ABSTRACTS OF TECHNICAL ARTICLES 403 



nary solutions, by their different energy relations, may cause the ob- 

 served effects on the rate of precipitation of antimony. 



The Tube Method of Measuring Sound Absorption Coefficients.^^ 

 E. C. Wente. The general principles underlying the tube method 

 of measuring sound absorption can be derived conveniently from the 

 analogous equations for the electrical transmission line. These equa- 

 tions show that the actual method of measurement is capable of many 

 modifications, some of which have already been adopted by various 

 experimenters. However, if reliable results are to be obtained, it is 

 important that the apparatus be so designed that the propagation 

 along the tube be rectilinear and the attenuation small, and that the 

 tone be kept free from harmonics. 



In the tube method the absorption is measured at perpendicular 

 incidence, whereas in the reverberation method it is measured at ran- 

 dom incidence. A theoretical study of the absorption of sound by por- 

 ous materials as a function of the angle of incidence shows that in some 

 cases there may be a considerable discrepancy between the values 

 obtained by the two methods. The tube method may also give im- 

 practicable results for materials which are to be used in the form of 

 large panels and absorb sound largely by virtue of inelastic bending 

 rather than because of their porosity. 



" Jour, of the Acoust. Sac. of Amer., Oct. 1929. 



