摘要:

A method is presented for replacing the Lagrangian boundary condition which occurs in the analysis of finite‐amplitude radiation from vibrating pistons by an approximately equivalent condition which permits the analysis to be carried out in Eulerian form.

ISSN:0001-4966    

DOI:10.1121/1.1909159

出版商:Acoustical Society of America    

年代:1962

数据来源: AIP

摘要:

The distribution of crests associated with a lightly coupled bimodal vibrating system under band‐limited white‐noise excitation has been calculated and measured. Measured crests of the strain response of a mass‐loaded cantilever beam, used as the bimodal system, follow the expected Rayleigh distribution to within experimental accuracy. Noteworthy is the result that crests of four times the rms strain are obtained using a bimodal configuration, and crests of five times the rms strain are obtained when the beam is vibrating in a unimodal configuration.

ISSN:0001-4966    

DOI:10.1121/1.1909160

出版商:Acoustical Society of America    

年代:1962

数据来源: AIP

摘要:

In a recent paper Hunt examined the relation between strain and velocity in forced resonant motion for a wide variety of elastic bodies. He found that the maximum strain was always proportional to the ratio of the maximum vibratory velocity to the velocity of sound in the body and that the constant of proportionality appeared to be constrained to remain in a narrow range extending about an order of magnitude. Similar results were obtained independently by Ungar [see E. E. Ungar, “Maximum Stresses in Beams and Plates Vibrating at Resonance,” J. Eng. Ind. Trans. ASME84B, 149–155 (1962)] for uniform beams and plates. In this note a similitude argument is used to establish the form of these results. It is also pointed out that because of both strain and velocity concentrations the range of possible values for the proportionality constant can be very much wider than the range found by Hunt.

ISSN:0001-4966    

DOI:10.1121/1.1909161

出版商:Acoustical Society of America    

年代:1962

数据来源: AIP

摘要:

A sensitive aural method for detecting the onset of cavitation developed by a resonant high‐frequency transducer and a method of determining the velocity of the cavitation bursts are discussed.

ISSN:0001-4966    

DOI:10.1121/1.1909162

出版商:Acoustical Society of America    

年代:1962

数据来源: AIP

摘要:

A simple method for the prediction of the stiffness‐controlled voltage response of a hydrophone configured for deep‐sea operation is described. The approach utilizes previous work in this area, enlarged to include the effects of various degrees of decoupling of the acoustic field from the back face of the hydrophone. Two configurations of importance, the spherical and the cylindrical, have been analyzed, and the results presented graphically. For both cases, the equations of equilibrium and the equation of compatibility are solved and evaluated by the use of boundary conditions. These stress equations, thus generated, and the electromechanical constants are then related to yield the voltage/pressure sensitivity equations. The graphs show the effects of thickness to diameter, comparison of the air‐backed to the pressure‐equalized hydrophone, and the various degrees of decoupling of the acoustic field from the back face of the hydrophone. For all cases, both barium titanate and lead zirconate titanate are considered.

ISSN:0001-4966    

DOI:10.1121/1.1936955

出版商:Acoustical Society of America    

年代:1962

数据来源: AIP

摘要:

The directivity pattern and source level of a large, cylindrical transducer were computed by using Kirchhoff's formula with a simple approximation for the normal pressure gradient. The integration was performed numerically over a finite cylinder. Near‐field pressure amplitude and phase measurements were made over the surface of integration by rotating the transducer and measuring the output of a line hydrophone less than 1 wavelength from the active face. The measurements were made on the leading edge of the received pulses—before steady‐state conditions were reached. This was done to simulate this transducer operating in a tank of diameter only about twice that of the transducer. Under such conditions, interference due to tank‐wall reflections would begin when the amplitude of the pulse envelope was as much as 2–3 dB below the steady‐state level. Computed directivity patterns agreed well with equivalent measured ones, but, naturally, computed source levels were 2–3 dB low. A correction term was derived from the first portion of the pulse risetime curves, and was applied to the source‐level values to give good agreement with measured ones. The present results indicate that accurate transducer calibration can be obtained in reflective tanks considerably smaller than those used in previous work.

ISSN:0001-4966    

DOI:10.1121/1.1936959

出版商:Acoustical Society of America    

年代:1962

数据来源: AIP

摘要:

The masking produced by 2 continuous sinusoids located equidistant in frequency from the signal, a pulsed sinusoid of110 sec, was studied. The 2 sinusoidal maskers were of equal energy. Their separation in frequency Δfwas varied. The main parameter of the experiment was the frequency of the pulsed signal. The results can conveniently be summarized in one graph. Along the abscissa, we plot the frequency separation of the maskers (Δf). Along the ordinate, we plot the intensity of the pulsed signal (Is) needed for some constant level of detectability. As the frequency separation of the maskers increases, the curve descends, indicating the pulsed tone is becoming easier to hear (Is∝1/Δf). For moderate frequency separations (Δf<100 cps), the results are independent of center frequency. For example, essentially the same signal intensity in SPL is needed at 250, 1000, or 4000 cps to overcome the masking produced by 2 continuous tones when these maskers are located 20 cps above and below the frequency of the signal. At much wider frequency separations, the results are dependent on center frequency, and a critical band of a kind may be measured. The width of the “critical band” inferred from this experiment is about the same size as the half‐response points of the curve relating the amplitude of the traveling‐wave envelope to frequency; i.e., the “critical band” is nearly 600 cps wide at 1000 cps. [This work was supported in part by the U. S. Army Signal Corps, the U. S. Air Force ESD Contract AF19(604)‐7459, the Office of Naval Research, and in part by the National Science Foundation (Grant G‐21807).]

ISSN:0001-4966    

DOI:10.1121/1.1936963

出版商:Acoustical Society of America    

年代:1962

数据来源: AIP

摘要:

The attenuation of acoustic energy in the ocean at a frequency of 40 kc was measured by means of a bottom‐mounted array of 7 hydrophones in 1800 ft of water. The source of short pulses was a ship‐mounted projector. Measurements were made by determining the peak amplitude of the received pulses as a function of range. Spherical transducers were used to minimize the effect of patterns on the measurements. These measurements agreed with the unpublished values obtained by APL, Washington. In addition, the ambient sea noise as a function of sea state was measured. The values obtained, when corrected for the attenuation over the depth of 1800 ft, agree with published values within12 dBfrom sea state 3 down to below sea state 1, where system noise became predominant.

ISSN:0001-4966    

DOI:10.1121/1.1936973

出版商:Acoustical Society of America    

年代:1962

数据来源: AIP

摘要:

The highly reverberant “music acoustics” design for Philharmonic Hall, Lincoln Center, New York, necessitated a carefully engineered speech‐reinforcement system to assure satisfactory intelligibility for speech events. Two alternate and competitive “central” loudspeaker systems, having similar directional characteristics, were recommended, one employing direct‐expansion radial high‐frequency horns, and the other employing multicellular high‐frequency horns. Also, alternate constructions were allowed for the low‐frequency horns, the choice depending upon the visual requirements of the architect. The sound‐reflecting panels in the hall interfere somewhat with the performance of the sound system at low frequencies. However, the system has met its design goals. Frequency‐response and word‐articulation tests are presented.

ISSN:0001-4966    

DOI:10.1121/1.1936977

出版商:Acoustical Society of America    

年代:1962

数据来源: AIP

摘要:

Representative computations of the response to sinusoidal vibration of coupled systems composed of damped beams and lumped elements of mass are described. The beams vibrate in their transverse modes, and are excited only at their midpoints. They are assumed to possess damping of the solid type. Discussed in detail is the response to vibration of a simply clamped beam excited at points other than its center.

ISSN:0001-4966    

DOI:10.1121/1.1936982

出版商:Acoustical Society of America    

年代:1962

数据来源: AIP