摘要:

Loudness scales for 1‐kHz tones, as determined by conventional scaling procedures, have yielded conventional loudness functions which grow as approximately the 0.50 power of the sound pressure. That is, a 10‐dB increase in intensity corresponds roughly to a doubling of loudness. By plotting the loudness as a unidimensional logarithmic function of intensity, we imply that ifAis twice as loud asB, which, in turn, is twice as loud asC, thenAis four times as loud asC. In order to test this prediction loudness ratio estimates were obtained from 10 subjects on four 7×7 matrices of stimuli at 1 kHz with differing interstimulus spacings (30–90 dB SL in 10‐dB steps; 40–70 dB SL in 5‐dB steps; 40–55 dB SL in 2.5‐dB steps; and 30–90 dB SL in irregular intervals). Using a multidimensional representation of the data based upon Shepard's analysis of proximities [R. N. Shepard, Psychometrika27, 125–140, 210–246 (1962)], a simple two‐dimensional configuration was found which adequately represented the data. If the diagram is projected on only one dimension, an approximation is obtained that is locally accurate, i.e., the loudness‐ratio data are accurately represented over a limited range.

ISSN:0001-4966    

DOI:10.1121/1.1975967

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

摘要:

This problem is a natural continuation of the works of Morse on the rigid piston in a rigid spherical housing. Its solution is made possible by the little known but widely applicable method of Botman. A free circular disk driven at its center is assumed as the dynamic model. The method of Kirchhoff as given by Rayleigh is used to find the values ofkafor the first two axisymmetric modes. These together with the rigid piston mode give an adequate representation for the range ofkaof interest (ka<8). Botman's method is used in conjunction with an IBM 7090 computer. Machine limitations dictated the use of only 10 spherical harmonics: close fits to vibrational modes were not possible in spite of the choice of θ = 30° for the angle subtended by the piston. No significant error in the integrated radiation reaction is expected, however,owing to the cutoff properties of spherical wave impedances. Computed graphs ofX,R, directivity, and source level with comparison to Morse's results are given. Computed patterns are also shown. Some inferences with regard to the design of practical underwater radiators characterized by wide frequency range and omnidirectional patterns are made.

ISSN:0001-4966    

DOI:10.1121/1.1975971

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

摘要:

A method is presented for the numerical study of the interaction of elastic bodies and acoustic fields. It is based on an integral equation technique wherein a sheet of acoustic sources and a sheet of forces are spread over the body surface. Their strengths are adjusted so that the boundary conditions are satisfied at the fluid‐solid interface. Because the calculation involves only a description of the body surface, it offers a more rapid numerical process than the more usual finite element calculations, where equations of motion must be developed for all points within the interior of the body as well.

ISSN:0001-4966    

DOI:10.1121/1.1975979

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

摘要:

Concepts of sonic boom pressure loading of building structures and the associated responses are reviewed and results of pertinent theoretical and experimental research programs are summarized. The significance of sonic boom load time histories, including waveshape effects, are illustrated with the aid of simple structural elements such as beams and plates. Also included are discussions of the significance of other such phenomena as three‐dimensional loading effects, air cavity coupling, multimodal responses, and structural nonlinearities. Measured deflection, acceleration, and strain data, from laboratory models and full‐scale building tests are summarized, and these data are compared where possible with predicted values. Damage complaint and claim experience due both to controlled and uncontrolled supersonic flights over communities are summarized with particular reference to residential, commercial, and historic buildings. Sonic boom induced building responses are compared with those from other impulsive loadings due to natural and cultural events and from laboratory simulation tests.

ISSN:0001-4966    

DOI:10.1121/1.1975991

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

摘要:

Two areas of capitation research have met with limited success until recently: (1) the measurement of the strength or cavitation threshold of pure (mote‐free) liquids; and (2) the prediction of the threshold of liquids known to be “impure.” Advances in these areas are reviewed and new results are reported. The influence of mote size and mote wetability on the cavitation threshold has been studied theoretically [R. Apfel, J. Acoust. Soc. Amer. (to be published)]. Results of this work bring some semblance of order to a wide variety of cavitation observations. By minimizing the number of motes in the liquid sample and by isolating the sample from solid container surfaces, it is possible to measure the strength of pure liquids. This has been accomplished by testing small filtered droplets of the sample suspended in an “inert” host liquid. Furthermore, the tests have been performed at temperatures at which the sample has undergone significant super heating; under this condition, the predicted tensile stresses are low enough to be accessible experimentally. This technique [R. Apfel, J. Acoust. Soc. Amer. (to be published)]has been modified with the intention of studying the liquid‐to‐solid phase transition. [Work supported by the Office of Naval Research.]

ISSN:0001-4966    

DOI:10.1121/1.1976005

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

摘要:

The laboratory evaluation of the acoustic microbubble spectrum analyzer has disclosed several types of persisting microbubble phenomena as a varying abnormal attenuation with frequency. Microbubble populations are detected in a tank filled with tap water only sporadically and may be influenced significantly by barometric pressure. Distilled water open to the atmosphere can become rapidly charged with persisting microbubbles. An increase of temperature or a reduction of local pressure can be used to expand microbubbles into the detection range of the instrument. For limited excursions of temperature and pressure, the change in attenuation is reversible, indicating a stability range for persisting microbubbles. The observed attenuation spectra include examples of sharp peaks, which indicate a narrow range of microbubble size, and broad peaks, which indicate a distribution of sizes. [This work supported in part by the Office of Naval Research.]

ISSN:0001-4966    

DOI:10.1121/1.1976009

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

摘要:

These experiments explored the empirical relations among growth of detection as a function of SPL, amplitude discrimination performance, and temporal integration. To a first order of approximation the results were as follows: ROC curves in quiet were linear on normal‐normal coordinates, the slope of the psychometric function did not vary as a function of duration, the slope of the psychometric function was inversely proportional to the size of the difference limen, and amount of temporal integration was inversely related to the slope of the psychometric function. Some theoretical considerations relating to this last finding will be discussed.

ISSN:0001-4966    

DOI:10.1121/1.1976025

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

摘要:

The threshold of a harmonically related pure‐tone maskee (Me) varies sinusoidally as its phase is shifted relative to a sufficiently intense masker (Mr) when both are simultaneously presented to one ear. This phenomenon can be explained by either of two approaches. One involves the assumptions that (a) there is a summation between waveforms within the cochlea and (b) the threshold measurements are consequences of peak detection. To test this interpretation, six normal listeners traced their thresholds at 1500, 2000, and 2500 Hz in the presence of a 1000‐HzMrat each of five intensities, 50–90 dB (SPL) at 10‐dB intervals. Within each session, the phase was shifted in randomly ordered 60° steps through one complete period (of theMe). When confusions due to a 500‐Hz difference tone are avoided by using a narrow‐band (270–540 Hz) masking noise, no phase effects at 1500 and 2500 Hz are evident. The thresholds for the 2000‐HzMe, however, show the usual phase dependencies at equalMrlevels. These findings are inconsistent with the two‐tone interaction explanation and thus support the interpretation that emphasizes a nonlinear response of the auditory system and direct interference between aural and acoustic harmonics.

ISSN:0001-4966    

DOI:10.1121/1.1976029

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

摘要:

The problem of whipping of an eccentric, long circular shaft under linearly varying tension rotating in a fluid medium is investigated within linear theory. In view of the great lengths under consideration, the bending stiffness is assumed negligible. Internal damping is neglected and the external damping is assumed viscous. The mass eccentricity is assumed to be a deterministic function of the axial coordinate. Only steady‐state conditions are considered. The deflection of the shaft is obtained by finite Hankel transforms, and the bending stresses are subsequently determined approximately from the curvature of the deflection curve. Numerical results are given in graphical form for a shaft with a pulse‐type eccentricity function in one plane for several values of speed of rotation and tension at the lower end.

ISSN:0001-4966    

DOI:10.1121/1.1976037

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

摘要:

The preceding paper utilizes an “equivalent system” approach to evaluate the response level‐crossing statistics of complex linear systems subjected to impulsive noise excitation. In the past, attention has been directed toward situations where either the impulse‐noise‐density parameter γ is small, say less than unity, or very large, say greater than 10. In the former it was necessary to include only the effect of the most recently occurring impulse, while the latter could be modeled with Gaussian statistics amenable to theoretical analysis. In this work, the analysis is extended to intermediate values of γ by including the effects of all of the preceding impulses in an approximate way. New analytical expressions are derived for the response level crossings. Empirical level‐crossing data from a single‐degree‐of‐freedom system is presented that shows this new approach to be promising with the theoretical results providing an upper bound on the data. Empirical studies on systems with several degrees of freedom also show the power‐weight method “equivalent system” approach developed for γ<1 to be valid for values of γ as large as 10. Thus, one can now utilize dynamic characterization to analyze conveniently the level‐crossing problem for a wide class of impulsive noise problems. [Work supported by grant from the National Science Foundation.]

ISSN:0001-4966    

DOI:10.1121/1.1976057

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP