摘要:

The correct reproduction of “perceived reverberation” serves as quality criterion about electroacoustic transmission systems. By the use of such transmission systems, quality judgments in architectural acoustics may be made without differences between sound sources influencing these judgments.

ISSN:0001-4966    

DOI:10.1121/1.1912858

出版商:Acoustical Society of America    

年代:1972

数据来源: AIP

摘要:

In electrodynamic microphones there are two major sources of thermal agitation noise, namely, the electromotive force due to the thermal agitation of the electrons in the conductor and the electromotive force produced by the motion of the diaphragm due to the thermal agitation of the molecules impinging upon the diaphragm. In commercial microphones, the thermal acoustic noise is far below the thermal electric noise. Therefore, in order to detect the thermal‐acoustic noise, a special high‐sensitivity ribbon velocity microphone was designed and built. The presence of the thermal acoustic noise was detected and measured in the microphone. The theoretical and experimental data correspond for both the thermal electric noise and the thermal acoustic noise.

ISSN:0001-4966    

DOI:10.1121/1.1912859

出版商:Acoustical Society of America    

年代:1972

数据来源: AIP

摘要:

The basic theory of a large space bandwidth signal analysis by means of a two‐dimensional optical processor is discussed and the synthesis of a near real‐time optical sound spectrograph is presented. In the current state‐of‐the‐art, the realization of an optical sound spectrograph is feasible. It is also concluded that the optical sound spectrograph may offer a broader frequency range of analysis and flexibility in spectrum data handling. The former may be important in ultrasonic signal analysis; the latter may be important in future research in automatic speech recognition, synthesis, and translation.

ISSN:0001-4966    

DOI:10.1121/1.1912860

出版商:Acoustical Society of America    

年代:1972

数据来源: AIP

摘要:

Sound rays are traced numerically from a point source on the axis of a jet flow with realistically chosen velocity profiles. The directivity patterns computed from the ray paths have no cone of absolute silence, in contrast with analytic results for nonspreading jets. A related observation is that the surfaces of constant phase are ultimately spherical. Nevertheless, the computed axial refraction valleys are much deeper than those observed in jet noise studies. The difference is due to diffraction, which tends to offset refraction effects at all but the highest (ray‐acoustic) frequencies.

ISSN:0001-4966    

DOI:10.1121/1.1912861

出版商:Acoustical Society of America    

年代:1972

数据来源: AIP

摘要:

The equations appropriate to the propagation of sound in a realistic jet flow have been solved by finite‐difference methods for the case of a sinusoidal point source on the axis of a subsonic jet. Each numerical solution provides detailed phase and amplitude information throughout the sound field. At the high‐frequency limit the finite‐difference results agree with ray‐tracing results. Also, the computed farfield directivity patterns generally agree with available experimental data and lend further support to the view that the downstream “valley” in jet noise is due to refraction rather than to the inherent directivity of the sound generated within the region of turbulence. Unexpected findings are that the flow beyond 100 nozzle diameters continues to deepen the refraction valley significantly, and that the sound‐pressure level reduction at a fixed point on the axis at first increases as the source is moved downstream from the nozzle. For the application of the refraction results to the computation of jet noise directivity, is found that the distortion of the constant phase surfaces can be neglected except at high frequencies.

ISSN:0001-4966    

DOI:10.1121/1.1912862

出版商:Acoustical Society of America    

年代:1972

数据来源: AIP

摘要:

A series of informal measurements of the mechanical driving‐point impedance properties of a toy xylophone and a souvenir steel drum is described. Complicating factors are indicated. It is shown that interesting mechanical properties of the toy xylophone can readily be demonstrated. In contrast, it is more difficult to perform accurate measurements upon the steel drum, and the measurements program was ultimately directed toward the properties of a large steel drum, with greatly improved accuracy.

ISSN:0001-4966    

DOI:10.1121/1.1912863

出版商:Acoustical Society of America    

年代:1972

数据来源: AIP

ISSN:0001-4966    

DOI:10.1121/1.1912864

出版商:Acoustical Society of America    

年代:1972

数据来源: AIP

ISSN:0001-4966    

DOI:10.1121/1.1912866

出版商:Acoustical Society of America    

年代:1972

数据来源: AIP