42 ILLINOIS STATE ACADEMY OF SCIENCE 



that amplitudes of vibration of the same order as atomic 

 dimensions, namely 10"^ cms., produce the sensation of 

 sound. The extension of the method to other problems of 

 audition promises to yield much valuable information 

 upon a subject in which such knowledge is badly needed. 



These are some of the problems that have been at- 

 tacked and partially solved during the three years of the 

 Laboratory's existence. Beginnings have been made 

 upon others, and there is still a large group for the 

 study of which the Laboratory affords most excellent 

 facilities. One of the most fundamental of these is the 

 development of standard sources of sound of easily 

 measurable acoustical output. An equally fundamental 

 desideratum for acoustical measurements is a means of 

 measuring sound intensity as energy, simply, independ- 

 ently of its pitch. All of our sound measuring devices 

 give readings that are functions of both pitch and in- 

 tensity, so that both of these factors must be taken into 

 account in acoustical measurements as now made. The 

 status of our present investigational methods is that 

 which existed in the measurement of radiation before 

 the development of the bolometer and the sensitive 

 thermo-couple. Rapid advance in the quantitative study 

 of acoustical problems awaits the development of cor- 

 responding means for sound measurement. The meas- 

 urement of noise, which is sound without definite pitch 

 characteristics, is at present impossible. 



One of the outstanding lessons of the war was the dis- 

 covery of the military and naval possibilities of acous- 

 tical methods. Equally impressive was the discovery 

 of the entire inadequacy of our quantitative knowledge 

 of this branch of Physics. The control and reduction of 

 sound becomes one of vital importance in view of the 

 multiplication of sources of noise in this mechanical age 

 and the increasing congestion of living and working con- 

 ditions of modern life. Hence research in Acoustics 

 offers a pleasant prospect of contributions of practical 

 value to scientific knowledge, and a laboratory devoted 

 to this purpose should fill a useful place in the scheme of 

 things scientific. 



