ISSN:0001-4966    

DOI:10.1121/1.1916164

出版商:Acoustical Society of America    

年代:1942

数据来源: AIP

ISSN:0001-4966    

DOI:10.1121/1.1916165

出版商:Acoustical Society of America    

年代:1942

数据来源: AIP

ISSN:0001-4966    

DOI:10.1121/1.1916166

出版商:Acoustical Society of America    

年代:1942

数据来源: AIP

ISSN:0001-4966    

DOI:10.1121/1.1916167

出版商:Acoustical Society of America    

年代:1942

数据来源: AIP

摘要:

Measurements on the intensity and the frequency distribution of industrial noises and the hearing losses of industrial workers show: (a) some degree of correlation between the average noise level and the temporary and permanent hearing losses; (b) an almost complete localization of the permanent hearing loss in the region above 1500 cycles (with a maximum at 6000 cycles), while the most important components of industrial noises are practically always below this frequency‐limit; (c) some correlation between the amount of temporary and permanent hearing losses for high frequencies; (d) a very small permanent hearing loss for low frequencies with a very rapid recuperation from temporary loss in this region.

ISSN:0001-4966    

DOI:10.1121/1.1916168

出版商:Acoustical Society of America    

年代:1942

数据来源: AIP

摘要:

A rigorous equation is set up for the velocity of sound in gases. This is used to calculate the velocity of sound in dry air at standard conditions from data taken in independent measurements. The result of this calculation is 331.45±0.05 meters sec.−1An extensive survey of previous reported measurements has been made. After proper corrections are taken into account, the weighted mean is 331.464±0.05 meters sec.−1The results of very precise interferometer measurements by the authors give 331.44±0.05 meters sec.−1.

ISSN:0001-4966    

DOI:10.1121/1.1916169

出版商:Acoustical Society of America    

年代:1942

数据来源: AIP

ISSN:0001-4966    

DOI:10.1121/1.1916170

出版商:Acoustical Society of America    

年代:1942

数据来源: AIP

ISSN:0001-4966    

DOI:10.1121/1.1916171

出版商:Acoustical Society of America    

年代:1942

数据来源: AIP

摘要:

A thorough understanding of the acoustical properties of porous materials is becoming increasingly important because of the wide variety of unusual and important applications in which they are finding use. A simple and useful theory is presented for predicting the normal acoustic impedance of isotropic porous materials in terms of three previously described simple constants, namely, flow resistance, porosity, and effective dynamic mass of the enclosed gas. The variation of normal impedance with angle of incidence for spaced‐out or rigidly backed samples is treated. A striking possibility is discussed, namely, thatgaseous expansions are isothermalover most of the audiofrequency range in materials made of finely divided particles. Many isotropic acoustical materials appear to fall in this class. This means that an air cavity becomeslessstiff to dynamic compression when a very porous finely divided material is added to the cavity than when the material is not present. The results are checked against experimental data. A simple method is described for measuring the porosityPof a material, namely, the ratio of the volume of the air spaces in a material to the total volume of the material.

ISSN:0001-4966    

DOI:10.1121/1.1916172

出版商:Acoustical Society of America    

年代:1942

数据来源: AIP

ISSN:0001-4966    

DOI:10.1121/1.1916173

出版商:Acoustical Society of America    

年代:1942

数据来源: AIP