bluuebunny/crossref_metadata_2025 huggingface dataset:
Estimation of Exponential Power Spectra
Authors: Hinich Melvin J.
Published: September 2005

Many naturally occurring random processes, such as ambient sea noise, have the property that the logarithm of their power spectra is approximately a linear function of log frequency. It is difficult to estimate a power spectrum with a steep negative slope due to the leakage of low-frequency power into the higher-frequency bands by the digital filter of the estimator. This spectral estimation problem can be simplified by assuming a two-parameter model of the spectrum S (f). Let X (t) be a stationary Gaussian process with zero mean and lnS (f) = ln (σ2θ/2) −θ|f|, where θ and σ2 are unknown parameters. The total power of X (t) is σ2 and the mean frequency is θ−1. These parameters are estimated by simple functions of the number of zero crossings of X (t) and the number of fixed level crossings in a given finite record. The estimator of ln S (f) is ln (σ̂2θ̂/2) − θ̂f, where σ̂2 and θ̂ are the parameter estimates. For fixed σ2, the large sample variances of θ̂ and lnŜ are derived and computed for θ = 14, 12, 1, and 2. Monte Carlo methods are used to estimate the medium sample properties of θ̂ and σ̂2. The variance of lnŜ is of the order of T−1, whereas the variance of the standard digital estimator of lnS is of the order T−12, where T is the record length.
Sea Lion Echo Ranging
Authors: Shaver H. N. , Poulter T. C.
Published: September 2005

Recordings of a short series of sea lion pulses are analyzed. The approach used in the analysis is to infer echo-ranging capabilities based upon the full utilization of the signal properties. The analysis has led to the hypothesis that, in addition to echo-ranging pulses and possible communication signals, the sea lions—at least in some circumstances—generate and transmit signals that are used in the detection of target returns of echolocation pulses. In this framework, the actual echolocation pulse is the precursor pulse, and the main pulse is generated as part of the detection procedure. The resulting cross-correlation detection approximates the optimum detection technique. Finally, it is concluded that, for the signals considered, range may be measured to within approximately ±4 cm and that, for range rates of interest—say, up to 5 m/sec—the signals provide essentially no range-rate discrimination.
Detection and Localization: An Extension of the Theory of Signal Detectability
Authors: Hershman Ramon L. , Lichtenstein M.
Published: September 2005

The theory of signal detectability is extended to detection and localization (DAL). We treat the following problem: on each trial there are k noisy observation intervals, and at most one of these contains a known signal; an observer makes one of k+1 responses, indicating “NO SIGNAL IS PRESENT” or “THE SIGNAL IS IN INTERVALj” (1⩽i⩽k). The observer is scored “correct” on a noise only trial if he reports “NO SIGNAL” he is scored “correct” on a signal-plus-noise trial if he correctly localizes the observation interval containing the signal. We derive the decision rules for maximizing percent correct, P(C); these are based on the likelihood ratio of the observation in each interval. Our analysis shows that the ideal DAL receiver consists of the sequential application of YES-NO (YN) and forced-choice (FC) decision-makers. Under the assumption that monotonic transforms of the likelihood ratio are normally distributed, we obtain numerical results for P(C) as a function of k and the statistical separation of the noise and signal-plus-noise. Ideal performance on the DAL and FC problems is compared, and some multisignal cases are briefly considered.
Temporal Summation for Critical Bandwidth Signals
Authors: Northern Jerry L.
Published: September 2005

Temporal summation patterns were established for noise signals with critical-bandwidth frequency spectrums centered at 1000 and 4000 cps. Critical-bandwidth levels were calculated from group-mean masked thresholds and converted to critical-bandwidth noise signals. These measures were conducted for nine stimulus durations ranging from 10 to 1000 msec in ten normal-hearing, and ten cochlear-impaired subjects. Temporal summation functions for critical-bandwidth levels and critical-bandwidth signal thresholds were in good agreement except at 4000 cps in the cochlear-impaired group. These subjects showed no change in absolute threshold for the critical-bandwidth noise signals as a function of increasing stimulus duration time.
Head Movements During Sound Localization
Authors: Thurlow Willard R. , Mangels John W. , Runge Philip S.
Published: September 2005

Subjects were photographed with a moving-picture camera as they attempted to localize each of 10 sound sources in an anechoic room. High- and low-bandpass thermal noise stimuli of 5-sec duration were used. Changes in angular position of the head (and thus the ears) were measured from the film. Rotation movements of the head about a vertical axis (turning, left or right) were most commonly found—alone, in combination with tipping movement (nose up or down), or in combination with both tipping and pivot movements. (A “pivot” movement involves an increase in vertical height of one ear and a decrease in vertical height of the other.) A number of subjects also showed reversals in movement. The reversals were most prominent in the case of rotation movements. Quantitative summaries of observed movements are given.
Multiple Reflections in a Free Piezoelectric Plate
Authors: Stuetzer O. M.
Published: September 2005

This paper treats the development of thickness-dilational acoustic transients in mechanically free piezoelectric plates. In particular, the effects of external electrical loading circuitry are studied. These effects are most pronounced under short-circuit conditions. In a short-circuited voltage-step excited plate, stress and current responses consist initially of alternating exponential pulses. These, in an unexpected manner, decay to a sine wave accompanied by a sequence of sharp spikes. The sinusoidal and the spike system are characterized by different periods. A small signal theory for lossless materials is presented and supported by experiments with plates made of quartz and lead titanate-zirconate. The arrangement is useful for dynamic measurement of piezoelectric constants.
Activation of Auditory Cortex by Clicks after Bilateral Lesions of the Brachium of the Inferior Colliculus
Authors: Osman Eli , Galambos Robert
Published: September 2005

This report confirms the observation that subsequent to bilateral destruction of the brachium of the inferior colliculus, short-latency click-evoked responses at primary auditory cortex exist which can be blocked by a surgical dose of barbiturate anesthesia.
Comments on “Technique for Correcting Helium Speech Distortion” [W. R. Stover, J. Acoust. Soc. Am. 41, 70–74 (1967)]
Authors: Golden R. M.
Published: September 2005

The time-adjustment technique for correcting the peculiar sound of helium speech [W. R. Stover, J. Acoust. Soc. Am. 41, 70–74 (1967)] critically depends on the accurate determination of fundamental pitch period. Stover does not indicate that “… sensing the pitch rate of the speaker's voice …” is a crucial requirement of his system. However, it appears to this writer that reliable pitch detection plus the implied need for a voiced-unvoiced decision are the most difficult features to implement in his system.
Ultrasonic Relaxation of Hydrate Melts: System Ca(NO3)2⋅4H2O
Authors: Petrucci Sergio , Fittipaldi Fabio
Published: September 2005

Results of ultrasonic absorption of Ca(NO3)2⋅4H2O melts at temperatures of 45°, 50°, 60°, and 75°C are presented in the frequency range 5–170 Mc/sec. At 45°, 50°, and 60°C, a relaxation at (20±5) Mc/sec is observed. At 75°C, no relaxation is observed in the entire frequency range investigated. The volume viscosities are calculated and compared with the shear viscosities.
Circumferential Sound Pulses on Elastic Cylinders
Authors: Doolittle R. D. , McNicholas J. V. , Überall H. , Uginčius P.
Published: September 2005

We present a theoretical analysis of the diffraction of sound pulses on elastic cylinders in terms of circumferential waves. In particular, the speed of the pulse heads and the critical angles for entering and leaving the cylinder are obtained from causality arguments. Our conclusions are verified experimentally in the accompanying letter by Goodman et al.
Effects of Ultransonic Cavitation on Trypsin, α-Chymotrypsin, and Lactate Dehydrogenase Solutions
Authors: Macleod R. M. , Dunn F.
Published: September 2005

The denaturation of trypsin solutions by ultrasonic cavitation, reported by other investigators, has been confirmed. Similar studies on solutions of α-chymotrypsin and lactate dehydrogenase demonstrate that these enzymes are also denatured by ultrasonic cavitation.
Sound Absorption of Draperies
Authors: Batchelder James H. , Thayer William S. , Schultz Theodore J.
Published: September 2005

Measurements were made of the acoustical absorption introduced by various configurations of draperies into a small reverberation room. The results are presented and compared here.
Auditory Intensity Discriminal Scale I. Evidence Derived from Binaural Intensity Summation
Authors: Treisman Michel , Irwin R. J.
Published: September 2005

The problem of scaling the central effect of auditory stimulus intensity, I (in power units), is considered, and it is argued that there need not be a unitary neurophysiological correlate for “loudness.” Different psychophysical tasks may draw on different central measures of stimulus intensity. A “metric dimension,” L, which the subject may use in making quantitative judgments, is distinguished from a more peripheral “discriminal dimension,” E, involved in the immediate processing of the stimulus input. Binaural intensity summation data are used to derive the form of the function relating E to I, and it is shown that for any particular range of intensities this can be approximated by a power function, E = kIn, where the exponent n depends on the range of intensities used, approximating one near the absolute threshold and decreasing as over all intensity increases. On the assumption that with binaural stimulation the over-all loudness is determined by the sum of EL and ER, the effects produced by the stimuli to the left and right ears, linear equiloudness curves are obtained.
Multiple Scattering of Elastic Waves by Two Arbitrary Cylinders
Authors: Zitron N. R.
Published: September 2005

A perturbation method for the treatment of multiple scattering of acoustic waves by two arbitrary cylinders is extended to the case of elastic waves of plane strain. Interaction terms of monopole and dipole type are given explicitly.
Dynamic Response of Plates Due to Moving Loads
Authors: Raske Theodore F. , Schlack Alois L.
Published: September 2005

An analysis based on linear theory is presented for determining the dynamic response and the conditions of resonance for a simply supported rectangular plate acted upon by two types of moving loads corresponding to: (1) a point force of variable magnitude oscillating about a fixed position on the plate, and (2) a point force of constant magnitude traveling in a circular orbit about a fixed position on the plate. In addition to the ordinary resonance as produced by a variable magnitude load concentrated at a fixed position on the plate, resonance of the plate may occur due to the changing position of the load on the plate. It is shown that an infinitely countable number of load movement frequencies may excite a given principal frequency of the plate for the m, nth mode of vibration. Numerical examples of typical deflection profiles and time rate of deflection buildup are presented for two sets of initial conditions corresponding to: (1) a load initially at rest on the deflected beam, and (2) an accelerating load dropped from zero height on an initally undeformed beam.
On Optimum Baffles
Authors: Mangulis V.
Published: September 2005

The shielding properties of infinite strip and half-plane baffles are examined. The baffles may have different acoustic reactances on the opposite sides. The field in the shadow of the baffle is calculated as a function of the acoustic baffle reactances. For a plane-wave noise incident from behind the baffle and a plane-wave signal incident from the front, the signal-to-noise ratio is maximum when both sides of the baffle are pressure release surfaces.
N-Dimensional Partially Coherent Detection of an Accelerating Source
Authors: Schimmel H.
Published: September 2005

This article contains a discussion of correlation detection in which the coherent processing interval is limited by source/receiver accelerations and/or medium instabilities. A method is described, which, in effect, computes an n-dimensional correlation function uniquely related to target trajectory. Groups of relatively short waveforms that are individually insensitive to source accelerations, etc., are, after coherent reception, combined via pattern-recognition techniques. Curves are presented that give the processing gain of the method for various conditions. A numerical example is given for the sonar case.
Introduction to Acoustical Holography
Authors: Metherell Alexander F. , El-Sum Hussein M. , Dreher John J. , Larmore Lewis
Published: September 2005

The principle of reconstructed wavefronts is extended to the formation of visual pictures of acoustical waves. The important relationships used in conventional optical holography that also apply to acoustics are briefly reviewed. It is shown that image formation using the principles of acoustical holography yields better results than do conventional acoustical lens systems, particularly in the presence of turbulence and turbidity. Experiments are described in which coarsely sampled acoustical holograms, made with sound wavelengths of 0.64 in. and longer, have successfully reconstructed images of acceptable quality. The signal-to-noise ratio in a sampled acoustical hologram is shown to increase with the number of sampled points as well as with the reduction in the size of the sampling probe. Applications of acoustical holography in different fields are discussed.
Measurement of Room Absorption by Steady-State and Decay-Rate Methods
Authors: Huber Stanley F.
Published: September 2005

Steady-state and decay-rate methods of measuring A2, the total sound absorption in the receiving room of a transmission-loss experiment, were compared to determine how well they agreed. The results of a series of experiments under controlled laboratory conditions showed a very close agreement between the two methods, with differences averaging less than half a decibel ia measurements of 10 log10 A2. These results indicate that a steady-state method may be substituted for the reverberation-time method in measuring A2 without sacrificing the accuracy of laboratory measurements of airborne sound transmission loss of building partitions.
Model of the “Secondary” Residue Effect in the Perception of Complex Tones
Authors: Fischler Henryk
Published: September 2005

The phenomenon of tonal residue in stimulation of the hearing system by sinusoidally amplitude-modulated tones is examined for its correlation with the temporal fine structure displacements of the basilar membrane. It is suggested that the deviations of the residue pitch from magnitudes anticipated on account of the stimulus pattern at the input to the ear (in anharmonic complexes) represent a secondary effect only. Probably, these deviations arise from the phase modulation of the major carrier peaks of the resultant basilar-membrane displacements, evoked during passage of the stimulating signal to the cochlea. The phase modulation is due to asymmetry introduced the sideband energy of the stimulus as a result of the mechanical filtering by the inner ear. Representing a phenomenon in the time domain, the secondary residue effect is examined as a function of various compositions of the stimulating tone, at various locations along the basilar membrane. It is argued that the magnitude of the effect decreases with the harmonic-number relation between the carrier and modulation frequencies of the stimulus. Possibly, the region on the basilar membrane pertinent to characteristic frequencies lower than (but close to) the central component of the stimulating signal contributes most to determining the magnitude of the secondary effect.
Signal-Detection Theory Applied to Selective Listening
Authors: Moray Neville , O'Brien T.
Published: September 2005

Recently, two papers have appeared that have applied signal detection theory to selective listening. Both have certain defects, and the present paper is intended to clarify some of the issues raised by the earlier papers. Broadbent and Gregory (1963) used a tone detection task on one ear while presenting a memory load to the other and found that d′ but not β altered for the detection task. Treisman and Geffin (1967) recently reported on the “shadowing” situation (continuous repetition of an ongoing message) and again found evidence that d′ but not β was affected. Treisman interpreted her results to mean that selection of input, not of response, was operative, basing her conclusions on the way in which the subject responded to homophones and homonyms. Detection of signals was signaled by the subject tapping the microphone. Unfortunately, Treisman was forced to use pooled data for the estimation of d′ and β, which involved some strong assumptions about the relative performance of individual subjects. The present experiment was designed to provide a relatively “pure” selective listening task for the applicability of signal detection theory to the process of selective attention.
Application of Complex-Variable Theory to the Determination of the Fundamental Frequency of Vibrating Plates
Authors: Shahady Paul A. , Passarelli Ralph , Laura Patricio A.
Published: September 2005

This study deals with the determination of the fundamental frequency of vibration of plates of complicated shape. The method makes use of conformal mapping and variational techniques. In the case of a square plate, the results obtained are in good agreement with the exact values. Numerical results are also presented for a circular plate with two flat sides and several plates of regular polygonal shape.
Simple Method for Identifying Acceptable Noise Exposures
Authors: Botsford James H.
Published: September 2005

A simple method for identifying acceptable noise exposures has been developed from the NAS-NRC CHABA report describing hazardous exposures to intermittent and steady-state noise. First, an interrupted exposure was imagined in which the noise dropped to harmless levels periodically, thereby creating a number of identical exposure cycles distributed uniformly throughout the day. Next, the total duration of noise allowable per day was calculated for 39 different patterns of interrupted exposure using the CHABA graphs. This total noise duration permissible daily increased rapidly with the number of interruptions, passed through a maximum value for interruptions about 5 min in length, and became constant for noise interrupted every 2 min or oftener. Nine general contours of equinoxious octave-band sound pressure levels evolved from this analysis, and the A-weighted sound level equivalent to each contour was determined for noises of manufacturing industries. It is concluded that acceptable manufacturing-noise exposures can be identified as accurately by using A-weighted sound levels as is possible by using octave-band sound-pressure levels.
On the Rôle of Formant Transitions in Vowel Recognition
Authors: Lindblom B. E. F. , Studdert-Kennedy M.
Published: September 2005

An inventory of speechlike sounds was synthesized displaying systematic variations of the rate and direction of formant transitions. These sounds were specified by a set of vowel formant patterns selected along a continuum varying from [U] to [I] they were assigned to isolated, steady-state vowels, and to the points of zero rate of formant frequency change in symmetrical consonant-vowel-consonant syllables. The time variations of formant frequencies were made convex and concave by the choice of two consonantal frames: [w-w] and [j-j]. The results obtained in a series of vowel identification experiments indicate that a listener's categorization of the continuum varied as a function of the environment and the duration of the vowel. These findings suggest that, in the recognition of monosyllabic nonsense speech, the identity of a vowel is determined not solely by the formant-frequency pattern at the point of closest approach to target, but also by the direction and rate of adjacent formant transitions. In general, subjects adjusted their categorizations of the continuum in the consonantal contexts in such a way that complete transitions between loci and vowel target were not necessary: the transitions were permitted to undershoot the target frequencies for the vowel. In particular, the excursions of formants in the [w-w] syllables tended to be overestimated. Thus, there was a tendency for the categorizations to be made so as to compensate for the formant-frequency undershoot associated with vowel reduction [B. Lindblom, “Spectrographic Study of Vowel Reduction,” J. Acoust. Soc. Am. 35, 1773–1781 (1963)]. The effects observed are discussed in terms of an active model of vowel recognition, peripheral auditory analysis, distinctive features, and previously reported observations on vowel perception.
Multiple Relaxation in Gaseous Dibromomethane
Authors: Hageseth Gaylord T.
Published: September 2005

Sound-absorption measurements have been made in gaseous dibromomethane at a temperature of 296°K and at pressures between 10 and 31 mm. A traveling wave tube with a frequency range of 1000 to 4000 cps was used to determine the attenuation coefficient of the progressive waves. An anomalous absorption was found at an unusually low frequency and is attributed to a molecular relaxation process. (At least two other relaxations at high frequency are known.) A single relaxation curve fitted to the data points yielded a maximum intensity absorption coefficient per wavelength at 40 kcps/atm, which corresponds to a relaxation time of 4.6×10−6 sec. When hydrogen was added as an impurity, the absorption peak increased in magnitude but the relaxation time decreased only slightly. Based upon the specific heat contribution of each mode, two different modal assignments are possible in accounting for the multiple relaxations.
High-Temperature Ultrasonic Measurements of Rotational Relaxation in Hydrogen, Deuterium, Nitrogen, and Oxygen
Authors: Winter Thomas G. , Hill Garnett L.
Published: September 2005

The velocity and absorption of sound in normal hydrogen, deuterium, nitrogen, and oxygen have been measured from room temperature to 1000°C and from 0.7 to 40 MHz/atm. This frequency range encompasses the rotational relaxation of H2 and D2, but it is below the frequency of maximum absorption in N2 and O2. It was found that the frequency of maximum absorption always decreases with increasing temperature as predicted by Parker, and just the opposite of vibrational relaxation behavior. Absorption measurements on H2 at 22°C nearly fit a single relaxation curve, but the 800°C data show that multiple relaxations must exist. The frequency of maximum absorption shifts from 13 MHz/atm at 22°C to 5 MHz/atm at 800°C in H2, and from 15 MHz/atm to 4 MHz/atm in D2. While it was not possible to cover the entire absorption region in N2 or O2, single relaxation theory fitted to the available data indicates that the frequency of maximum absorption of both gases is approximately the same and shifts from above 300 MHz/atm at 23°C to 45 MHz/atm at 1000°C.
Radiative Damping of Sound Waves
Authors: Stein Robert F. , Spiegel E. A.
Published: September 2005

The classical investigation of radiative damping of sound waves by Stokes is generalized to the case of arbitrary ratio of acoustic wavelength to photon mean free path.
Damped Response of an Elastically Connected Double-Beam System Due to a Cyclic Moving Load
Authors: Kessel P. G. , Raske T. F.
Published: September 2005

The damped response of an elastically connected double-beam system due to a moving-point load that oscillates longitudinally along one of the members about a fixed point is examined analytically. The deflection equations are determined for a damped double-beam system for two cases: (1) the beams have individual damping, and (2) damping is introduced as a function of the relative velocity of the two beams. The analysis shows the relative importance of the infinite number of load movement frequencies that will excite a given principal frequency of the system for the rth mode of vibration. Numerical results are presented for the two cases for both equal and unequal beams and show the effects of damping, frequency of oscillation of load movement, amplitude of load movement, and modulus of the elastic connectors on the dynamic deflections of the system. The results also show the ability of the system to act as an elastic vibration absorber.
Analysis of Musical Sounds by Fourier Transform Methods
Authors: Metzger Eli
Published: September 2005

It is proposed that, since musical sounds are never periodic—if for no other reason than the fact that they are of finite duration—they should be analyzed by a Fourier integral rather than series. A continuous frequency spectrum results, whose width is larger the shorter the tone is. The effect of this frequency spread is examined for two tones, a finite sine, and an exponentially decayed sine.
Transitions in American English /s/ as Cues to the Identity of Adjacent Stop Consonants
Authors: Schwartz M. F.
Published: September 2005

A study was designed to investigate the role of perceived changes is /s/ as cues to the identity of adjacent stop consonants. Ten normal-speaking young adults recorded the words last, rasp, and task on a high-quality tape system. Three copies were made of the recording. Two of the copies were subjected to an editing procedure: in one, the final release was removed from each word; in the other, the /s/ as well as the release were removed. Each of the copies was presented, via loudspeaker, to a separate group of 10 normal-hearing young adults who were instructed to listen to the stimuli and to transcribe what they heard, using phonetic notations, The results indicated that perceived changes in /s/ were important cues to the Identity of /p/ and /k/, but not /t/.
Predicting Shallow-Water Transmission Loss
Authors: Cole Bernard F.
Published: September 2005

The applicability of ray theory for predicting shallow-water propagation loss at sonar frequencies is discussed.
Analog Systems for Analyzing Infrasonic Signals Monitored in Field Experimentation
Authors: Fehr Uri , McGahan L. C.
Published: September 2005

Large quantities of ultra low-frequency acoustic data accumulated over long periods of time can be analyzed by several methods. Preliminary analysis of the analog waveform determines specific areas of primary interest prior to digital-computer analysis. Data of no consequence can be discarded; or, the worth of such data may be graded, to scale their importance for computer processing. This technique also provides a means of expediting initial findings, and primary conclusions can be deduced. This study was conducted by the University of California, Los Angeles, and entitled, “Ionospheric Disturbance Experiment.” The raw tape-recorded data are played back through an electronic system. Some important parts of this system are narrow bandpass filters and a Missilyzer (sound spectrograph). Some sample results are summarized.
Systems and Methods in Statistical Analysis and Reduction of Geoacoustical and Geomagnetic Data
Authors: Fehr Uri , Tolman Wallace F. , Crolene Robert
Published: September 2005

Geo-acoustical and geomagnetic data gathered by an array of sensors for long periods of time were recorded on magnetic tape in frequency-modulated form. A new digitizing system was worked out for an accurate study, then data were reduced and adjusted (or “recolored” in the time domain) using a numerical-analysis technique, which corrects for frequency attenuation due to the frequency-response characteristics of the sensor and field recording equipment. Wavelength and wave velocity depended on frequency and statistical error estimated from study of the F-1 engine. The mathematical techniques involved in recoloring and filtering are explained, and the statistical techniques (autocovariance, cross covariance) used in the time-series analysis are discussed.
Ultrasonic Absorption in Carbon Dioxide-Water-Vapor Mixtures
Authors: Higgs Roland W. , Torborg Ralph H.
Published: September 2005

The absorption of ultrasound in CO2-H2O mixtures at 150° and 200°C was measured at frequencies of 1.25, 3.3, 4.8, 9.9, and 14.0 MHz for H2O vapor concentrations from 0.5% to 50%. The measured absorptions are compared with calculated results and agree reasonably well. The effect of H2O vapor on the relaxation frequency is linear at least up to 20% H2O vapor and a decrease in relaxation frequency is observed with increasing temperature.
Acoustic Absorption and Dynamic Viscosity in a Long-Chain Polymer
Authors: Hunter J. L. , Derdul P. R.
Published: September 2005

The acoustic absorption has been measured in the ♯200 series of silicones (linear polysiloxanes) over the frequency range 30–350 MHz, and the temperature range −30° to +30°C. The results are compared to measurements of dynamic viscosity made in the same fluids by Barlow, Harrison, and Lamb in approximately the same experimental region. It is found that a knowledge of the dynamic viscosity enables one to predict, quite precisely, the value of the acoustic absorption coefficient. The negligible volume viscosity and surprisingly low values of acoustic absorption and dynamic viscosity in this experimental range are discussed in terms of the theories of Rouse and Zimm for polymeric liquids of very long chain length.
Reflection and Transmission of Oblique Plane Waves at a Plane Interface between Viscoelastic Media
Authors: Cooper Henry F.
Published: September 2005

The solution is obtained for the reflection and transmission of time harmonic plane dilatational or shear waves at a plane interface between two linearly viscoelastic materials. Except in special cases, the reflected and transmitted waves are general plane waves, i.e., plane waves whose amplitudes vary across their wave-fronts. The angles of reflection and transmission depend on the incident angle in a more complicated way than in the limiting elastic case because the wave speeds of the reflected and transmitted waves are, in general, functions of the incident angle. Necessary and sufficient conditions for the existence of interface waves are obtained. It is found that no interface waves can exist for some materials. For another class of materials, interface waves exist for discrete angles of incidence. For still other materials, interface waves exist for all incident angles greater than some critical angle.
Multimode Response of Panels to Normal and to Traveling Sonic Booms
Authors: Crocker Malcolm J.
Published: September 2005

A detailed theoretical study of the response of a uniform flat rectangular panel to a sonic boom (or “N” wave) is presented. Both cases, where the N wave arrives normal to the panel surface and where the shock front arrives at any angle of incidence and crosses the panel parallel to one side, are considered. Closed-form solutions (for individual modes) are given for the cases of simply supported panel response to normal and traveling N waves; an approximate solution is presented for the response of a panel with fully fixed edges to a normal N wave. The Duhamel integral method used gives panel displacement-, strain-, and stress-time histories for any point on the panel. The analyses derived have engineering applications in the computation of window or wall-panel response to sonic boom. Some comparison made between theory and experiment. Good agreement is shown to exist between measured and predicted strain maxima and fair agreement to exist between the early parts of the strain-time histories, despite some differences between the experimental and theoretical models. The necessity to include the contributions due to the higher modes is clearly borne out in theory and experiment, particularly for accuracy in strain-time histories.
Spatial and Spectral Dependence of Acoustic Reverberation
Authors: Anderson Victor C.
Published: September 2005

Reverberation data obtained in the latter part of 1966 at the northern end of the San Diego Trough are analyzed. Scattering coefficient distributions as a function of depth, horizontal displacement, and frequency are presented and compared with idealized normal distributions. Frequencies range from 8.0 to 9.5 kHz, depths from 100–3000 ft.
On the Equivalent Circuit of a Plane Wave Confronting an Acoustical Device
Authors: Bauer Benjamin B.
Published: September 2005

An approximate analog circuit of a plane wave confronting an acoustical device of aspect radius a is shown to comprise two in-phase voltages, respectively, having magnitudes of 2p and p and driving the device through a resistance ρc/A, and inductance 0.5 ρa/A.
On the Hertz
Authors: Young Robert W.
Published: September 2005

Attention is directed to omission of the unit of angular measure and mis-application of the period of a periodic function to a real exponential function that lead to the incorrect conclusion that the hertz is the same as the reciprocal second.
Ultrasonic Two-Dimensional Visualization for Medical Diagnosis
Authors: Kossoff George
Published: September 2005

In ultrasonic two-dimensional visualization, the spot size of the display unit is the limit of resolution and determines the design of the echoscope. The shortest echo response is obtained from a nonreflectivity backed transducer, but the usual backed or quarter-wave matched transducer gives adequate axial resolution. The beam-width of the optimum weakly focused transducer is equivalent to four times the spot size, and some form of signal comparison must be used to make the azimuthal resolution compatible with the axial resolution. The finite beamwidth also degrades the axial resolution of inclined structures and distorts the display by elongating structures along the beamwidth. Off-axis receiving transducers may be used to receive larger echoes from inclined structures. An improvement by a factor of 3 may be obtained before the employment of these transducers degrades the resolution. The technique is prone to artifacts that are more troublesome in contact than in water delay scanning. These features are illustrated for an echoscope designed for the visualization of the pregnant uterus.
Reverberation-Room Acoustics—Effects of Various Boundary Conditions
Authors: Knudsen V. O. , Delsasso L. P. , Leonard R. W.
Published: September 2005

An investigation of the sound field in a large reverberation room as influenced by a 2 in. mineral wool floor covering and or an array or 96 suspended plywood panels yielded significant results. The panels do not increase the decay rates, that is, their absorption is negligible, for frequencies below about 250 cps; their added absorption to the room increased progressively at higher frequencies to 24 sabins at 4000 cps. Decay rates for low-frequency single modes in the empty room were linear and ranged from 2.11 to 5.7 dB/sec; the decay rates when two contiguous modes were excited were very nonlinear; their contours were predicted in terms of the decay rates and the phase differences of the two modes. With the floor absorptive, the 96 panels reduced the maximal levels of impulsive sounds (pistol shots), at frequency below 250 cps.s, for all elevations above the floor; the average decrease was 4.6 dB. With the floor absorptive, the decay rate at 250 cps was only 6.2 dB/sec when source and microphone were in the upper part of the room, and 39.3 dB/sec when source and microphone were in lower part. The influence or these decay rates on the quality of recorded speech and music was shown to be large.
Vibrational Displacement and Mode-Shape Measurement by a Laser Interferometer
Authors: Deferrari H. A. , Darby R. A. , Andrews F. A.
Published: September 2005

Four experimental methods are described in a tutorial way for use with a laser interferometer in measuring vibrational displacements and mode shapes of a transducer face. The relative merits and experimental difficulties of the methods are discussed. Quantitative data to show the type of experimental agreement that one might expect between the various methods and two illustrative mode shape measurements are given. In general, by proper choice of one or more of the methods, displacement measurements of magnitude 0.1–6000 Å at sonic and ultrasonic frequencies can be made at a point 0.1 mm in diameter. Mode shapes are determined simply by moving the laser beam a measured distance between points. Displacement data presented show a random error for all methods of 5% in the range 0.5–80 Å and less than 5% above 80 Å.
Determination of Elastic and Piezoelectric Constants for Crystals in Class (3m)
Authors: Warner A. W. , Onoe M. , Coquin G. A.
Published: September 2005

Determination of the elastic and piezoelectric constants for crystals in class (3m) is complicated by the large number of independent constants and the many possible ways in which they may be combined. An experimental and analytical procedure has been developed to determine all the constants using primarily thickness-mode measurements made on small, plate-shaped samples of various crystallographic orientations, and results using this procedure have been obtained for lithium tantalate and lithium niobate, two recently developed synthetic crystals. The resonant and antiresonant frequency constants for thickness modes have been calculated as functions of a plate's rotation angle. Information in this form makes possible the selection of plate orientations that might be useful as resonators and transducers.
Physical Correlates of Brass-Instrument Tones
Authors: Luce David , Clark Melville
Published: September 2005

Time-dependent Fourier analyses of the attack transients and steady states of about 900 trumpet, trombone, tuba, and French-horn tones yielded the amplitudes and relative phases of the first 11 partials. Relative component amplitudes for all tones of an instrument played at a given dynamic marking are approximately described by a spectral envelope. The partials are conveniently divided into those below a cutoff frequency (Class 1 components) common to all notes of the instrument and those above it (Class 2). Class 1 components have similar attack envelopes and reach approximately equal steady-state values before those in Class 2. The transient periods for Class 2 components increase with frequency of the components, and their steady-state values decrease rapidly with increasing frequency of the components. Amplitude modulations (blips) that last for one or only a few cycles of the modulation occur for all components during the end of the transient, but are larger for Class 2 components. For brasses other than the French horn, spectral envelopes are approximately frequency-scaled versions of each other. Rolloff rates above the cutoff frequency decrease as the average amplitude of a scale of notes increases, and it appears that an increase in radiated power is achieved primarily by an increase in the amplitudes of high-frequency partials. Average rolloff rates in decibels per octave for scales played at an average sound pressure level of 68 dB were: trumpet, 15; trombone, 20; tuba, 17; unstopped horn, 16; stopped horn, 30.
Acoustical Analysis of a Multicylinder Engine Air-Induction System
Authors: Wang W. M.
Published: September 2005

By use of a time-varying volume representation for the cylinders, an acoustical equivalent circuit for a multicylinder engine air-induction system is developed, and a general solution for the acoustic pressure is derived. A commercial four-cylinder engine is used for a comparison between the analytical and experimental results. It is shown that the agreement is closer than when a conventional time-invariant equivalent circuit is used for the engine cylinders.
Scattering from the Time-Varying Surface of the Ocean
Authors: Parkins B. E.
Published: September 2005

The frequency spreading of a monochromatic acoustic plane wave reradiated by the moving, rough surface of the ocean is described using the spectral density of the far-zone reradiated pressure. This pressure is calculated using the method of physical optics for a surface assumed to be described by the Neumann-Pierson directional wave spectrum. The results are specialized for the cases of slightly rough and very rough wind-generated seas. For the slightly rough case, the spectral density contains a specularly reflected component at the frequency of the incident radiation and two monochromatic scattered components that are Doppler-shifted by equal amounts from the frequency of the incident radiation. The magnitude of the deviation of each of the Doppler-shifted frequencies is the same and depends on the angles of incidence and observation relative to the wind direction and also on the incident frequency. For the very rough surface case, the spectral density of the far-zone reradiated pressure is of Gaussian form. In the specular direction, the center of the spectrum is at the frequency of incident radiation but is shifted away from that frequency for other angles of observation with a shift proportional to wind speed. The width of the spectrum increases as the three-halves power of the wind speed and also depends upon the geometry.
Reflection of Circumferential Waves from a Slit in a Thin-Walled Cylinder
Authors: Goldsberry T. G.
Published: September 2005

Circumferential waves have been detected in a thin-walled air-filled brass cylinder having an air gap in the wall. The cylinder is 11.94 cm in diameter, 24.13 cm long, and has a wall thickness of 2.62 mm. The air gap, 1.57 mm wide, extends the thickness of the wall and almost the length of the cylinder. The cylinder was immersed in water for all acoustic measurements. Two circumferential wave modes, flexural and compressional, were detected and measured over the frequency ranges 125–150 kHz and 275–300 kHz, respectively. Under the assumption that the circumferential wave is reflected at the air gap, ray theory is used to derive equations predicting the location in time, relative to the specular echo, of the circumferential waves in the cylinder. Experimental evidence establishing the validity of these equations for both the compressional and flexural modes is presented.
Relations Among Aftereffects of Acoustic Stimulation
Authors: Harris J. Donald
Published: September 2005

In Expt. 1, six women were given 12 separate tests of short-duration auditory adaptation. Correlations among subjects showed that two subgroups existed, one pair differing from the others in exhibiting an interaction between stimulus strength/duration and slope of recovery. A battery of four tests is tentatively recommended that would sample the effects on different subjects of stimulus frequency, intensity, and duration, and of slope of recovery. In Expt. 2, 15 adults were given 47 tests of true auditory fatigue with pure tones. Previous data on temporary threshold shift (TTS) growth rates, equinoxious contours, recovery slopes, etc., were confirmed. An obverse factor analysis was performed, upon a correlation matrix not among tests but among subjects. A general-susceptibility grouping emerged; three individuals defined rather poorly a grouping with reduced high-frequency and increased low-frequency susceptibility; three other individuals showed recognizable specific patterns of susceptibility. Three specific tests can be shown to sample these groupings, and are recommended tentatively as an auditory fatigue battery for pure tones. Using a supplementary battery of 15 noise tests, a subgroup of three was sufficient to predict whole battery performance (r=0.81), as against a prediction (r=0.65) between any pure-tone combination versus the whole-battery noise data. Experiments 3, 4, and 5, used this information to study the prediction of susceptibility to noise-induced permanent threshold shift in man, rat, and monkey, respectively. A rather low level of success was achieved.
A Model for Auditory Discrimination and Detection
Authors: Henning G. Bruce
Published: September 2005

A modified energy detector is proposed as a predictor of human frequency- and amplitude-discrimination performance. The model consists of an initial bandpass filter followed by a square-law device and an integrator. The center frequency of the initial filter is assumed to be a random variable distributed over time. The predictions of the model for performance in two-alternative forced-choice frequency- and amplitude-discrimination experiments are presented, together with data from human observers. While the model is able to predict the frequency and amplitude data very well, it is less successful with detection data.
Asynchrony: The Perception of Temporal Gaps within Periodic Auditory Pulse Patterns
Authors: Pollack Irwin
Published: September 2005

The perception of temporal gaps within periodic pulse patterns was examined in a forced-choice test. The task of the listener was to identify which one of four pulse patterns contained a temporal gap. Extremely acute gap detection (in the region of 1–10 μsec) may be obtained with high pulse frequencies. Gap detection with high pulse frequencies is critically dependent upon the number of pulses; gap detection with low pulse frequencies is relatively independent of the pulse number. This result is consistent with the generalization, obtained in related studies, that extremely acute temporal discrimination is achieved at high pulse frequencies only with a large number of temporal samples, whereas the relatively poor temporal discrimination at low pulse frequencies is substantially less dependent upon the number of temporal samples. The temporal precision of the auditory system, in contrast with its precision of spectral analysis, appears to be insufficient to account for minimal gap thresholds.
Comments on “Interaction of the Auditory and Visual Sensory Modalities” [J. Acoust. Soc. Am. 41, 1–6 (1967)]
Authors: Morton John
Published: September 2005

In deriving an equation to test the independence of sensory processing systems, Brown and Hopkins (1967) appear to have built in an assumption of response patterns lacking generality. In addition, the performance of their subjects is in excess of predictions from alternatively derived independence models, as well as one derived from signal detection variables. These data can be accounted for only by assuming a high level of “internal noise.”
Brillouin Scattering: Viscoelastic Measurements in Liquids
Authors: Pinnow D. A. , Candau S. J. , LaMacchia J. T. , Litovitz T. A.
Published: September 2005

The theory of Rayleigh scattering from density fluctuations is applied to data taken in glycerol and n-butanol over wide temperature ranges. It is shown that Brillouin scattering is useful in evaluating the viscoelastic parameters of a liquid when all corrections are properly applied. The position, half-width, and intensity of the Brillouin lines as well as the total intensity are the main features of the spectrum used. The definition of the Landau-Placzek ratio was generalized to be applicable to relaxing liquids and glasses and its behavior was studied over a 200°C temperature range in glycerol. The hypersonic data indicate that at high temperatures (∼70°C) in glycerol the distribution of relaxation times is narrower than that ultrasonically found at lower temperatures (∼−10°C). This result is in agreement with the concept that the origin of the distribution is related to cooperative behavior which is less pronounced at higher temperatures.
Instrumental Effects on Brillouin Line Shapes
Authors: Leidecker H. W. , LaMacchia J. T.
Published: September 2005

Instrumental distortions of the Brillouin light spectrum induce systematic errors into the observed sound velocity and sound absorption. A model is given by which certain distortions may be reduced. The model involves Voigt functions, which are a generalization of Gaussian and Lorentzian functions. It is shown that corrections in general involve both an instrumental linewidth and a parameter which measures the line shape of the instrumental spectrum.