bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Brief Loud Noise on Decision Making
Authors: Woodhead Muriel M.
Published: September 2005

An experiment was designed to investigate whether irrelevant loud bursts of low-frequency noise affected decision-making unfavorably. Analysis of the results revealed a significant decrement in performance due to the noise distraction. Scores for the whole of a 4-min test were unimpaired because only those responses immediately following the noise were affected. A second experiment demonstrated that effects were related to intensity.
Hydrostatic Balancing Mechanism of Xenopus Larvae
Authors: van Bergeijk Willem A.
Published: September 2005

Experiments are described which show that larvae of the South African clawed toad Xenopus possess a reflex mechanism which enables them to maintain a stable position in the water, independent of hydrostatic pressure. From observations on the behavior of the animals and recordings from the saccular macula of the ear, the conclusion is drawn that the lung of the animal generates an ac signal, which is frequency modulated by the hydrostatic pressure. This signal is transmitted to the ear, and is utilized to maintain balance. A conceptual model for the reflex is proposed.
Use of Pressure Gradient Receivers in a Correlator Receiving System
Authors: Jacobson Melvin J. , Talham Robert J.
Published: September 2005

An analysis is made of a steerable correlator receiving system which contains two directional receivers of the pressure gradient type. The axes of the receivers are oriented in the broadside direction. The output signal-noise ratio is computed and compared with that of a system employing two omnidirectional receivers. The directional receiver system gives a maximum improvement in output ratio for broadside signal sources which increases as the orders of the receivers increase. The range of improvement over source direction is also studied. Other results include the fact that the maximum output signal-noise ratio of the directional receiver system containing two receivers of order 1 (2,3,4,⋯) is equal to that of an array correlation system requiring the use of 6 (10,14,18,⋯) omnidirectional receivers.
Vowel Overlap as a Function of Fundamental Frequency and Dialect
Authors: Brubaker Robert S. , Altshuler Morton W.
Published: September 2005

Two groups of young adult male college students spoke the syllables /∫ɛp/ and /∫æp/ under two conditions which differed in that vowel fundamental was controlled at 130 ± 5 cps in one condition. One group spoke the General American dialect while the second group spoke a subdialect, that of Altoona, Pennsylvania. Spectrographic recordings of the utterances were analyzed and the center frequencies of the lower two formants plotted. The plots of the two vowels were analyzed and the extent to which they overlapped described.

Within the limitations of this study, the results indicate that control of the speaker's vocal fundamental does not reduce vowel overlap, while controlling the subdialect of the speaker does reduce the percentage of overlapping. While overlap is decreased it is not eliminated, and it is probable that vowel discrimination is accomplished by means of cues additional to the frequency locations of the lower formants.
Spherical Waves of Finite Amplitude
Authors: Fay R. D.
Published: September 2005

A method is presented for the analysis of spherical waves of finite amplitude. An example of the application of the method is given for the case of repeated shock waves.
Measurement of Sound Diffusion in Reverberation Chambers
Authors: Schroeder Manfred R.
Published: September 2005

This paper describes a variety of methods for the measurement of the diffusion of sound fields in reverberation chambers. Diffusion is defined on the basis of the angular distribution of sound energy flux, in accordance with the definition that has found its visual expression in the “sound hedgehog” of Meyer and Thiele. The theoretical foundations of the methods proposed here are: normal mode expansion, the sampling theorem (both in time and two-dimensional space), and either Fourier or correlation analysis. The quantities to be measured are sound pressures and, in some cases, sound pressure gradients at a number of sampling points on the measuring wall. Results of these measurements are suitably transformed to give the sound energy fluxes for all possible angles of incidence. The accuracy of measurement is determined by the Q (frequency times reverberation time) of the chamber and is typically of the order of 1°. This extra-ordinary directivity is achieved without substantial perturbation of the sound field. Methods applicable to both single frequencies and finite frequency bands are described.
Noise Stress in Laboratory Rodents. I. Behavioral and Endocrine Response of Mice, Rats, and Guinea Pigs
Authors: Anthony Adam , Ackerman Eugene , Lloyd James A.
Published: September 2005

Mice, rats, and guinea pigs were exposed daily to high intensity noise in the frequency range of 150–4800 cps at a sound pressure level of about 140 db, re 0.0002 μbar. It was found that the behavioral and endocrine responses differ in the three species studied. The adrenal response of animals exposed to noise supports the interpretation that noise acts as a physiological stress, but does not induce harmful extra-auditory effects. Thus, the endocrine system appears to act as a multiloop feed-back system which compensates for the effects of noise on the central nervous system.
Role of Interaural Time and Intensity Differences in the Lateralization of Low-Frequency Tones
Authors: Moushegian George , Jeffress Lloyd A.
Published: September 2005

There has recently been a renewal of interest in the roles of intensity and time in the lateralization of sounds. The technique generally employed is to offset the effect of an interaural time difference in one direction with a difference of level in the opposite. In the present series of experiments a different method was used, that of having the subject adjust the interaural time relation for a noise until it appears to be in the same lateral position as the stimulus tone. Using this procedure, we have obtained results which support the findings of other recent workers that increasing the intensity of the stimulus to an ear will cause it to transmit earlier in time. We have found additional evidence, however, which shows that the central nervous system, too, responds to interaural intensity differences, and that its response is different from that of the peripheral system. When time and intensity are opposed, time has less effect on it than when time and intensity both favor the same side.
Propagation of a Pressure Pulse in a Compressible Flow
Authors: Powell Alan
Published: September 2005

A one-dimensional treatment of the propagation of a pressure pulse through a channel carrying a compressible flow is given. The method consists of summing the multiple linear reflections of increasing order, the “transmission” and “reflection” coefficients then being given in the form of power series whose terms depend only on the entry and exit Mach numbers of the mean flow. The series fails to converge under certain circumstances, but there is nothing corresponding to this in the equivalent results obtained from “before” and “after” steady-state considerations. Both methods are shown to fail at a sonic throat, where it is suggested that the assumption of one-dimensional perturbations is no longer tenable.
Measurements of Acoustic Radiation Force
Authors: Budal K. , Hoy E. , Olsen H.
Published: September 2005

The acoustic radiation force of a plane wave impinging on a rigid sphere of diameter 10 cm and on a circular disk of diameter 7.4 cm has been measured in the wavelength interval 4 to 40 cm. The agreement with theory is satisfactory.
Lateralization Threshold as a Function of Stimulus Duration
Authors: Tobias Jerry V. , Zerlin Stanley
Published: September 2005

Measurement on experienced listeners of interaural time difference (ITD) thresholds for wide-band random noise indicates that the threshold varies systematically with duration of stimulation. In order to determine the point at which increase duration no longer decreases ITD threshold, stimulus (noise burst) duration was varied between 0.01 and 1.94 sec. A given ITD was maintained throughout any particular burst, starting time included. All stimuli were presented at a level of 65 db SPL to each phone. The “duration” versus “ITD threshold” function reaches asymptote at approximately 0.7 sec, indicating that the binaural system which effects the comparison necessary for a lateralization judgment may integrate information over that period for the kind of stimulus used.
Interaural Noise Correlations: Examination of Variables
Authors: Pollack Irwin , Trittipoe William
Published: September 2005

The identification of interaural noise correlations was examined as a function of the: duration, sound level, frequency range, and interaural balance of the noise. Progressive changes in identification performance were observed with changes in the individual variables.
Detecting Sound Fields
Authors: Bordone Sacerdote C.
Published: September 2005

A feedback method is described, permitting a loudspeaker to be driven automatically so that the sound pressure generated at any one point is constant with frequency, independent of the loudspeaker characteristics. Several applications illustrate the success of the method in the calibration of microphones and in the study of diffraction and reflection effects.
Effect of Jet Structure on Noise Generation by Supersonic Nozzles
Authors: Mull Harold R.
Published: September 2005

In this study the near noise field of a supersonic jet (Mach 2.87), exhausting into quiescent air, is analyzed with respect to the aerodynamic structure of the jet. The noise field is shown to be shifted away from the jet exit with the most intense sound near the end of the supersonic portion of the exhaust structure. Downstream of this point, the jet radiates noise in the same manner as a subsonic jet.
Correction for Diffraction Losses in the Ultrasonic Field of a Piston Source
Authors: Papadakis Emmanuel P.
Published: September 2005

In ultrasonic attenuation experiments carried on by the pulse method, it is important to know the part of the measured attenuation contributed by diffraction in the ultrasonic field. In certain cases, particularly at the lower megacycle frequencies, the diffraction loss can be much greater then the attenuation intrinsic to the specimen. The diffraction loss in decibels has been computed elsewhere as a function of the distance the ultrasonic pulse travels back and forth in the sample. Here an expression for the increment to the attenuation is derived taking into consideration which echoes the decibel drop is measured. It is shown that the first echo has suffered a considerable loss at the lower frequencies and that one must consider that loss in computing the increment to the attenuation caused by diffraction if he has used that echo as one at which the decibel loss is measured. If that loss is not considered, the incremental attenuation will be excessive.
Velocity of Ultrasonics in Halogen Vapors
Authors: Richardson E. G.
Published: September 2005

The limiting values of the velocity of sound for high and low frequencies in the halogens in the gaseous state have been calculated. Measurements at ultrasonic frequencies in three gases have confirmed dispersion of the velocity with relaxation times in the vicinity of 10−6 sec.
Onset of Ultrasonic Cavitation in Tap Water
Authors: Strasberg M.
Published: September 2005

The conditions influencing the onset of acoustically-induced cavitation in tap water have been investigated, with special attention to the effect of air-filled cavitation nuclei. Cavitation was induced by exciting an acoustic radial mode in the water in a spherical resonator at a frequency near 25 kc/sec. Air-filled nuclei were detected by observing the reverberant decay of sound in the resonator at frequencies from 150 to 550 kc/sec, the presence of air nuclei causing an increase in the decay rate.

Measurements have been made of the sound pressure required for cavitation inception, and of the content of air nuclei, for the following treatments of the water: (1) allowing the water to stand undisturbed after drawing from the tap, (2) partially deaerating the water, and (3) subjecting the water to increased static pressure. Some measurements were also made of the threshold for rectified diffusion into air bubbles.

The experimental results have been compared with theoretical predictions based on three alternate forms of air nuclei: (1) free air bubbles, (2) air trapped in cracks on suspended solid particles, and (3) air bubbles surrounded by skins of organic impurities.
Absorption of Sound Arising from the Presence of Intact Cells in Blood
Authors: Carstensen Edwin L. , Schwan Herman P.
Published: September 2005

The absorption of sound in blood occurs primarily on a molecular level and is related to the presence of protein in the cells and plasma. However, a small contribution to the total absorption arises simply from the presence of intact cells in the blood.

Analysis based on Epstein's theory of scattering shows that the cellular absorption results from a viscous interaction between the fluid and cells when the latter, because of their greater density, fail to follow the oscillatory motion set up by the sound wave.
Geometrical Theory of Diffraction in Inhomogeneous Media
Authors: Seckler Bernard D. , Keller Joseph B.
Published: September 2005

The geometrical theory of diffraction is described. It is used to determine the diffracted fields in inhomogeneous media. Cases in which such media contain smooth convex bodies are treated. The theory employs an extension of Fermat's principle which yields diffracted rays. By energy considerations the field associated with each ray is calculated. This calculation requires the introduction of diffraction coefficients and decay exponents. General formulas for these quantities are given in terms of local properties of the medium and of the body.

In the companion article “Asymptotic theory of diffraction in inhomogeneous media” these problems are considered as boundary value problems. They are solved exactly and the solutions are expanded asymptotically for high frequencies. In all cases the asymptotic expansions agree completely with the corresponding results derived by the geometric theory, thus verifying this theory.
Direct Measurement of the Acoustic Ratio
Authors: Stroh W. Richard
Published: September 2005

A direct measurement of the acoustic ratio Q—i.e., the ratio of reverberant sound energy density in an enclosure to the direct sound energy density—by a correlation technique is shown to be possible. Results of such measurements in several rooms are found to agree fairly well with values obtained from the reverberation time through the formula Q = 4πTR2/13.8V, which is based on the Sabine theory of the diffuse reverberant sound field.
Residual Effects at Longer Pre-Exposure Durations
Authors: Trittipoe William J.
Published: September 2005

The lower limit of intensity for demonstrating residual effects at low noise levels is a decreasing function of the pre-exposure duration.
Imbedded Thermistor for Boundary Layer Measurements
Authors: Gould R. K. , Nyborg W. L.
Published: September 2005

A technique, involving use of a thermistor imbedded in a plane surface, is described for measuring viscous heating and microstreaming in acoustic boundary layers.
β-Quartz as High-Temperature Piezoelectric Material
Authors: White Donald L.
Published: September 2005

Beta-quartz, the high-temperature form of quartz, which exists from 573°C to 850°C, is examined for use as a piezoelectric device. The formulas for the piezoelectric constants and elastic constants are given for rotated reference frames. By suitably rotating the crystal plate, it is possible to piezoelectrically excite lengthwise extensional, face shear and thickness shear modes of vibration. Thickness extensional modes cannot be excited. It is thus possible to make both high- and low-frequency piezoelectric resonators and transducers out of β-quartz for very high temperature applications.
On Propagation of Waves in Slightly Rough Ducts
Authors: Samuels J. Clifton
Published: September 2005

The problem of the propogation of harmonic signals in a slightly rough duct is investigated. The analysis made tractable by the assumption that the heights of the roughness peaks are small compared to the average separation of the duct walls. Both acoustic and electromagnetic waves are treated. In the case of a duct with harmonic roughness, it is found that waves are not scattered upstream if the frequency of the transmitted signal exceeds certain critical values related to the natural modes of the wave guide and the wavelengths of the wall roughness. It is also found that the scattered signals are amplified whenever the frequency of the transmitted signal is equal to any of a series of critical frequencies determined by the natural modes of the guide and the spectrum of the wall roughness. Statistically rough walls are also treated, and specific results worked out for roughness functions having Dirac delta function correlation exponential correlation.
Action of the Middle Ear Muscles in Normal Cats
Authors: Galambos Robert , Rupert Allen
Published: September 2005

Wires have been permanently implanted on the round window of the cochlea in cats. The voltage output of ears responding to sound stimulation has thus been made continuously available in unanesthetized animals for periods up to 4 months. By cutting the middle ear muscles of one ear and comparing its responses with those derived from the normal ear on the opposite side, it has been shown that the muscles: (1) do not appreciably influence absolute sensitivity, (2) contract to intense stimuli within 15 msec of their delivery to either ear, (3) attenuate transmission of tones between at least 500 and 3000 cps, and (4) significantly protect the ear against damage from intense sounds. Spontaneous contractions sporadically and intermittently introduce a transmission attenuation of several decibels in the resting normal cat. The stapedius muscle is much more important than the tensor tympani in producing these effects.
Responses of the Auditory Cortex to Repetitive Acoustic Stimuli
Authors: Goldstein M. H. , Kiang N. Y.-S. , Brown R. M.
Published: September 2005

Electrical responses to low-intensity repetitive clicks and bursts of noise were recorded from the cat auditory cortex. Responses decrease in size as the repetition rate is increased, and for rates higher than 50/sec are smaller than the “ongoing” activity of the cortex and become difficult to detect visually. An electronic average response computer was used to detect responses to high rates of stimulation. Stimulus-locked responses to clicks and bursts of noise were found for rates up to 200/sec in unanesthetized cats, but only up to 100/sec after anesthetization.
Intelligibility of Reiterated Speech
Authors: Sharf Donald J.
Published: September 2005

An attempt is made to increase the intelligibility of speech sampled in time (interrupted speech) by filling in the blank spaces with repetitions of the speech samples (reiterated speech). The experiment involves the evaluation of these processes of speech distortion in quiet and in noise with two duty cycles (speech-time fractions), with various rates of interruption of the speech signal, and with various buildup and decay times in the switching operation. The results indicate that (1) there is little difference between the intelligibility of reiterated speech and interrupted speech in quiet, (2) reiterated speech is more intelligible than interrupted speech in noise if signal measurements are based on instantaneous amplitudes of the speech samples, and (3) buildup and decay has little effect on the intelligibility of interrupted speech when the entire buildup phase is confined to the “on” time of the switching period.
Strain Gauge Measurement of Output of Magnetostrictive Ultrasonic Transducer—Pitfalls of Optical Measurement
Authors: Lamport Harold , Zinsser Hans H.
Published: September 2005

An easily fabricated, bifilar wire strain gauge wound helically about the hilt of an ultrasonic magnetostrictive transducer measures amplitude faithfully and is more convenient than optical methods. Pitfalls in the usual optical method are illustrated and discussed.
Velocity and Attenuation of a Narrow-Band, High-Frequency Compressional Pulse in a Solid Wave Guide
Authors: Redwood M.
Published: September 2005

The usual solutions describing the propagation of continuous waves in solid plates and cylinders fail to predict the observed velocity and attenuation, and secondary signals, in the propagation of a narrow-band pulse of compressional waves of carrier frequency of the order of 10 Mc/sec. It is shown that all these factors may be accounted for if a slightly different form of solution is chosen, to fit more closely the conditions under which the propagation takes place. Both plates and cylinders are treated theoretically, and methods of obtaining approximate solutions of the modified frequency equations are discussed.

The results of this analysis agree closely with those derived by other, less exact methods, which commence with the assumption that the solid medium behaves very similarly to a fluid.

The relation of this work to the propagation of pulses at low frequencies is also discussed.

A method of analysis similar to that employed here is also necessary to predict experimental results in the propagation of pulses in multilayered wave guides of any configuration, mechanical or electromagnetic.
Correlation of a Finite Distance Point Source
Authors: Jacobson Melvin J.
Published: September 2005

A two-receiver steerable correlation system intended to process signals from point sources at a large distance from and in a common plane with the receivers will give a predicted source direction which is generally different from the actual source direction when the source distance from the receivers is not large. The exceptions are broadside or end-fire sources for which the predicted and actual directions are equal. Apart from these cases, the predicted direction is always closer to broadside than the actual direction. Other results include the fact that a given predicted direction corresponds to a source location at any point on a corresponding hyperbolic arc.
Siren Design for Producing Controlled Wave Form with Amplitude Modulation
Authors: Allen C. H. , Watters B. G.
Published: September 2005

A siren has been developed which permits the generation of a sound pressure wave with harmonics more than 15 db below the fundamental over a broad frequency range and over a range of power output exceeding 40 db. The large dynamic range was obtained by the use of a shutter which changes the maximum open area of the siren ports and simultaneously alters the time variation of area so that the output signal remains substantially sinusoidal at any shutter position. The shutter can be operated rapidly to provide a means for programed amplitude modulation of the output signal with a minimum of harmonic distortion.
Intensive Differential Thresholds for Octave-Band Noise
Authors: Small Arnold M. , Bacon W. Edward , Fozard James L.
Published: September 2005

This study investigated the effects of 4 band widths of noise of different center frequencies presented at three sensation levels on the size of the differential threshold (ΔI) for intensity. Eleven untrained subjects and three trained subjects served in a study employing the method of limits. Analysis of the data showed that ΔI's for a low octave band (127–225 cps) of noise were larger than those for a middle octave band (1040–2080 cps) and high octave band (4080–8160 cps) of noise. The middle and high bands in turn yielded ΔI's that were larger than those for a wide-band noise. The magnitude of the ΔI's for the octave noise bands were tentatively related to the average ΔI for those frequencies contained in the band. Comparison of the ΔI's for wide-band noise to those obtained by other experimenters showed close agreement.
Temporary Threshold Shift from Octave-Band Noise: Applications to Damage-Risk Criteria
Authors: Ward W. Dixon , Glorig Aram , Sklar Diane L.
Published: September 2005

The growth and recovery of TTS in normal observers following exposure to octave-band noise is shown to follow the same course as that after broad-band noise: both are linear in log time. Rate of growth varies with frequency of exposure band and test frequency, being greatest at 4 kc following exposure to 2400–4800 cps or 1200–2400 cps, less at lower test frequencies and octave bands. The time for total recovery apparently is a function of the initial TTS. The results support present damage-risk criteria for continuous noise, which (1) suggest ear protection when octave-band levels exceed 85 db SPL and (2) require it in levels above 95 db SPL.
Compressional Relaxation in Liquids
Authors: Nettleton R. E.
Published: September 2005

A set of phenomenological equations, valid at all frequencies, is proposed for the rates of change of internal relaxation parameters describing molecular excitations and structural changes in liquid. An Onsager coupling is found to exist between the rate equations for the parameters and the pressure tensor, so that the diagonal terms of the pressure contain a linear sum of thermodynamic affinities governing the internal irreversible processes. These affinities can be eliminated from the pressure, using the rate equations, to give a complex compressional modulus, reducing to a bulk viscosity term at low frequencies and a contribution to the bulk modulus at very high frequencies. The bulk viscosity is calculated at 20°C for two nonassociated liquids, on the assumption of a single thermal and single structural relaxation time, with use of a “hole” model of structural relaxation based on a shear viscosity theory of Mooney. The acoustic absorption coefficient is computed from the bulk viscosity, yielding fair order-of-magnitude agreement with experiment in both cases.
Inextensional Vibrations of a Sphere-Cone Shell Combination
Authors: Saunders Herbert , Paslay Paul R.
Published: September 2005

The Rayleigh inextensional theory for thin shells is employed to predict the natural frequencies of a sphere-cone combination. For a particular case, the calculated and measured natural frequencies of shells of nonuniform thickness are determined. In comparing the experimental values of the lowest five “bell” frequencies with the predicted theoretical inextensional theory, there is very good agreement. This indicates that the method may be used for many missile configuration and jet engine applications.
On the Lambda Loudness Function, Masking, and the Loudness of Multicomponent Tones
Authors: Garner W. R.
Published: September 2005

A computational procedure is presented for determining the loudness of multicomponent tones. The procedure uses the lambda loudness function and has just two basic assumptions: (1) loudness of components add as the sum of their squares, and (2) the effect of masking is to subtract a constant amount of loudness. With these two assumptions, the loudness data of Fletcher and Munson for multicomponent tones are predicted, using the lambda function and the masking data of Wegel and Lane for the necessary predictive terms. This procedure gives better accuracy than the original calculational schema of Fletcher and Munson, even though no constants are determined from the data. In fact the three sets of data (loudness scaling, masking, and multicomponent loudness) can be used such that any two will correctly predict the third. It seems possible that the lambda function may provide better integration of auditory data than other loudness functions.
Analysis of a Piezoelectric Phonograph Transducer as a Function of the Clamping Position
Authors: Howling D. H.
Published: September 2005

A laterally vibrating piezoelectric phonograph transducer is analyzed by treating the transducer as a transmission line. The effect of clamping the crystal at any point is simulated by introducing into the line at the corresponding point a capacitance whose value is related to the compliance of the clamp. The record load appears as a terminating impedance at the end of the line. Several response curves corresponding to different loading and clamping positions have been determined from the electrical analogy for both playback and record.
Synthesis and Perception of Nasal Consonants
Authors: Nakata Kazuo
Published: September 2005

The generation of nasal consonants can be simulated approximately by a cascade connection of simple electrical tuned circuits excited by a quasi-periodic electrical buzz source. The lowest resonance for nasal consonants is in the vicinity of 200 to 300 cps, and the damping of this resonance is greater than that for the first resonance of vowels. A terminal-analog synthesizer and control device have been used to generate a number of synthetic syllables, each consisting of a nasal consonant followed by a vowel, with smooth formant transitions between consonant and vowel portions. Systematic listening tests have shown that the identification of the nasal consonant is determined largely by the frequency position of the second resonance of the nasal portion of the syllable, and thus by the direction and extent of the second formant transition of the vowel, as noted in other studies. The identification of the nasal consonant is also dependent to some extent on the duration of the consonant and transition portions of the syllable. Isolated nasal consonants generated by this procedure can also be identified with reasonable consistency.
Observations on Resolution and on Field Variations in Near Field Sonic Optical Systems
Authors: Suckling E. E.
Published: September 2005

The author is working towards the development of an ultrasonic viewing system which is an analog in ultrasound of conventional light photography. In the present paper it is shown that a sonic lens is able to resolve two sources of ultrasound whose spacing is about equal to the length of one wave of the sonic energy in use. It is also shown that at the frequency being used (3 Mc) uniform illumination of an object for sonic viewing is very difficult because Fresnel near field and other diffraction and interference effects occur very readily and that these effects are frequently themselves not stable.
New Wall Design for High Transmission Loss or High Damping
Authors: Kurtze G. , Watters B. G.
Published: September 2005

A typical single wall is characterized by a free flexural wave speed, cB, which increases with ω12. When cB approaches c0 (the speed of sound waves in the surrounding medium) the impedance of the wall to incident sound wave ceases to be mass-like because of the coincidence effect and the transmission loss will be less than that given by mass law. Since cB = (B/M)12(ω)12 for homogeneous walls, the deleterious effects of the coincidence of the flexural wave speed with the phase velocity of sound in the medium can be avoided for homogeneous walls by reducing the ratio of B/M. (B is the dynamic bending stiffness of the wall; M is the mass per unit area of the wall.) Thus the problem of good acoustical performance in homogeneous walls is seen to be in essential conflict with the need for structural rigidity.

A new wall design has been found in which the ratio of the static to the dynamic stiffness can be in excess of 1000:1 and where the stiffness changes from the static to the dynamic value in such a way that the acoustical behavior is nearly that of a perfectly limp wall. If desired, the loss tangent of the wall can be made large and nearly constant over a wide range of frequencies.
Auditory Perception of Temporal Order
Authors: Hirsh Ira J.
Published: September 2005

Whereas temporal intervals as short as a few milliseconds are sufficient to separate two brief sounds so that a listener will report that there are two (instead of only one) sounds, a longer separation time of between 15 and 20 msec is required for the listener to report correctly which of the two sounds preceded the other. This minimum temporal interval appears to be independent of the kinds of sounds used: whether short or long, of high or low frequency, of narrow or wide band width. There is some suggestion that rise-time and duration may change this minimum interval, but these somewhat secondary relations are not investigated in detail here. The length of the required temporal interval suggests that the judgment of order requires other mechanisms than those associated with the peripheral auditory system.
Loudness of Complex Sounds as a Function of the Number of Components
Authors: Scharf Bertram
Published: September 2005

The loudness of complex sounds was studied as a function of the number of components. Complexes of two, three, four, and eight tones, and a band of white noise were matched in loudness to a 1500-cy tone. The over-all spacing, ΔF, between the lowest and highest components of these stimuli was held constant at either 175, 1600, or 3400 cps. All the complexes were centered around 1500 cps when ΔF was either 175 or 1600 cps. At each of the four levels tested (25, 50, 75, and 90 db SPL), loudness remained essentially unchanged when only the number of components within a complex was varied. This invariance of loudness occurs even though inhibition may be greater within the complexes that contain a larger number of components. It is suggested that the increased inhibition may be offset by greater loudness summation when the energy is more evenly distributed within the complexes.
Tonotopic Organization of the Cat Auditory Cortex for Some Complex Stimuli
Authors: Kiang N. Y-S. , Goldstein M. H.
Published: September 2005

There is psychophysical evidence that both spectrum and periodicity of acoustic signals may be cues for pitch judgments. At the level of the auditory nerve, these stimulus characteristics seem to be coded in terms of place and time pattern. Very little is known of their representation higher levels of the nervous system. Tonotopic organization of the auditory cortex has been demonstrated in anesthetized cats by the evoked strychnine potential technique. In these demonstrations only tonal stimuli were used. We use similar physiological preparations but employ acoustic stimuli that permit independent manipulation of spectrum and periodicity. The results show that the previously reported tonotopic organization is based only upon spectral characteristics of the stimulus.
Evaluation of a Modulated Air-Flow Loudspeaker
Authors: Webster John C. , Klumpp Roy G. , Witchey Albert L.
Published: September 2005

As part of an over-all evaluation of the USNEL Flight Deck Communications System, an RCA modulated air-flow loudspeaker (air speaker) was tried out as a speech and alarm signaling transducer on the flight deck of an aircraft carrier. Tests with 200- to 6000-cps noise showed that the air speaker produced 130 db SPL at optimum points on the deck, as compared to 110 db for the present system. Speech intelligibility and alarm detection tests showed the air speaker to be usable with jet aircraft at idle (30%) power while the present loudspeakers could not be heard. Neither loudspeaker system was adequate with jets at full power.
Auditory Adaptation in Noise
Authors: Wright H. N.
Published: September 2005

The initial rate, extent, and recovery from auditory adaptation were measured in both the presence and absence of noise in ten normal ears by the method of fixed intensity at 250, 1000, and 4000 cps. It was found that the initial rate and extent of adaptation to a tone in noise were greater than to the tone alone at 4000 cps, but not at either 250 or 1000 cps. Recovery from adaptation to tones in both noise and quiet was found to be equivalent, but never complete, at each frequency. When the noise was sustained in one ear and a tone introduced over the noise at 1-min intervals, there was a systematic decline in response at 250 and 1000 cps, but not at 4000 cps. When the noise was not sustained, but followed the same periodic intervals as the tone, there was a decline in response at 4000 cps, but not at either 250 or 1000 cps.
On Indices of Signal and Response Discriminability
Authors: Pollack Irwin
Published: September 2005

Two indices of a listener's performance in a combination system are distinguished. One reflects the discriminability among the items of the message source—the index of signal discriminability. One reflects the discriminability by a listener among his own responses—the index of response discriminability.
Acoustics of Severance Hall
Authors: Shankland Robert S. , Flynn Edward A.
Published: September 2005

During 1958 a number of corrections were made in the acoustics of Severance Hall designed to lengthen the reverberation time, especially at the higher frequencies, and to project more sound energy from the orchestra to the audience. An entirely new stage shell has been constructed of heavy wood and is tightly enclosed so that a large fraction of the orchestral sound is now directed to the audience. In addition, the shape of the stage shell provides a considerable amount of mixing and blending of the sound, which is a great advantage for the conductor and orchestra. This feature will also be important for the numerous recordings made by the Cleveland Orchestra. The material and design of the heavy wood shell, floor, and risers for the stage, were chosen to achieve a large measure of reflection without undue resonance. Another important modification is the simplification of the proscenium and removal of the heavy curtain which in effect brings the orchestra out into the auditorium to a greater degree than before. Finally, the heavy lined carpeting which was present throughout Severance Hall on all aisles, promenades, and under the seats, has been removed and replaced with an attractive vinyl tile covering of low acoustical absorption. These modifications have made a notable improvement in the quality and intensity of orchestral music in Severance Hall and are highly approved by the concert audience. [R. S. Shankland, J. Acoust. Soc. Am. 31, 121 (A) (1959)].
Transmission Loss of Some Masonry Walls
Authors: Watters B. G.
Published: September 2005

The transmission loss of very large, single, solid walls is given by the “coincidence-effect” theory as presented by L. Cremer and others. The results of this theory have been compared with data from field measurements on some typical, masonry walls and are found to be in fairy good agreement. The differences which exist are believed to reflect the inapplicability of the theory to finite sized walls and the imperfection of the sound diffusion in the test rooms. An empirical design technique is presented which agrees more closely with typical field results.

The hollow masonry block walls which were studied behave much like solid walls with the same surface weight and bending stiffness. Laboratory techniques are described for measuring the physical constants of these and other materials.

Tests made on a typical lightweight aggregate masonry block show that the porosity through the block faces does not greatly reduce the transmission loss. However, painting such a block may increase the bending stiffness of the wall and slightly alter the transmission loss.
Sabine Reverberation Equation and Sound Power Calculations
Authors: Young Robert W.
Published: September 2005

Formulas pertaining to the calculation of noise in a room produced by a steady source, the measurement of sound power in a reverberant room, and the calculation of reverberation time are reviewed for their appropriateness to engineering use. It is recalled that the simple Sabine reverberation equation can be used without loss of generality provided one associates with a given sound absorbing material a coefficient which is the negative natural logarithm of the energy reflection coefficient; the name Sabine coefficient is tentatively suggested for this quantity. It is noted further that the coefficient usually obtained from tests in a reverberation room is the Sabine coefficient and not truly the sound energy absorption coefficient. A relation is given, between average sound pressure in a room and the power delivered by a source, that does not require averaging absorption coefficients and which is only slightly dependent upon the mean free path. The “Sabine absorption” Sā is more nearly correct (and easier to compute) than the room constant, Sᾱ/(1 −ᾱ) both for the sound-pressure-power relationship and reverberation time calculation, where S is the wall area, ā the average Sabine coefficient, and ᾱ is the average energy absorption coefficient. For sound power level calculations appropriate graphs are provided, showing dependence of intrinsic acoustic impedance and bulk modulus on temperature and barometric pressure or salinity, for air and water, respectively.
Variation of Acoustic Velocity with Temperature in Aqueous Solutions of Certain Inorganic Sulfates
Authors: Marks Graham W.
Published: September 2005

Much can be learned about the molecular properties of liquids and solutions from investigations concerning acoustic velocity and attenuation. However, systematic studies are needed. Sound velocities in aqueous solutions of Li2SO4, Na2SO4, KHSO4, K2SO4, (NH4)2SO4, and MgSO4 were measured over wide ranges of concentration and over the temperature range 0 to 80°C. It was found that the sound velocity versus temperature curves rise and are displaced toward lower temperatures with increase in concentration. Except at concentrations above about one molar the curves are, within the limits of experimental error, the same as the displaced curve for water. The specific acoustic impedance of these sulfate solutions varies linearly with concentration at 20°C. Adiabatic compressibilities are well represented by an empirical expression. Relative association was found to rise with increase in concentration. This is because of solvation of the ions in solution. From the available data apparent molal compressibilities were computed for the temperature range 15 to 35°C.
Isolation from Mechanical Shock with One- and Two-Stage Mounting Systems
Authors: Snowdon J. C. , Parfitt G. G.
Published: September 2005

The damaging potential of mechanical shock experienced by resiliently mounted equipment is discussed in general terms. It is pointed out that the displacement, relative displacement, and acceleration of the mounted item, expressed as nondimensional quantities, describe the likelihood of damage in particular circumstances.

The performance of mounting systems has been judged by their response to a step-like shock displacement. The nondimensional quantities above have been determined as functions of the steepness of the leading edge of the step displacement for one- and two-stage, linear, viscously damped spring mountings. Heavy damping is beneficial in a mount in several respects, and its adverse effects on transmitted acceleration can be mitigated by the use of the two-stage mountings.
Semantic Reactions to Systematically Varied Sounds
Authors: Solomon Lawrence N.
Published: September 2005

Noise bands simulating passive sonar sounds were varied in terms of spectrum (band passed from 150–600 cps, or 600–2400 cps, or 2400–9600 cps); in terms of amplitude modulation (simulated screw beats) at beat rates of 0, 3, 5, or 11 per second; and in terms of presence or absence of accent within a group of 4 beats. Every combination of these parameters (21 in all, not 24, since at zero beat rate there can be no accent) was rated by 20 subjects in terms of their aurally perceived characteristics on 15 scales representing seven different dimensions.

Analysis was made of the manner in which the 21 sounds clustered within the space defined by the seven psychological dimensions. Two major clusters of sounds were observed, differentiated primarily on the basis of band pass condition (high frequency vs low frequency). Exceptions to this general rule were analyzed to reveal the interactions between band pass condition, beat rate, and accent.
Method of Improving Acoustic Transmission in Folded Horns
Authors: Carlisle Richard W.
Published: September 2005

A novel principle has been developed, applicable to folded horns, for improving the acoustic transmission around bends having a radius greater than one-quarter wavelength. This consists of the use of a conoidal reflecting type surface in the outer half of the fold. It is beneficial in the frequency-special region between the usual horn wave expansion action and transmission by specular or optical type reflection. A practical application is described.
First Motion Methods in Theoretical Seismology
Authors: Knopoff Leon , Gilbert Freeman
Published: September 2005

Techniques are presented for approximating integral solutions to some problems in theoretical seismology. The approximations obtained are the first terms of asymptotic series in powers of t−t0, where t is the time and t0 is an arrival time. The approximations are obtained by evaluating the integral form of the Laplace transform of the time solution by the saddle point method or a variation of it. To the resulting expression is applied a Tauberian limit theorem from which is obtained the time solution. Two examples are given which illustrate some of the specific techniques for the use of the method.
Attenuation and Regeneration of Sound in Ducts and Jet Diffusers
Authors: Ingard Uno
Published: September 2005

The effect of noise regeneration by fluid flow on the performance of noise-attenuating structures is examined with special attention to muffler design. The insertion loss of a single element, as well as a continuous distribution of attenuating and noise-regenerating elements, is studied. For example, in a duct with an attenuation constant β per unit length and a regeneration r per unit length, the upper limit of the insertion loss is 10 log (2Eβ/r), where E is the source strength. It should be noted that the insertion loss of a noise-regenerating attenuator depends on the sound level to be reduced.

An analysis of experimental data on jet noise indicates that the power spectrum of a circular jet depends on frequency, f, and Mach number, M, approximately as f2M5 at low frequencies, as f−2.5M9.5 at high frequencies, and as M7 at the peak frequency. In terms of the corresponding jet spectrum, for which an empirical analytical expression is given, the maximum attainable insertion loss of a jet muffler diffuser is presented as a function of frequency. The deviation of the characteristics of a “lossy” diffuser from this upper limit depends on the attenuation and regeneration characteristics of the acoustical elements in the muffler. These characteristics are investigated for the special element consisting of a perforated sheet, and the results are applied to an analysis of the insertion loss of a muffler diffuser of the perforated basket type.