bluuebunny/crossref_metadata_2025 huggingface dataset:
Motor Vehicle Noise Bibliography
Authors: Muster Douglas
Published: October 2005

The manner in which the bibliography can be used is described. Commentaries are made on some of the most important recent publications.
A Linear System Approach to Room Acoustics
Authors: Martin Norman C. , Cook Bill D.
Published: October 2005

Taking the variables that effect the propagation of sound in a room, such as properties of the room confines, objects in the room, air absorption, etc., and assuming they are linear operators, we can formulate a linear system approach to room acoustics. Given the impulse response of a linear system, it is possible to find by analysis all the properties of the system, whether in the time domain or frequency domain. In relation to any two fixed points in a room, one for source input and the other for received signal pickup, by use of the principles of correlation, a method is available to derive the impulse response of the room. (This is one of several methods, but it is straightforward and successful in practical applications.) It follows that by experimentally determining the impulse response function of the system considered one can obtain in situ values of transmission and reflection coefficients, energy decay rates, and parameters required for prediction of sound levels from multiple coherent sound sources. Use is made of the correlation function a second time to generate standard acoustic quantities from the available impulse response function. [Supported in part by two grants from NASA.]
Computer-Assisted Measurement System for X-ray Films of the Vocal Tract
Authors: Mermelstein P. , MacLean D. J.
Published: October 2005

Measurements on sagittal x rays of the vocal tract may be made directly in terms of the variables of an articulatory model by superimposing a computer-generated vocal-tract outline onto the x-ray image. Previous methods require an operator to trace a pen or pointer coupled to a recording device along the outlines of the projected image. The new system uses two video signals, one derived from a television camera scanning the projected x-ray image, the second from data in a computer display buffer. The computer display is modified through adjustment of control potentiometers assigned to the model variables. Convergence to a match between the two images is found to be substantially quicker and easier task than manually tracing the image outline.
Examples of Parameterless Intensity Contours
Authors: Wood D. H. , Lesick Andrew A.
Published: October 2005

Intensity contours for several unbounded inhomogeneous media are found and graphed. Both layered and non-layered examples are included. Intensity contours are taken from parameterless examples of ray acoustics. That is, they are found without using rays, ray equations, or ray parameters. These examples are natural test cases for numerical procedures that also produce intensity contours. Examples of intensity contours generated by parameterless and numerical methods are compared.
Sound Pressure in Water from Source in Air and Vice Versa
Authors: Young Robert W.
Published: October 2005

Sound pressure level Lp at a depth d, in water, due to a point source in air at a distance h above the water surface, may be calculated from Lp = [Ls −7 + 20 log (cosθ)] −20 log(r/rs), where Ls, the source level, is the SPL in air at distance ra from the source; r is the straight-line distance to the receiving hydrophone from a virtual sound source situated under the actual source at height h′ = (c1/c2) × h above the surface; c1 and c2 are the respective speeds of sound in air and water; θ is the angle between the vertical and the line of length r. Comparisons with various published results obtained by more sophisticated ray-theory show agreement within 1 dB, except at shallow depths and far sidewise from the sound source; agreement within 2 dB is found for new experimental data here presented for sound bursts of frequency 500, 1000, and 2000 Hz, and h = 3.5 m. For sound originating in water at depth d below the surface, the SPL received in air is to be calculated from Lp = Ls −52 + 40 log(cosθ) −20 log(r/rs), where Ls is the source level, at rs;, in the water. Experimental data obtained with a sound source in the water at depth d = 5.6 m, and frequency 500, 1000, or 2000 Hz, are in agreement with this equation, mostly within 2 dB, for receiving positions in air 1 or 2 m above the water and offsets as great as 3 m.
Simulation of a Nonlinear Model of the Basilar Membrane on a Digital Computer
Authors: Hall J. L.
Published: October 2005

The generation and propagation of distortion products in a nonlinear model of the basilar membrane was studied. The basilar membrane was modeled as a 175-section transmission line, with hydromechanical coupling between sections. A version of this transmission line developed by Schroeder provides good agreement with Mössbauer effect and capacitive probe measurements of motion of the basilar membrane. The model was simulated on a Honeywell DDP-516 computer as a sampled-data system represented in terms of the bilinear z transform. Nonlinearities were introduced by making the compliance of the basilar membrane depend on its displacement. Both odd- and even-order distortion products have been investigated. Distortion products f2 − f1 and 2f1 − f2 (f2 > f1) are generated predominantly at the f2 place and propagate to their own characteristic place, and so can be equated to tones of frequency f2 − f1 and 2f1 − f2 applied at the input. This is not the case for distortion product 2f2 − f1.
A Thin-Film Intracochlear Multimicroelectrode
Authors: Sonn Martin
Published: October 2005

A flexible, intracochlear multimicroelectrode array is being developed for differential electrical stimulation of the cochlear nerve in human sensory deafness [M. Sonn, Proc. 25th Annual Conf. Eng. Med. Biol. 14, 159 (1972)]. The conductor elements, 0.3 μm thick, are formed on both sides of a thin-film plastic substrate using vacuum deposition and photolithographic etching techniques. In the present configuration, the array consists of 33 platinum conductors, 12.7 μm wide, each terminating at an electrode surface, 250 μm wide. The electrodes are spaced on 700 μm centers. Substrates investigated include Mylar, Parylene-C, and FEP and TFE Teflon films, 50 to 130 μm thick. Of these, Mylar was found best for electrode fabrication. Insulation of the array is accomplished by dip coating in Silastic. The electrode tips are exposed by mechanical scribing techniques. Short-term body tolerance studies in guinea pigs show good compatibility with the electrode materials. Bipolar sinusoidal stimulation of the electrodes in normal saline shows a decrease in complex impedance proportional to the −0.99 power of the frequency: 23.8 MΩ at 100 Hz to 250 kΩ at 10 kHz. Stimulation studies in vitro and in vivo (scalae tympani of cats) are planned to determine behavioral responses to electrical stimuli and long-term tissue reaction and electrolytic dissolution effects. [This work was supported in part by Raytheon Company.]
Near-Field Environments of VTOL Jets
Authors: Sutherland L. C.
Published: October 2005

For jet-powered VTOL aircraft, the principal sources of nearfield noise are the direct and ground-reflected noise of the jet exhaust, the aerodynamic noise from wall jet formed by the deflected exhaust flow and the noise of the impinging jet. These principal sources are considered and several of their basic characteristics for VTOL jet noise are established. Emphasis is placed on the change in acoustic power and near-field levels due to their combined effect. A prediction method for near-field noise of VTOL jets is then outlined in the form of additive corrections to apply to near-field levels for the undeflected jet. These corrections have a maximum value of about 15–20 dB in the range of typical resonance frequencies for flight vehicle skin panels. However, these additive corrections vary substantially with frequency and elevation of the vertically directed nozzle. The approximate trend in these variations is illustrated based on the results of model studies. [This work was supported by the Air Force Flight Dynamics Laboratory, Wright-Patterson Air Force Base, Ohio.]
Ray Propagation in Slowly Time Varying Deep Ocean Channels
Authors: Weinberg I. N. L. , Flanagan R. P. , Clark J. G.
Published: October 2005

Ray acoustics in deep ocean channels is being studied with the specific objective of describing the influence of low-frequency internal waves and surface tides upon multipath propagation. The work is a joint study in which the ray model is coordinated with a fluid dynamical investigation of the effect of internal tides upon deep ocean sound speed stratification. The geometry of the propagation channel consists of parallel boundaries and a composite sound speed profile with straight line segments in the main thermocline and deep water regions, and two hyperbolic cosines in the vicinity of the SOFAR axis with the slopes continuous at all junctions. For arbitrary source and receiver locations, the initial angles of all the ray arrivals were determined. Using closed form expressions for each segment, travel time and spreading loss were calculated from which amplitude and phase can be found. Complete descriptions of the propagation multipaths are given for selected examples which combine the several types of rays encountered in deep ocean transmission. In a subsequent presentation (Part II), the time variations in these multipaths due to tidal fluctuations in the sound structure are discussed.
Binaural Interaction with Stimuli that Produce Periodicity Pitch
Authors: Hafter E. R. , Ricard G. L.
Published: October 2005

Periodicity pitch was produced by 100% modulation of bandlimited white noise. The periodicity waveform was rectangular with a 500-Hz repetition rate and a 10% duty cycle. Two gates were used to present the modulated noises separately to the two ears. The gates carried the same noise, but the modulation waveforms were delayed by Δt μsec so that the noise came on first in the leading ear and went off last in the lagging ear. Perception of these stimuli and the consequent detection of Δt was shown to be dependent on the frequencies of the carrier: for low-frequency noise, the lateralized percept was on the side of the leading ear, while for the high-frequency noise it was on the side of the lagging ear. A model that describes these results interprets the lateralization obtained with the low-frequency carrier as responses to the onset of the dichotic bursts and the lateralizations obtained with the high frequency carrier as responses to the offsets of the bursts.
Detection of Interaural Time Differences in Short-Duration Low-Frequency Tones
Authors: Ricard G. L. , Hafter E. R.
Published: October 2005

The detectability of interaural time differences (Δt) was investigated as a function of stimulus duration, level, and frequency. Temporally dichotic tone bursts of 250, 500, and 1000 Hz were presented in a two-interval forced choice, in such a way that the signal to one ear led by Δt μsec during either the first or second interval. The tone bursts were 10, 25, 50, 100, and 205 msec in duration and were gated with a rise-decay time of 2.5 msec. The levels used were 50 and 70 dB SPL. Threshold values of Δt were maximal for the shortest durations, then fell rapidly to asymptote in the region from 50 to 100 msec. In addition, thresholds decreased at higher frequencies. Finally, all conditions showed lower thresholds for 70 dB than for 50 dB. The data are fit by a model that treats increased duration as an increase in the number of samples of the interaural difference and describes the improvements found with higher frequencies and levels as a result of the steeper slopes of the displacement waveforms.
Binaural Processing in the Cat. I. Lateralization
Authors: Wakeford O. S. , Robinson D. E.
Published: October 2005

The ability of the cat to “lateralize” tonal signals having interaural intensive or interaural temporal disparities was measured. Interaural intensive differences were studied at 0.5, 1.0, and 3.0 kHz. Interaural temporal differences were studied at 0.5, 1.0, 2.0, and 3.0 kHz. Miniature audio transducers were employed to present the stimuli to the animals. The transducers were held in a fixed spatial relation to the auditory canal by means of “pinna inserts” and leather helmets. An avoidance response in a shuttle box was used as the dependent variable. The animals' task involved the detection of a right-left reversal in a gated sequence of tone bursts. The cat appears to be about as sensitive as the human to both interaural intensive and temporal disparities at each of the frequencies studied. [This research was conducted at Indiana University, Bloomington, Indiana.]
Certain Digital Quadrature Techniques for Bandlimited Signals
Authors: Grace O. D.
Published: October 2005

Practical methods of signal processing of bandpass signals by digital quadrature methods are discussed. These methods assume a sufficiently dense uniform sampling of a bandpass signal and include extractions of quadrature samplings from uniform samplings; polynomial interpolations, in which the sampling frequencies fs>πW ensure exact interpolation; and error corrections for interpolations over a finite data base. Also included are applications to the problems of measuring the instantaneous envelope, phase, and frequency of bandpass signals.
Noise Reduction by Barriers
Authors: Kurze U. J.
Published: October 2005

A literature review is prepared to summarize the present state of knowledge concerning the field performance of barriers, with particular reference to screen-type barriers on finite impedance ground, to barriers of finite thickness, to right-angle wedges, to multiple barriers, and to effects of wind. The attention is focused on practicabilities and limitations of prediction schemes applied for the design of barriers, which shall reduce the noise ontdoors from vehicles on the ground and from stationary installations.
Technique for Measuring Ultrasonic Power
Authors: Ziedonis J. G.
Published: October 2005

It is vitally important to know accurately the ultrasonic energy levels of electronic equipment that generates and sends ultrasonic energy into the human body. Therefore, a radiation force measuring technique was developed to measure the ultrasonic energy generated by such equipment. Ultrasonic energy levels of less than 1 mW/cm2 have been measured, with good repeatability. The equipment used is a Mettler Balance, model H-20-T, with a readable sensitivity of 0.01 mg and a target that detects the incident radiation force. The target is attached to the balance weighing pan and suspended in water under the balance by a nylon line. The balance has a built-in tare, used to counteract the ultrasonic energy force that illuminates the target. In addition the tare is adjusted to counteract the surface tension that normally occurs at the nylon support line, which would interfere with the accuracy of power measurements. The target consists of an air-backed reflector that has a half angle of 45°. This angle and the air space behind the thin metal surface makes the target a nearly perfect reflector. To make certain that no ultrasonic energy is reflected from the walls of the water tank, the ends of the tank are tilted about 20°, and all the inside surfaces are lined with ultrasonic energy absorbing material. This equipment has been in use now for over a year. Ultrasonic energy power measurements have been made on many different sizes, configurations, and frequencies of ultrasonic transducers. Details of this technique of measuring ultrasonic power will be reviewed in the paper.
High-Performance Magnetostrictive Transducers
Authors: Edson A. P. , Huston E. L.
Published: October 2005

This paper is directed to the use of magnetostrictive materials for the generation of high-intensity mechanical vibration, sound, and ultrasound. It will present a mathematical analysis of a novel method of electromagnetic polarization and excitation that affords previously unattainable combinations of peak-to-peak magnetostrictive strain energy, electromechanical efficiency, and linearity. The analysis is based on a nonlinear model valid for isotropic, square-law magnetostrictive materials. To achieve these results, electromagnetic excitation is applied at a large angle relative to the axes of static polarization and mechanical output. Because this is usually most conveniently achieved by application of magnetic vectors at right angles to one another, the method has been termed “orthogonal excitation.” A specific system for orthogonal excitation, which permits electromagnetic self-polarization, will also be discussed.
Attenuation of a Resonant Dissipative Silencer in a Rigid Duct
Authors: Trella Thomas J. , Kasper Peter K.
Published: October 2005

Sound attenuation characteristics of a resonant-type dissipative silencer consisting of a reactive chamber with a porous facing have been considered. Such a silencer provides a high degree of attenuation within a narrow frequency range. Predicted attenuation values are compared with experiment for plane waves propagating in a rigid duct containing the dissipative silencer. The sound field is described by one-dimensional acoustical expressions taking into account the effect of boundary conditions and the presence of the silencer. The theoretical model incorporates the acoustical properties of porous materials and inertance of the sound field in the duct adjacent to the silencer. Good agreement was achieved between theoretical predictions and actual measurements. Results presented indicate the dependence of the attenuation spectrum upon flow resistivity and thickness of the porous material.
Noise and Vibration Reduction in Piping Systems by Flexible Couplings
Authors: White P. H. , Rentz P. E.
Published: October 2005

Unwanted noise and vibration in piping systems, generated by pumps, valves, or orifices can be attenuated by flexible couplings. The efficiency of the resulting noise reduction is governed by the physical characteristics of the devices and the distribution of energy between the pipe wall and the contained fluid. A good attenuator must reduce both fluid-borne and structure-borne noise. Experiments confirm the analytical prediction of energy distribution for acoustic and mechanical excitation of the system. Further experiments on various 4-in.-diam flexible couplings demonstrate their relative noise reduction characteristics for fluid- and structure-borne noise. A two-element right-angle configuration is shown to be even more than twice as efficient as one isolator, particularly at low frequencies.
Measurement of Acoustic Impedance of Several Artificial Ears
Authors: Record H. D. , Hixson E. L.
Published: October 2005

The driving point acoustic impedance of five artificial ears was measured over the frequency range 100–7000 Hz. An acoustic impedance measuring device was constructed, and consisted of a small pistonphone, equipped with an accelerometer within the piston and a 18-in. insert microphone. Operational amplifier integration and summing, together with an XY recorder, allowed the continuous plotting of measured acoustic impedance as the frequency range was swept. Since acceleration and pressure were not measured at precisely the same point in the system, a computer program was used to perform the required phase correction and thus obtain true driving point impedance values. The impedance measuring device and phase correction procedure are described, and the results of the measurements are presented. Artificial ears included are the NBS-9A coupler, the ANSI type 1 coupler, the B&K type 4153 artificial ear, a TRACOR experimental coupler, and an artificial ear constructed for this study. Measured values of acoustic impedance are compared with design values.
Influences of Phonetic Sequences and Stress on Fundamental Frequency Contours of Isolated Words
Authors: Lea Wayne A.
Published: October 2005

At vowel onset following unvoiced consonants in /həCVC/ utterances spoken by two talkers, F0 began high (30% higher than in /ə/), and fell about 7% in the first 5 csec. At closure of voiced oral obstruents, F0 suddenly dipped about 10%, remained flat, suddenly rose about 25% at opening of closure, and, after vowel onset, gradually rose (an average of 8% in the first 10 csec). The high/low feature of the vowel and the manner and place of prevocalic consonant articulation had progressively less effect on vowel F0 values. The final consonant had no apparent effect on F0 contours in the vowel. As previous synthesis work has suggested, the fall or rise of F0 in the initial portion of a vowel appears to be a cue to the state of voicing of previous consonants. Initial and peak F0 values in the vowel also can indicate state of consonant voicing. However, F0 contours in bisyllabic words with contrasting stress patterns and similar phonemic sequences (e.g., permit, permit) showed that (1) an initially falling F0 in a vowel may indicate either previous unvoiced consonant or an unstressed vowel, and (2) a rising F0 contour may indicate either a word-initial vowel, a preceding voiced consonant, or a stressed vowel.
A Computerized Audiometric System for the Fail-Detect Monitoring and Self-Calibration of Frequency and Hearing Level
Authors: Wood T. J.
Published: October 2005

Past research has indicated the need of frequent monitoring and calibration of audiometric stimuli. This study investigated the applicability of an automatic monitor and self-calibration system for frequency and hearing level employing relevant computer peripheral equipment and a mini-digital computer. Unacceptable drifts in frequency and hearing level were intentionally introduced into the system by respectively turning the frequency selector dial of a function generator and an attenuator. After monitoring and, if indicated, computerized calibration, the signals were subsequently sampled via traditional calibration equipment to determine the frequency and hearing level parameters of the computer-revised signals. The obtained data were analyzed in terms of means, standard deviations, average deviations, and maximum errors encountered at each of six audiometric frequencies (250 Hz–8 kHz). The results of this study indicate the feasibility of providing frequent stimulus monitoring and self-calibration within a system of computerized audiometrics. [This research was supported, in part, by the University Research Council of the University of North Carolina.]
Acoustical Signature of Some Hand Guns Commonly Employed in Law Enforcement
Authors: Kobal M. T. , Weissler P. G.
Published: October 2005

Small condenser microphones and a storage oscilloscope were used to record the N-wave signatures from a 9-mm Ruger, 0.357 magnum, 0.41 magnum, 0.22 long rifle, 0.44 magnum, 12-gauge shotgun, and 0.22 rifle. Measurements were made at the ear of the person shooting and at the approximate position of a neighbor at a firing range. Data on peak SPL and durations (A and B durations) are given, as well as data obtained at a practice firing range. The results are discussed from the point of view of using ear defenders to protect against temporary and permanent threshold shift incurred during practice. [Research supported by the National Institute of Law Enforcement and Criminal Justice.]
Exact Solution for Transmission Matrix of Liquid-Filled Pipe Using Sylvester's Theorem
Authors: Samsury D. R.
Published: October 2005

The differential equations describing the vibrational behavior of a liquid-filled curved pipe are presented. The corresponding eigenvalue problem is formulated in terms of the coefficient matrix of these equations in the usual (λI − B) form. With the aid of a special computer program, general polynominal expressions for the elements of the adjoint of (λI − B) and its characteristic equation are obtained in terms of λ and elements of (B). A simple matrix operation is used to validate their form. Solution of the characteristic equation yields the eigenvalues and thus values for the adjoint matrix. Using this information and Sylvester's theorem, the desired transmission matrix (U) is obtained. (U) reflects the effects of shear deformation, rotary inertia, damping, and cross-sectional deformation. Difficulty in obtaining the 14 distinct eigenvalues is discussed as is the case of repeated eigenvalues. The final transmission matrix is compared to one obtained by a demonstrably accurate numerical approximation method.
Prediction and Measurement of the Proportionality Constant in Statistical Energy Analysis of Structures
Authors: Lotz Robert , Crandall Stephen H.
Published: October 2005

The fundamental equation of statistical energy analysis (SEA) states that the average power flow between two coupled vibrating systems is proportional to the difference in their average modal energies. Under certain circumstances, one can estimate the proportionality constant by modifying system boundary conditions on the separated systems and calculating or measuring changes in the systems. Newland's estimate, based upon blocking part of the system, is reexamined and limitations are discussed. Three alternative methods which circumvent blocking are presented. They are based, respectively, upon (1) natural frequency shift due to addition of mass; (2) mechanical input impedance; and (3) mean square velocity response at the excitation point due to random excitation. The new methods were applied to predict power flow in experiments on coupled beams and on coupled plates. One or both parts of the coupled structures were then excited by external random sources, and power flow through the coupling was measured directly as a product of force with velocity. The fundamental SEA relation was supported by the measurements, which included the null power point where the difference in average modal energies was zero. Measured and predicted proportionality constants are compared. [This work was supported in part by the National Aeronautics and Space Administration.]
Measured Effects of Ice Roughness on under-Ice Transmission Loss
Authors: Diachok O. I. , Kozo T. L.
Published: October 2005

Coincident measurements of under-ice transmission loss over a frequency range of 100–1000 Hz and top ice roughness were made from aircraft. The acoustic measurements were made with calibrated sonobuoys and explosive charges, while top ice roughness measurements were made using a laser profiler along several 100-km tracks. The resulting ice roughness data is expressed in terms of ridge density. As expected, low-frequency transmission loss increases with top ice ridge density. According to a preliminary analysis of top and bottom ice roughness data, top ice ridge density is a quantitative indicator of bottomside ridge density and rms roughness. The data are compared with theoretical predictions and previous measurements. Some possible acoustic scattering mechanisms at the water-ice interface are suggested.
Acoustic Assessment of North Pacific Salmon Stocks
Authors: Acker W. C.
Published: October 2005

Acoustic sampling of various fish stocks and the acoustic characteristics of fish targets are being investigated as part of the Marine Acoustics Program at the University of Washington. An important outgrowth of this research is the development of a free-floating acoustic system which is being used to help index the North Pacific salmon population. This is an uplooking system which operates at 250 kHz. Average target size of the migrating salmon is about − 30 dB within the aspect angles encountered in the sample volume. Acoustic source level and TVG receiver sensitivity were adjusted for that average size, but a fairly wide range of target-size fluctuation can be accommodated (±10–15 dB). Studies of relative abundance indicate that the population density in particular areas is related to the spawning migration to Bristol Bay, Alaska, the following year thus providing an index of population abundance [D. E. Rogers, Fish Rec. Inst. Circ. ♯70-7 (1970)]. A second acoustic system is now being developed for use in Bristol Bay to generate population data upon which to base the day to day management of the fishery so that catch and escapement are optimized.
Calibration Accuracy for Small Standard Hydrophones
Authors: Blue J. E.
Published: October 2005

When a standardizing laboratory issues a certificate for a standard, it attributes to that standard a numerical value together with a statement about the uncertainty of this value. In the measurement of the sensitivity of an unknown hydrophone performed once, most activities will claim an accuracy of ±1 dB. Usually no confidence limits are specified, and the accuracy is an educated guess based on experience. This paper discusses the careful “free-field” reciprocity calibration of two small standard piezoelectric hydrophones in a stable environment and the use of these hydrophones in evaluating the calibration performance of six of the established calibration facilities at the Underwater Sound Reference Division of the Naval Research Laboratory. The results of these measurements show that, for the most part, accuracy of the facilities is well within the ±1 dB commonly quoted and is probably within ±0.3 dB with 95% certainty at some of the facilities when calibrating small standard piezoelectric hydrophones.
Spatial and Temporal Distribution of Sound Pressure Levels in Data Processing Installations
Authors: Lang W. W. , Maling G. C. , Wise R. E.
Published: October 2005

The sound field in a data processing installation depends upon the locations of the sound sources, the sound power radiated by the sources, the acoustical properties of the room (including its total absorption area, volume, and shape), and the background noise levels in the room due to external sources. Spatial and temporal variations in the sound field are observed in typical installations. The relative importance of the individual factors affecting the sound field is assessed. The results of this study show that a scale factor may be used to predict the SPLs in an installation from SPL data obtained on individual machines in a semi-anechoic room. Hence, semi-anechoic room data are useful for predicting installation noise levels and for guiding the design of a particular data processing environment, as well as serving as a measure of source emission during the design and development of a new data processing machine.
Noise Exposure Meter Performance—Results of an Evaluation Program
Authors: Leasure W. A. , Fisher Ronald L.
Published: October 2005

As a result of the promulgation of occupational noise exposure regulations by the Federal government, there are a number of noise exposure meters on the market today that provide a measure of noise exposure integrated (with appropriate weighting) over a time interval. The National Bureau of Standards (under the sponsorship of the Environmental Protection Agency) has completed total system and component evaluations on a number of different commercial models of noise exposure meters. Overall system performance tests were used to evaluate the dynamic response of the system and the nature and accuracy of the time integration for increasing and decreasing, as well as stationary, signals. The following tests were conducted to evaluate subsystem performance: microphone response to sounds of random incidence, A-weighting network response, detector response and averaging time, and accuracy of the readout system. The rationale of the test procedure utilized, details of the measurement techniques, and results obtained are discussed.
The Control of Complex Auditory Cortex Units in the Unanesthetized Monkey
Authors: Miller J. , Beaton R. , O'Connor T.
Published: October 2005

Cortical cells exhibiting “complex” response patterns to acoustic stimuli have been studied in the unanesthetlzed and behaving nonhomart primate. The response of these cells consists of more than one temporally restricted component. For example, cells have been observed with on and off components that are either excitatory or suppressive, or some combination of these. In one sample of approximately 100 cells, 30% exhibited a complex response pattern. In at least 20% of these, the individual components of the response pattern have been found to vary independently with changes in frequency of tonal stimulation and/or intensity of the sound stimulu s. Representative examples included cells with an on and off component in which each component had a different best frequency or cells in which the relationship of frequency of firing to intensity of stimulation differed for each response component. Such observations lead to questions concerning the coding of signal information in terms of temporal characteristics of response patterns, and the manner in which response characteristics of higher auditory cells may be structured and controlled. From our observations, it is suggested that independent cellular inputs contributed at points along the central auditory pathway control the firing characteristies of some cortical cells. Analogies may be drawn to the structuring of receptive field characteristics of cells in the visual system. [Research supported by NIH Grants.]
Ultrasonic Velocity Measurements in Liquids at High Temperatares and Pressures
Authors: Jarzynski Jacek
Published: October 2005

An apparatus is described for speed of sound measurements in molten metals and fused salts as a function of temperature and pressure. Problems encountered in extending the temperature and pressure range are discussed. The ultrasonic velocity data are used to determine the equation of state of the liquid investigated [L. Davis and R. Gordon, J. Chem. Phys. 46, 2650 (1967)]. Results are presented for the temperature range up to 500°C and pressure range up to 1000 atm. However, using the apparatus described, such measurements may be obtained over a considerably larger pressure and temperature range than covered in this investigation.
Propagation of Sound in Critical Binary Liquid Mixtures near the Critical Point
Authors: Hunter J. , Mole L. , Dill J. , Vimilvanich S.
Published: October 2005

It is well known that very large attenuation of sound is produced in critical binary liquid mixtures as the critical temperature is approached, but there is disagreement whether this large attenuation is due to scattering or to true absorption. We have scanned the radiation emanating from a scattering cell containing a binary liquid mixture at several closely spaced temperatures near the critical temperature. Whereas there is a very large drop in the strength of signal at zero bearing angle, there is no consequent rise at any other angle, as there is in the case of true scattering (e.g., as has been experimentally found in scattering from air bubbles.). We conclude that the attenuation measured by previous observers should be assigned primarily to true absorption, and that the effect due to scattering is negligible. [Work supported by the Office of Naval Research, Acoustics Branch.]
The Right Ear Advantage for Speech Processing
Authors: Herman Steve
Published: October 2005

Spoken digits, words, CV syllables, and Morse code are recognized and recalled better by the right ear than the left; nonverbal sounds, such as melodies, tones, sonar beeps, and toilet flushes are processed better by the left ear than the right. In general, however, ear differences have been obtained with dichotic, but not monaural stimulation. To account for these findings, Kimura proposed that under dichotic stimulation the ipsilateral auditory connections are inhibited, thus giving the right ear “privileged access” to the language-dominant left hemisphere. Several findings involving monaural stimulation, verbal and nonverbal interference tasks, etc., are presented that indicate that Kimura's theory is inadequate. An alternate model based on interhemispheric transfer of information is proposed.
Perceptual Processing Time for Consonants and Vowels
Authors: Pisoni D. B.
Published: October 2005

Perceptual processing time for brief CV syllables and steady-state vowels was examined in a backward recognition making paradigm. Subjects were required to identify a 40-msec target sound selected from either a consonant set (/ba/, /da/, /ga/), or a vowel set (/i/, /I/, /ε/). The target sound was followed by a different sound drawn from the same set after a variable silent interstimulus interval. The second sound interrupted the perceptual processing of the target stimulus at short interstimulus intervals. Recognition performance improved with increases in the silent interstimulus interval. One experiment examined processing time for consonants and vowels under binaural presentation. A second experiment compared consonant and vowel recognition under both binaural and dichotic presentation. The results indicated that (1) consonants require more processing time for recognition than vowels, and (2) binaural and dichotic presentation conditions produce differential effects on consonant and vowel recognition. These findings have several implications. First, speech perception is not immediate, but is the result of several distinct operations that are distributed over time. Second, speech perception involves various memorial processes and mechanisms which recode and store information at different stages of perceptual analysis. [Research supported in part by grant to Haskins Laboratories from NICHD and a PHS Bio-Medical Sciences Grant to Indiana University.]
Categorical and Noncategorical Modes of Speech Perception along the Voice Onset Time Continuum
Authors: Lazarus Joan House , Pisoni D. B.
Published: October 2005

Synthetic stop consonants varying in voice onset time (VOT) are generally perceived in a categorical mode. Listeners can discriminate two sounds only to the extent that the stimuli have been categorized as different phonetic segments. In the present study, native speakers of English were required to first identify and then discriminate stimuli which varied in VOT from /ba/ to /pa/. One group of listeners took a randomized absolute identification test, whereas another group took a sequential identification test. In the latter condition, stimuli along the continuum were presented in consecutive order. Half of the subjects in each group then took either an ABX discrimination test or a 41AX test. In the 41AX test, two pairs of sounds were presented on each trial. One pair was always the same and one pair was always different. Subjects were required to judge which pair was the same, the first or second. Noncategorical perception of the voicing distinction was obtained only for the group of listeners who received both the sequential identification test and the 41AX discrimination procedure. These findings suggest separate auditory and phonetic levels of processing in speech discrimination.
Comparison of Various Methods for Computing the Axially Backscattered Field of a Prolate Spheroid
Authors: Pijanowski J. , New R.
Published: October 2005

It is difficult, if not impossible, to obtain error bounds on many solutions to high-frequency scattering problems. Consequently, comparisons between solutions can be very helpful in establishing domains of validity. The backscattered field from a rigid prolate spheroid, ensonified by a plane wave, is calculated using the Keller, Kirchhoff, Luneberg-Kline, and geometrical-optics methods. These results are compared to each other, and to the more exact wave-harmonic result. Finally, results from a finite element method, employing Schenck's CHIEF program, are compared. Limitations on the various methods are discussed.
Pitch Shift and Masking by Sinusoids and Narrow-Band Noise
Authors: Taylor M. M. , Smith S. M.
Published: October 2005

Direct masking of a sinusoid by a 10-Hz noise band defines an apparent filter with a 3-dB bandwidth of as little as 7 Hz at 500 Hz. This extreme sharpness is probably found because the center frequency of the filter shifts away from the noise frequency. We have found perceived pitch shifts of as much as 10 Hz for tones 30 dB above their masked threshold. With a sinusoidal musket, less masking is found for small frequency separations, presumably because beats between signal and musket are heard, whereas with the narrowband musket, they are masked by “beats” internal to the noise. When either a 10-Hz noise band or a sinusoid fixed at 470 Hz is used to mask a 500-Hz sinusoid, and a sinusoid at another frequency is used as a secondary masker, masking is enhanced by as much as 15 dB, presumably because of extra beats generated within the critical band filter. Preliminary results suggest that the filter is over 200 Hz wide at 500 Hz. Masking of beats by other beats could be a powerful tool in investigating the primary organization of the auditory system.
Durational Characteristics of Word-Initial Consonant Clusters in English
Authors: Klatt Dennis H.
Published: October 2005

A list of 224 English words beginning with prestressed consonant clusters or single consonants were recorded in the frame “Say … instead” by three talkers. Consonantal durations were measured from spectrographic analysis of the data. The results indicate that consonants in clusters are generally shorter than in a singleton environment, but that the amount of shortening is dependent on certain features of adjacent consonants. A system of durational adjustment rules is proposed in order to account for the statistically significant durational differences. If the consonantal duration in the singleton environment is considered as the standard duration, then rules (1) shorten two-element clusters by about 12%; (2) shorten three-element clusters by about 18%, (3) produce additional shortening in a consonant that is followed by a balistic closure; (4) produce additional shortening in a sequence of two voiceless consonants; (5) prevent labials from being shortened as much and shorten adjacent segments somewhat more to compensate; (6) lengthen a consonant if a preceding plosive causes aspiration to be present during a portion of the consonant; and (7) produces additional shortening in a sequence of two dentals. Implications for articulatory modeling, speech perception, and speech synthesis by rule are discussed. [Work supported in part by National Inst. of Health and by Office of Naval Research.]
An Interpretation of the “Frequency of Least Reflection” at the Rayleigh Angle for a Liquid-Solid Interface
Authors: Neubauer Werner G.
Published: October 2005

Ultrasonic receiver detection of a reflected beam at the Rayleigh angle has resulted in the interpretation of a minimum amplitude for a given material at some frequency called the frequency of least reflection. Recently it has been found that, in general, it is more meaningful to regard the reflection of a finite beam as energy redistribution rather than a reemergence of the beam in the same form as it had on incidence. At low megahertz frequencies, that redistribution ,nay be regarded as consisting of three distinct regions: a specular region, a Rayleigh wave radiation region, and a mutual interaction region of the specular and Rayleigh radiations. This model based on schlieren photographs is used to show that the “frequency of least reflection,” observed with a hydrophone, can be explained in terms of energy redistribution.
Critical Angle for Reflection from a Water-Quartz Interface
Authors: Henneke Edmund G. , Jones Gerald L. , Liu John Moyu , Green Robert E.
Published: October 2005

A new, general definition is given for the critical angle of reflection in anisotropic materials. While the critical angle for reflection at a liquid-isotropic-solid interface can be written in the form sinθc = vI/vR, we show here that, in general, for an anisotropic solid, the right-hand side of this expression must be modified by the factor cosφ/cosβ, where φ is the angle between the normal to the refracted wave in the solid and its energy flux vector and β is the angle between the energy flux vector and the component of the refracted wave normal on the interface. Numerical calculations have been made for this general definition for a water-quartz interface for planes of incidence about the z axis (the xy Diane being the interface). These calculations are compared with the value of the critical angle as determined by the unmodified definition. It is shown that this earlier definition can lead to large errors when one uses the experimental technique of measuring the critical angle to evaluate the elastic constants of the solid.
Further Studies on Cross Correlations between Fluid Dilatations and Flow Noise
Authors: Rackl R.
Published: October 2005

Following Ribner's dilatation model of turbulent flow, the fluctuating pressures in a jet are considered the sources of sound radiation. Cross correlation between the jet pressure and the noise in the farfield yields the distribution and character of the sound sources in the flow. From the correlation-function, the acoustic source strength,and by applying a Fourier transform, the frequency spectrum of the sound radiated per unit volume of turbulence are obtained. Errors in pressure measurement due to turbulent velocities interacting with the pressure sensor are discussed. It is shown that a cylindrical probe is inadequate for pressure measurements in the present case because of additional dipole noise generated by the turbulent flow impinging on the probe and thereby contaminating the cross correlation. Both the above difficulties are considerably reduced by a foil-type pressure sensor; its design is discussed in detail. The distribution of noise sources in a subsonic jet as they are radiating in a direction of 45°to the jet axis and the frequency spectra associated with these sources are presented.
Field Measurement of Noise Reduction between Spaces
Authors: Quindry T. L. , Flynn D. R.
Published: October 2005

The present ASTM procedure for field measurement of the noise reduction between spaces is time consuming and costly because it requires numerous measurements in order to compute the noise isolation class (NIC), particularly when separate measurements must be made at multiple microphone positions to obtain adequate spatial averaging. The purpose of the present investigation is to explore the relationships between NIC values based on 13-oct band data and more easily obtained ratings of isolation based on either octave band data or on A-weighted or C-weighted sound level data. A large number of curves of 13-oct band noise reduction versns frequency were calculated from data on transmission loss of partitions, assumed room geometry, assumed values for the source sound power spectrum, and assumed values for the sound absorption in the source and receive rooms. For each of these 13-oct band noise reduction curves, the following quantities were calculated and compared: NIC rating, Ia rating (13-oct band data), Ia rating (octave band data), the A-weighted sound level difference, and the difference between the C-weighted level in the source room and the A-weighted level in the receive room.
Response of a mechanical oscillator to a gravitational wave
Authors: Westervelt Peter J.
Published: October 2005

The conventional treatment [J. Weber, General Relativity and Gravitational Waves (Interscience, New York, 1961)] of an undamped mass quadrupole oscillator driven by a gravitational wave assumes the excitation force to be that exerted by the wave on the mass. The force exerted by the wave on the spring has heretofore been ignored. I have calculated this latter force Fs driving the spring and discovered that it is related to the force Fm driving the mass; thus, Fm = ω0−2 d2dt2 Fs, in which ω0 is the resonant circular frequency of the oscillator. The total driving force is the sum Fm + Fs. This total force is incapable of exciting the normal mode of the oscillator, thus supporting my earlier conjecture [P. J. Westervelt, Soviet Phys. JETP Letters 4, 225 (1966), Footnote 4] that passive detectors of gravitational waves cannot be realized in principle. Active detectors, i.e., generators of gravitational waves, can measure radiation from another source.