摘要:

A formula is derived that is applicable to the evaluation of light pattern measurements when non‐parallel light is used. It is shown that deviation from parallelism encountered in the laboratory may cause Buchmann and Meyer's simplified formula to be in error by several db. Numerical examples are given, and the results are extended to vertical and loop recordings.

ISSN:0001-4966    

DOI:10.1121/1.1916415

出版商:Acoustical Society of America    

年代:1947

数据来源: AIP

ISSN:0001-4966    

DOI:10.1121/1.1916416

出版商:Acoustical Society of America    

年代:1947

数据来源: AIP

ISSN:0001-4966    

DOI:10.1121/1.1916417

出版商:Acoustical Society of America    

年代:1947

数据来源: AIP

摘要:

Earlier studies have classified deafness cases into two general groups, those having functional disorders of the middle ear and those having impairments resulting from atrophy of the nerve fibers terminating along the basilar membrane (conductive and nerve deafness types, respectively). Such classifications have been made using bone conduction threshold measurements and unilateral loudness balance results as the basis for differentiation. Bone conduction results, however, are often subject to considerable error while the unilateral loudness balance technique can only be applied to individuals having one normal and one impaired ear. These limitations introduce a need for a completely independent monaural method of classifying deafness types. This is particularly true for the selection of candidates suitable for the fenestration operation for the restoration of hearing in otosclerosis (immobilized stapes). The present paper is concerned with an investigation of short time auditory fatigue as a method of obtaining an impairment analysis. In this study, it was found that the fatigue of the conductively deafened observer was similar to the normal observer except the onset of fatigue was shifted by the amount of the threshold loss. For the nerve deafened observer, on the other hand, the onset of fatigue was found to occur at normal intensity levels. The occurrence of excessive fatigue in one of the nerve type impairment cases investigated appears to offer additional information on the nature of the lesion.

ISSN:0001-4966    

DOI:10.1121/1.1916418

出版商:Acoustical Society of America    

年代:1947

数据来源: AIP

摘要:

The following paper contains investigations into the resonance sharpness of acoustic resonators. Experimental and theoretical results are compared and found in good accordance.

ISSN:0001-4966    

DOI:10.1121/1.1916419

出版商:Acoustical Society of America    

年代:1947

数据来源: AIP

摘要:

Acoustic techniques are well suited to determining the effective dynamic values of elastic and viscous coefficients for rubber‐like materials. The values of these coefficients vary with frequency, and the effective dynamic modulus is, in general, larger than the modulus determined from stress‐strain curves. Because acoustic attenuation for waves involving shear is large in rubber‐like materials, the elastic and viscous coefficients must be computed from rigorous relations involving both sound phase velocity and attenuation rather than from the approximate relations which are often used. The necessary relations for computing Young's modulus and the associated viscosity coefficient from acoustic data are presented. An experimental method is described which has been used to measure the sound phase velocity and attenuation of longitudinal waves in thin narrow samples in the frequency range from one to 26 kilocycles. A vibration generator excites one end of a sample held under small tension, while a receiving element moves along the strip. Records of sound intensity and of phase as a function of distance are plotted automatically, and acoustic attenuation and phase velocity are determined from the records. The r.m.s. error in attenuation measurements ranges from 6 to 12 percent over the frequency range. The r.m.s. error in velocity measurements ranges from 2 to 9 percent. Sample acoustic data and the resulting elastic and viscous coefficients are given for a carbon‐black buna‐N cement.

ISSN:0001-4966    

DOI:10.1121/1.1916420

出版商:Acoustical Society of America    

年代:1947

数据来源: AIP

ISSN:0001-4966    

DOI:10.1121/1.1916421

出版商:Acoustical Society of America    

年代:1947

数据来源: AIP

ISSN:0001-4966    

DOI:10.1121/1.1916422

出版商:Acoustical Society of America    

年代:1947

数据来源: AIP

摘要:

This paper presents results of studies in atmospheric ultrasonics in unforested areas in the tropics and in the temperate zone. Data of practical interest in regard to the possibilities of ultrasonic signaling were obtained. Fundamental ultrasonic phenomena of propagation were investigated and their causes isolated through correlations with simultaneously observed micrometeorological phenomena. It was found that at times the open air is a scattering, as well as absorbing, medium. Values of absorption coefficients are presented for frequencies up to 30 kc.

ISSN:0001-4966    

DOI:10.1121/1.1916423

出版商:Acoustical Society of America    

年代:1947

数据来源: AIP

摘要:

Extensive measurements have been made, at ten megacycles, of the temperature dependence of ultrasonic velocity in liquids and liquid mixtures. All single liquids tested, except water, were found to have large negative temperature‐coefficients in the temperature range of zero to 80°C. Water has a large positive coefficient at room temperature, decreasing to zero at 74°C and then becoming negative (with a peak velocity of 1557 meters/sec.). Solutions in water of various other liquids (and of some solids) give parabolic velocityvs.temperature curves like that for water but with the peak velocity and peak temperature values shifting with the concentration of the solution. In general increasing the concentration raises the peak velocity slightly and lowers the peak temperature markedly from the values for water alone. It has also been found possible by compounding three‐component solutions to adjust the values of the peak velocity and peak temperature independently within a narrow range of velocities and a wide range of temperatures.

ISSN:0001-4966    

DOI:10.1121/1.1916424

出版商:Acoustical Society of America    

年代:1947

数据来源: AIP