installation will be discussed.
Sound reinforcement for the Pontiac Silverdome
Authors: Coffeen Robert C.
Published: October 2005

After several years of use, the sound reinforcement system for the Pontiac Silverdome has demonstrated its capabilities for football, basketball, and other uses. The Pontiac Silverdome has a volume of approximately 49 million cu ft, and the unoccupied mid-frequency reverberation period is approximately 9 s. The conditions provide a difficult environment in regard to the provision of suitable sound reinforcement.
Regional air pollution study acoustic radar analysis program
Authors: Waldron T. L. , McElroy J. L.
Published: October 2005

An acoustic radar (sodar) was operated in urban St. Louis from February 1975 through May 1977 as part of the Regional Air Pollution Study (RAPS). Comprehensive analysis procedures were developed to catalogue the acoustic data and supporting meteorological data in a generalized format but with sufficient detail to be utilized for various RAPS studies. The described analysis program includes assignment of one of thirty documented echo pattern classifications, determination of base and top heights for up to three layers each half hour, and echo description codes for intensity, height tendency, and boundary appearance. Meteorological data input includes 24-h narrative summaries, identification of frontal passages, 3-h surface data, and 12-h 850-mb data. A typical “plain language” output is presented. Slow ascent radiosondes were released at the study site every 6 h during the entire operational period allowing extensive comparison between the vertical profile data and the acoustic echo pattern types. Results are presented for one stable and one unstable classification.
Acoustic propagation in a thermally inhomogeneous atmosphere
Authors: Van Moorhem W. K. , Butterworth James R.
Published: October 2005

A series of propagation experiments have been carried out at distances between 14 and 1 mile on a dry lake bed in western Utah. Detailed measurements were made of the vertical temperature profile within about 6 m of the ground along with some low-level wind-speed measurements. Although propagation both upwind and downwind was considered, the strong temperature gradients near the ground would have resulted in the formation of an acoustic shadow in all cases considered. The results obtained, however, show a clear correlation with wind direction, similar to the upwind and downwind cases of earlier investigators. It appears that winds above the level measured here play a significant role in long range propagation. [Work supported by NSF.]
Farfield distortion of transient waveforms propagating through the atmosphere
Authors: Pierce Allan D.
Published: October 2005

It has long been known [E. F. Cox, in Encyclopedia of Physics, (Springer-Verlag, Berlin, 1957), Vol. 48, pp. 469, 472] that transient infrasound pulses, received at horizontal distances of 20 km or larger from their source, exhibit substantial changes in signature (e.g., more cycles) from those received closer in. Nonlinear effects, relaxation effects, and ground impedance effects are shown to be inadequate to account for this distortion. The author's explanation rests on the presence of atmospheric turbulence and is similar to the wavefront folding mechanism [J. Acoust. Soc. Am. 49, 906–924 (1969)] previously invoked to explain the anomalous rise times of sonic booms. The turbulent winds cause any single geometrical acoustics ray predicted for a perfectly stratified atmosphere to be replaced by a family of closely spaced rays connecting source and listener. Diffraction washes out turbulent scales less than a representative wavelength divided by 2 π. The further the listener, the more such rays and the more cycles in the waveform. It is suggested that an analysis of the distorted waveform will yield a parameter (analogous to Crow's t c) that gives a gross integrated average measure of the turbulence along the nominal ray path.
Model studies of aircraft sideline noise
Authors: Chessell C. I.
Published: October 2005

The prediction of aircraft sideline noise from overhead data requires a quantitative understanding of the excess attenuation introduced by the presence of the ground between the aircraft and observer. This attenuation becomes particularly important when the aircraft subtends low elevation angles relative to the observer. A number of gross empirical models have been developed for this phenomenon based on limited experimental data. In this paper theoretical predictions of excess ground attenuation are presented. The fibrous absorbent material model is used to represent the finite acoustic impedance of the surface. Excess ground attenuation as a function of range, elevation angle, surface impedance, and aircraft source spectrum is studied and the theoretical results compared with experimental measurements of sideline noise.
Use of the Prony method in reflection coefficient measurements of acoustic panels
Authors: Trivett D. H. , Robinson A. Z.
Published: October 2005

A modified Prony method is presented for measuring steady-state reflection coefficients of acoustic panels. The method extrapolates the steady-state amplitude from the transient portion of the signal allowing time limited measurements. This method is applied to measurements of square panels 76 cm on an edge and 0.95 cm thick of steel, aluminum, and Lucite in the frequency range of 3–10 kHz. The signals were time limited to 200 μ (0.6–2.0 λ) by the arrival of the diffracted signal from the panel edges. Results are compared with theoretical values and indicate that the method is capable of making measurements subject to ambient noise. [Work supported by Target Strength Reduction Program managed by DTNSRDC of NAVSEA 037.]
On the compressional damping mechanism in the free impedance response of damped three-layer beams
Authors: Douglas B. E.
Published: October 2005

The transverse free mechanical impedance response of an elastic-viscoelastic-elastic beam incorporating the compressional damping mechanism is considered. The work of Douglas and Yang is extended to include shear deformation and rotary inertia in the elastic layers. The effects of nearly incompressional viscoelastic damping cores on the compressional frequency and hence on the spectral range of damping effectiveness for the composite is also discussed. Results of the analysis are shown to compare favorably with experimental results for a damped three-layer beam which was optimized for compressional damping and in which the influence of the shear damping mechanism was intentionally minimized.
Determination of sound pressure distributions in liquid-filled, elastic and viscoelastic tubes by finite-element method
Authors: Schroeder E. A. , Ho L. T.
Published: October 2005

Based on the finite-element approach, the elastic tube was represented by the conical shell elements CONEAX, while the fluid was modeled by the solid elements TRAPAX. Matrix equations at grid points for the displacement vectors in the solid and sound pressure field in the fluid were coupled at the fluid-structure interface. Constraints were applied and material parameters were chosen so that the axial displacements at grid points in the fluid would correspond to sound pressures that satisfy the wave equations. The coupled equations were solved for sound pressures, using structure computer program NASTRAN. Excellent agreement was obtained between the calculated and experimental results of low-frequency sound pressure distributions in an elastic tube. For the case of a liquid-filled, rigid tube lined internally with viscoelastic material, both the fluid and the liner elements were represented by the trapezoidal ring elements TRAPRG. Good correlation was observed qualitatively between the calculated and experimental sound attenuation in a viscoelastic tube. [Work supported by Naval Sea Systems Command.]
Calibration procedure and error analysis for a violin radiation measuring system
Authors: Arnold Eric B. , Weinreich Gabriel
Published: October 2005

The system referred to in the preceding paper involves measurement of acoustic pressure, both in amplitude and in phase, on two concentric spheres of known radii. Among possible sources of error are: the finite number of measurements; inaccuracy in microphone positioning; scattering by the moving boom system; electrical and acoustical noise in the microphone system; spurious phase shifts and gain inequalities in the microphone and amplifier channels; timing errors and overtone sensitivity of the phase-sensitive detectors; offsets and quantizing errors in the analog-to-digital converter; and numerical computation errors. Effects due to the nonideal nature of the anechoic chamber are in a different category, since our system measures the reflected wave directory. [Work supported by NSF.]
Measured reproducibility of clarinet spectra
Authors: Benade A. H. , Larson C. O.
Published: October 2005

Published spectra show little consistency beyond a tendency toward strong odd partials. Neglect of radiation pattern and wave-statistics fluctuations in rooms, join with inadequate specification of the player's task to cause this variability. We have studied 0.5 s alternating C4, D4 tones lasting about 35-s total at mezzoforte level (reed just beginning to beat), played on six clarinets, A, B♭ (three), C, E♭ All instruments were optimized to similar criteria over the past decade by one of us (AHB) who also made each its own mouthpiece (the bores were dissimilar). The instruments all have been used by major players. The player (AHB) walked about while playing (0.75 m/s), as did the two persons carrying the recording microphones, in a room V = 8000m3, T60 = 1.2 s. Source and mike position changes, plus mode perturbation effects from three people, assure the equivalent of at least 75 statistically independent data points for each component of each tone. The SPL for the first five harmonics averaged over all twelve tones are 50, 22.6, 48.8, 27.0, 48.3 dB (σ = 2 dB). Room fluctuations are within ±1 dB (95% confidence). Most of the remaining variation comes from interinstrument differences and not player/instrument instabilities. These results are consistent with a preliminary experiment analyzed by Karla Brasaemle. [Work assisted by NSF.]
A functional model of a simplified clarinet
Authors: Stewart S. E. , Strong W. J.
Published: October 2005

A functional model (computer simulation) of a simplified clarinet has been implemented on a digital computer. The simplified clarinet consists of a standard clarinet mouthpiece and reed attached to a straight cylindrical tube without tone holes. The tube and mouthpiece are represented in the model by a lumped element approximation to a transmission line. Application of Kirchoff's circuit laws to this circuit gives a coupled set of differential equations which were solved numerically on a digital computer to yield volume velocities and pressures in the mouthpiece and tube. The pressure in the mouthpiece drives the reed which is represented in the model as a tapered bar clamped at one end. The partial differential equation describing vibrations of such a bar was solved numerically to obtain the size and shape of the reed aperture. The reed aperture area governs the volume velocity into the tube which in turn drives the air column vibrations. The model exhibits self-sustained oscillations, threshold blowing pressures, and “lipping” of the tone. The spectra of the mouthpiece and radiated pressures are in general agreement with actual clarinet spectra. Some interesting features of the model are the inclusion of a frequency-dependent viscous loss in the tube and a dependence of the aperture volume velocity on the initial or rest opening of the aperture.
Temperature-induced length and tension variations affecting the pitch of a stretched string
Authors: Kelly Robert E.
Published: October 2005

The pitch variation of a stretched string is analyzed in terms of length and tension perturbations caused by temperature. In particular, it is shown that tension changes due to differential expansion between the string and its frame usually dominate the effects caused by an explicit length deviation. Numerical examples are given for various combinations of string and frame compositions. The corresponding problem for the wind instruments is briefly considered, including the typical viewpoint of performing musicians.
Contrasting sounds in the upper male voice
Authors: Smith Lloyd A.
Published: October 2005

Four sounds were contrasted in the upper male voice. The sounds were identified as follows: (1) falsetto; (2) head tone; (3) pharyngeal voice; (4) operatic head voice. All sounds were sung by a tenor on the vowel /a/ at a pitch level of A4, 415 Hz. Spectrographic analyses were performed to determine what physiological relationships might be inferred among the sounds. The length of time the singer was able to sustain each sound was tested in order to gain information concerning the relative air flows. The results show that the pharyngeal voice and operatic voice have much more energy in the high partials and have much lower rate of air flow. This evidence indicates that these two sounds are characterized by much more complete closure of the glottis than is exhibited in the other two sounds. It is concluded that the four sounds are produced by only two different laryngeal adjustments. Acoustical differences accounting for differentiation of sounds produced by the same laryngeal setting are discussed. A recommendation is made concerning the pedagogical use of registers and suggestions are made for further research.
Optional modules for a flexible musical acoustics course
Authors: Hall Donald E.
Published: October 2005

Musical acoustics courses draw students with a wide range of backgrounds, from nonmusicians to graduate music majors. Within either group there is a variety of topical interests—one instrument or another, room acoustics, hi-fi, harmonic theory, perception, etc. To meet the needs of such a diverse group, I have been offering a course with a spiral organization that branches into roughly a dozen optional modules, of which each student is to choose two or three for detailed study. I will describe the course outline and how the module assignments are handled. Student evaluations of this approach are very favorable, and have also given useful feedback for improving the scheme.
Statistical independence of a series of ambient noise measurements
Authors: Driscoll D. A. , Webster W. J.
Published: October 2005

The autocorrelation of a series of noise parameters (Leq, L10, L50, or L90) was examined. The noise parameters were derived from 15-min records of ambient noise collected at the same hour (0000, 0600, or 1800 h) on each of 100 (predominantly consecutive) days at a rural site. The same analysis was also performed for a suburban and a quiet, urban, residential site. The first zero crossing (indicating statistical independence) occurs at 9–13 days for the rural site. A run test for randomness (0.05 level of significance) was also used. The random hypothesis consistently failed for the rural site, showing that consecutive days do not produce a random string of data. It is shown that for an efficient ambient survey, samples should be separated by at least three days for rural sites, but that consecutive day samples are normally satisfactory for urban and suburban sites.
The influence of own-phonation on parts of the central auditory pathway in the squirrel monkey
Authors: Müller-Preuss P.
Published: October 2005

The reactivity of the auditory cortex and the auditory midbrain to self-produced and loudspeaker-transmitted calls were investigated in order to study the relationships between brain structures which are involved in the production of vocalizations and brain structures which take part in auditory processing. Responses of single cells were extracellularity recorded during stimulation with self-produced vocalizations (elicited mainly through electrical brain stimulation or uttered partially spontaneously), tape-recorded playback of those self-produced vocalizations and other species-specific vocalizations. Over 50% of the cortical cells which respond to loudspeaker transmitted calls, gave no response to self-produced vocalizations or a significantly weaker one. In contrast, most of the midbrain cells tested show no difference in their reactions to self-produced and loudspeaker transmitted calls. The response patterns of units which respond to self-produced cells do not differentiate between self-produced and playback vocalizations. It is concluded that brain structures which are activated through phonation can have an inhibitory influence on central auditory structures and that this influence takes place at a higher level than the auditory midbrain.
Discrimination of brief tones by humans with temporal lobe damage
Authors: Cranford J. L. , Stream R. W.
Published: October 2005

A number of recent Russian investigations [A. V. Baru and T. A. Karaseva, The Brain and Hearing, Consultants Bureau, New York, (1972)] reported that dogs and humans with large auditory cortex lesions, exhibit significant increases in both their absolute detection thresholds as well as their frequency difference limens for tonal signals which are shorter than 16 ms in duration. In contrast, more recent studies [J. L. Cranford, J. Acoust. Soc. Am. 65, 1573–1575 (1979)] with cats suggest that the cortex, rather than being essential for detecting the simple presence of brief tones, may be more important for discriminating qualitative differences in such sounds. While having normal absolute detection thresholds for brief tone pulses, cats with auditory cortex lesions, in comparison to unoperated controls, do exhibit elevated frequency difference limens. In order to investigate the inter-species generality of these new animal findings, we recently presented the same series of brief tone tests to two human patients with temporal lobe lesions (one left-sided CVA, and one right-sided glioblastoma case). The results with the two patients are remarkably similar to those obtained with cats. Both patients exhibited normal absolute detection thresholds for brief tones in combination with significantly elevated frequency difference limens. [Work supported by Deafness Research Foundation and NINCDS.]
Spectral basis of human frequency-following response to the “missing fundamental”
Authors: Greenberg Steven , Marsh James T.
Published: October 2005

Psychophysical studies of the “dominance” and “existence” regions of the “residue” underscore the importance of peripheral frequency analysis in the perception of pitch. However, the means by which the peripheral analysis of individual frequency components is transformed into a unitary percept dominated by the pitch of the residue, remains obscure. Farfield, vertex-derived. frequency-following responses (FFR), representing the integrated synchronized activity of phase-sensitive neurons most likely situated in the inferior colliculus, were recorded during presentation of multicomponent (n = 2, 3, 4), harmonically related tone bursts. The frequency spectrum and waveform periodicity of FFR to low-order harmonics (harmonic ranks 3–5) are clearly dominated by a frequency corresponding to the “missing fundamental”. The amount of energy in this frequency band diminishes considerably with increasing harmonic rank, becoming negligible for harmonics above the thirteenth. The existence of a parallel between psychophysical and FFR measures of pitch strength raises the possibility that in the brainstem auditory pathway, the “transmission code” for residue pitch is based on neural periodicity.
Dorsal cochlear nucleus (DCN) and its contributions to the brain stem electric response (BSER)
Authors: Markuszka Jack , Ryan Allen F.
Published: October 2005

This report focuses on the contributions of the DCN to the BSER as part of a larger study of the origins and clinical applications of the BSER. Since their initial description, the successive waves of the BSER were thought to be related to the successive nuclei of the brain stem auditory pathway. Although a strict correspondence appears not to be the case, the exact nature of the physiology and underlying anatomy of the BSER is very much in doubt. Restricted lesions of the cochlear nucleus were utilized to explore the role of various elements within the nucleus in the generation of the BSER, as well as to assess the sensitivity of the BSER to restricted lesions of the central auditory pathway. DCN was selected as the first independent variable because it is easily accessible for aspiration lesions. The results suggest that (1) an overall reduction of the BSER occurs as a result of general trauma; (2) waves I, II, and V are not otherwise affected by destruction of DCN; (3) waves III and IV are altered after DCN lesions. The nature of the changes, their clinical implications, and future directions of our research will be discussed. [Supported by the Research Service of the Veterans Administration.]
Detection of amplitude modulated noise by parakeets
Authors: Dooling R. , Searcy M.
Published: October 2005

The threshold for amplitude modulated broad-band noise was measured in parakeets using avoidance conditioning and a modified method of limits procedure. Amplitude modulation thresholds were measured at ten frequencies between 5 and 2560 Hz. Below 40 Hz, modulation thresholds were constant at about 9% modulation depth. Above 80 Hz, the modulation threshold increased with modulation frequency at the rate of about 4 dB/octave. The 3-dB down point of this function is at approximately 150 Hz. These results are compared with data obtained from human listeners using the same experimental apparatus. [Work supported by NIMH Grant ♯MH31165.]
New techniques for automatic speaker verification using telephone speech
Authors: Furui S.
Published: October 2005

This paper describes new techniques for automatic speaker verification using telephone speech. The operation of the system is based on a set of functions of time obtained from acoustic analysis of a fixed, sentence-long utterance. These time functions are expanded by orthogonal polynomial representations and compared with stored reference functions. After dynamic time warping, a decision is made to accept or reject an identity claim. Three sets of experimental utterances were used for the evaluation of the system. The first and second sets each comprises 50 utterances by 10 customers each and a single utterance by 40 imposters recorded over a conventional telephone connection. The third set comprises 26 utterances by 21 customers each and a single utterance by 55 imposters recorded over a high quality microphone. The first and third sets were uttered by male speakers, whereas the second set was uttered by female speakers. Reference functions and decision thresholds were updated for each customer. The evaluation indicated mean error rates of 0.19%, 0.36%, and 0.77% for each utterance set, respectively.
A conversational-mode airline information and reservation system using speech input and output
Authors: Levinson S. E. , Shipley K. L.
Published: October 2005

We describe a conversational-mode speech understanding system which enables its user to make airline reservations and obtain timetable information through a spoken dialog. The system is structured as a three level hierarchy consisting of an acoustic word recognizer, a syntax analyzer, and a semantic processor. The semantic level controls an audio response system making two-way speech communication possible. The system is highly robust and operates on line in a few times real time on a laboratory minicomputer. The speech communication channel is a standard telephone set connected to the computer by an ordinary dialed-up line.
Interpretations of speech and noise characteristics of NTID learning centers
Authors: Webster J. C.
Published: October 2005

The visual and acoustic design of four types of learning centers will be discussed. Levels of background noise and teachers voice levels in four classrooms will be interpreted in terms of expected speech discrimination. A flow chart relating degrees of hearing impairment and acceptable background noise levels for successful hearing aid use will be presented for comment.
Open-plan offices may be hazardous to persons with impaired hearing
Authors: Leshowitz B.
Published: October 2005

The increasingly popular open-plan design of office space defines work zones not by room partitions, but by free-standing barriers and specially constructed acoustical environments. The key ingredient in achieving privacy, while maintaining the desired flexibility of the open-plan office, is the insertion of low-level masking noise throughout the space. While the level chosen for the background noise depends on several architectural and personal factors, broadband noise at levels up to 52 dBA is acceptable, at least to most people with normal hearing (ASTM, 1976). But what about the substantial segment of the population that is known to have a significant hearing problem? It is well known, for example, that a major limitation of the listener with sensorineural hearing damage is the inability to understand audible speech presented against a background of competing sound. For the impaired listener, the ratio of speech to background level (or S/N) must be increased by about 10 dB over that measured for normally hearing individuals. It thus appears that the modern design of office space, emphasizing acoustical sound insulation, is totally incompatible with the auditory abilities of many potential, especially elderly, users of these enclosures. In the present paper the limitations of the open office plan for handicapped listeners are examined; where appropriate, design criteria are recommended.
Consumer needs of the hearing impaired: The European experience and its applicability to North America
Authors: Tobin Henry
Published: October 2005

Several European nations have established a practice of building electronic aids for hearing-impaired listeners into public meeting rooms, churches, and theatres. The acceptance of these systems by their users and by the various public and private agencies is assessed. The provision of such listening systems is another way for acoustical designers to give consideration to the hearing handicapped. The applicability of the European experience to North America is discussed.
Cross-spectral method of measuring acoustical intensity—correcting phase mismatch error by calibrating two microphone systems
Authors: Krishnappa G.
Published: October 2005

The accuracy of measuring acoustic intensity using two closely spaced microphones by correcting the phase mismatch error by measuring the transfer function between the two microphone systems is examined. The two measuring microphone instrumentation systems were calibrated by flush mounting the two microphones in a rigid circular plate attached to the end of a long length of circular pipe. A random noise source was mounted at the other end of the piping system. The two microphones were exposed to the same noise (phase and pressure levels) over a wide range of frequencies. The accuracy of the measurement method was verified by creating a sound field in an anechoic room by a loudspeaker and generating plane-wave propagation inside along length of pipe with an anechoic termination. The measurement accuracies were very satisfactory. This method has the advantage of eliminating the recording and processing of two sets of data required in circuit switching technique.
Carrier-operated microphone preamplifier with self-testing capability
Authors: Corliss Edith L. R. , Penzes William B.
Published: October 2005

In carrier-operated preamplifiers, a condenser microphone can be placed in series with an inductor in one arm of a modified Van Zelst bridge circuit [M.D. Burkhard et al., J. Acoust. Soc. Am. 32, 501–504 (1960)]. The microphone capacitance and the inductor are resonant at the carrier frequency. Consequently, the impedance of this arm is relatively low, and the signal-to-noise ratio can exceed that of a conventional high-impedance preamplifier circuit by an order of magnitude or more. Sound-induced motion of the diaphragm modulates the carrier frequency; demodulation and amplification produce the output signal. Advances in microelectronic components since 1960 include the availability of temperature-stable integrated circuits, small crystal-controlled oscillators, and temperature-compensated voltage references. These components were used to construct a carder preamplifier of small size suitable for use with “half-inch” microphones. Since the bridge circuit balance is dependent upon the electrical impedance of the microphone, changes in this impedance associated with changes in microphone sensitivity can be detected by use of an audio-frequency insert voltage. This insert technique provides a simple and convenient in situ check of the microphone and preamplifier. Tests for preamplifier battery supply and polarization voltage are also provided.
Transient response optimization of piezoelectric disk transducers by time domain techniques
Authors: Wolf H. A. , Lawther J. M.
Published: October 2005

The goals of this research have been to find and demonstrate design procedures for reducing the mechanical ringing of piezoelectric disk transducers under impulsive electrical excitation. The primary criterion of the optimization procedure is the minimization of face velocity ring-down peaks under the constraint of limiting loss from the peak velocity. Improvements to the transient response have been sought through the determination of appropriate matching networks at the two mechanical ports and at the electrical port. The optimization is accomplished by performing a gradient search over a parameter space defining the port matching configurations. The transducer and front-side mechanical matching sections are modeled with distributed parameters. Back-side loading is restricted to being resistive. Conventional inductance-tuned matching at the electrical port is demonstrated to be detrimental in reducing transient ringing. The findings indicate a natural division of the optimization process. Lightly backed and heavily backed transducers define the categories, each with an appropriate set of design criteria. Within each category, these new time domain optimization procedures result in improved transient performance over previously reported techniques based on frequency domain analysis. Experimental demonstrations are provided to verify the theoretical design improvements.
Advances in fiber interferometer hydrophones
Authors: Cole J. H. , Bucaro J. A.
Published: October 2005

Progress on the development of fiber interferometer hydrophones is presented. Baseline low-frequency noise has been systematically reduced over the past year. A dramatic improvement in minimum detectable pressure of fiber hydrophones at frequencies between 200 Hz and 1 kHz was recently achieved by the incorporation of state of the art optical components. The potential for increased performance of fiber interferometers is discussed.
Surface intensity patterns for a baffled plate
Authors: Brito J. Daniel
Published: October 2005

The spatial characteristics of the acoustic power flow at the surface of a baffled simply supported rectangular plate vibrating in flexural motion are studied to obtain an insight on the process of energy exchange between the plate and the acoustic medium. An expression for the local radiation efficiency as a function of space and frequency is presented and used to compute sound intensity patterns at the surface of the vibration plate, under different types of excitation of the plate-bending motion. The space average of the local radiation efficiency is compared with published values and with measurements by the reverberant room method. Frequency averages (13 octave band) of this local radiation efficiency at points on the plate are compared with measurements by the accelerometer-microphone method. Satisfactory agreements are obtained in all these comparisons. [Work performed at M.I.T.]