摘要:

Several features of the gross and microscopic anatomy of the ear will be discussed and illustrated, particularly some features that frequently enter into mathematical and physical theories of the action of the ear. Anatomical dissections and microscopic preparations will be on exhibition after the presentation.

ISSN:0001-4966    

DOI:10.1121/1.1917150

出版商:Acoustical Society of America    

年代:1950

数据来源: AIP

摘要:

New materials and techniques have made possible the design of useful electrostatic loudspeakers. High polarizing and signal potentials across air gaps which are large enough to permit diaphragm excursions of a magnitude necessary for the production of low frequencies, together with an acoustically transparent stationary electrode and a diaphragm which is light compared with the mass of the entrained air, result in unusually good pressure response and phase response characteristics as well as a useful amount of power from relatively small areas. The only resonances are those which arise between the compliance of the diaphragm material and the mass of the entrained air, and these can be made to occur below the useful range of audiofrequencies. The active radiating area is made to retract with frequency to preserve good polar response and to improve the impedance characteristic, by making the distributed capacitance of the loudspeaker part of a resistance‐capacitance network. The extremely smooth pressure response resulting from the absence of resonances makes the loudspeaker suitable for the production of transient acoustic signals. Response curves and design data are presented.

ISSN:0001-4966    

DOI:10.1121/1.1917155

出版商:Acoustical Society of America    

年代:1950

数据来源: AIP

摘要:

A method is described for measuring velocity and attenuation of ultrasonic waves in a rubber lamina in a solid ultrasonic transmission line. The method is less convenient than liquid‐path techniques previously described but has the advantages (a) that measurements are made possible at low temperatures where the large viscosity of liquids creates difficulty; (b) that transverse (shear) waves can be studied provided the sample is rigidly bonded into the transmission line. Pulse techniques are used. A buna‐N (Hycar OR‐15) vulcanizate is studied at frequencies of 2, 5, and 10 Mc, and at temperatures from −90°C to 75°C. At constant frequency the attenuation for bulk (longitudinal) waves becomes relatively temperature‐insensitive below the range of appreciable dispersion (e.g., below −30°C at 10 Mc). Complementary shear‐wave measurements indicate that compressional viscosity is always much less important than shear losses as a cause of bulk‐wave attenuation; the relatively constant low temperature bulk‐wave attenuation appears to result from a shear “viscosity” which is not strongly temperature‐dependent but which decreases with increasing frequency. Numerical values for compressional viscosity are not given by present results because sample‐to‐solid bonds employed in shear‐wave measurements introduce uncertainty in the data. The compressional modulus is found to be nearly independent of temperature.

ISSN:0001-4966    

DOI:10.1121/1.1917162

出版商:Acoustical Society of America    

年代:1950

数据来源: AIP

摘要:

The transmission of sound in the ocean has recently been investigated by two methods. In one, a transducer mounted on a submarine served as a sound source of controllable depth, range, and frequency. A string of six hydrophones suspended from a surface vessel enabled the sound field to be measured at six different depths. Measurements at eight and sixteen kilocycles were obtained on a cruise in Caribbean waters and have been plotted as transmission anomaly cross sections showing contours of equal sound level after the removal of spherical divergence. In the other method, the submarine was replaced by a surface vessel from which a sound projector could be lowered to specified depths. This method, employed on a cruise in Middle Atlantic waters, permits longer ranges to be reached, but yields a density of data insufficient for contouring. A second method of lucidly representing the sound field is given.

ISSN:0001-4966    

DOI:10.1121/1.1917166

出版商:Acoustical Society of America    

年代:1950

数据来源: AIP