摘要:

The absorption of sound has been measured inCO2,CS2,C2H4O, and in mixtures of the latter two gases withCO2for frequencies ranging from 2 to 10 kc and for pressures ranging from 3 to 300 mm of Hg. The tube method was employed. The absorption was determined by observing the decrease in sound pressure as the path length between the speaker and the microphone was increased. A fixed condensor microphone and a movable ribbon‐type speaker were used.The measured absorption coefficient was corrected for the effect of the tube and also for the absorption due to viscosity and heat conduction of the gas. The corrected absorption coefficient was then plotted as the attenuation coefficient per wavelength against the logarithm of the ratio of frequency over pressure. These curves were then compared to those determined from Bourgin's Theory for mixtures of absorbing gases. The agreement between the observed attenuation and that predicted by the theory was within 5 percent.

ISSN:0001-4966    

DOI:10.1121/1.1907245

出版商:Acoustical Society of America    

年代:1953

数据来源: AIP

摘要:

Steady rotational flow is known to occur in the vicinity of a smooth rigid object oscillating to and fro in a viscous incompressible fluid. For a small oscillation amplitude the steady flow is shown theoretically to be invariant to the coordinate transformation which renders the object stationary.

ISSN:0001-4966    

DOI:10.1121/1.1907246

出版商:Acoustical Society of America    

年代:1953

数据来源: AIP

摘要:

A new technique for the measurement of sound velocity in liquids has been developed, which is especially suited to frequencies in the range from 0.5 to 5 mc. It employs an approximation to the boundary conditions in Guptill's closed form solution for the radiation field between two infinite walls with a piston source in one wall.Measurements have been made in distilled water at 0.6 and 7.6 mc with an error of less than 0.2 percent in the low‐frequency measurements. No dispersion is indicated to the order of the experimental error, in the temperature range from 10 to 20°C.A description of the apparatus is given.

ISSN:0001-4966    

DOI:10.1121/1.1907247

出版商:Acoustical Society of America    

年代:1953

数据来源: AIP

摘要:

The cavitation threshold of water supersaturated with air at hydrostatic pressure is utilized as a pressure reference level against which the output of a transducer may be referred. The threshold may be determined within 0.2 decibel in a purely radial standing‐wave field. A simple system is described for performing the measurements.

ISSN:0001-4966    

DOI:10.1121/1.1907248

出版商:Acoustical Society of America    

年代:1953

数据来源: AIP

摘要:

The electronic sound absorber is so named because it absorbs sound or reduces the sound level by means of an electronic transducing system, as contrasted to conventional sound absorption by direct conversion from acoustical to heat energy. The electronic sound absorber consists of a microphone, amplifier, and loudspeaker connected so that, for an incident sound, wave and sound pressure at the microphone is reduced. Thus it will be seen that the electronic sound absorber is a feedback system which operates to reduce the sound pressure in the vicinity of the microphone. The sound pressure in the neighborhood of the microphone can be reduced 10 to 25 decibels over a frequency range of three octaves in the low‐frequency portion of the audio‐range. The electronic sound absorber may be used to reduce the noise over a small volume, that is, spot type noise reducer or it may be used with an acoustical resistance to obtain a high order of sound absorption in the low‐frequency range.

ISSN:0001-4966    

DOI:10.1121/1.1907249

出版商:Acoustical Society of America    

年代:1953

数据来源: AIP

摘要:

Relations for an electromechanical network that contains both electrostatic and electromagnetic coupling and has the antireciprocal transfer characteristic described by McMillan are developed. The effect of hysteresis and eddy currents is included. An equivalent electrical circuit that makes use of the “ideal gyrator” to give the antireciprocal characteristics presented. Several sets of experimental measurements are described which clearly show the nonreciprocal characteristics of the system.

ISSN:0001-4966    

DOI:10.1121/1.1907250

出版商:Acoustical Society of America    

年代:1953

数据来源: AIP

摘要:

Three distortion methods, the harmonic, the SMPE intermodulation, and the CCIF (a difference frequency), have been studied, mainly on a theoretical basis, as a means of analyzing distortion encountered in phonograph reproduction. The harmonic method is somewhat difficult to apply and some of the harmonics may be beyond the range of the system. The IM has been used in the past with considerable success, and appears to be a good method of analyzing tracing distortion. The difference frequency methods appears to be somewhat insensitive to tracing distortion but offers theoretical advantages in that the analysis may be made right up to the cut‐off frequency of the system, practically it is somewhat difficult to apply.

ISSN:0001-4966    

DOI:10.1121/1.1907251

出版商:Acoustical Society of America    

年代:1953

数据来源: AIP

摘要:

The electro‐optic effect in the crystal ammonium dihydrogen phosphate provides a high‐speed light valve with ruggedness, long life, and ease of handling not possessed by the similar Kerr effect in liquids. In this paper the design of a practical sound reproduction unit for making variable density 35‐mm tracks will be described. Frequency response of the light valve is flat to over 20 000 cycles, the over‐all system being limited to about 10 000 by the slit‐width film speed effect. Tests of distortion and sound quality in the sound tracks obtained are described.

ISSN:0001-4966    

DOI:10.1121/1.1907252

出版商:Acoustical Society of America    

年代:1953

数据来源: AIP

摘要:

Experimental data are submitted indicating the existence of a direct action of ultrasonic waves on a photographic emulsion, contrary to the views of some other workers. All of the evidence obtained here indicates a closer correlation with the softness of the emulsion than with the known behavior of ultrasonically produced luminescence. Information is presented as to temperature dependence of the image, effect of ambient pressure, light shielding, and the behavior of various types of commercial emulsions.

ISSN:0001-4966    

DOI:10.1121/1.1907253

出版商:Acoustical Society of America    

年代:1953

数据来源: AIP

摘要:

An acoustic lens combined with a conical horn can be used to obtain a highly directional microphone without some of the disadvantages of the parabolic microphone. The directional characteristics can be calculated satisfactorily if one assumes that the horn provides uniform flooding of the lens aperture.

ISSN:0001-4966    

DOI:10.1121/1.1907254

出版商:Acoustical Society of America    

年代:1953

数据来源: AIP