Watson, F. R. Acoustics of Auditoriums. Bulletin of the Engineering Experiment Station, University of Illinois, March, 1914. Jones, L.T. a Modified Method of Measuring C (Paperback)

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1914 Excerpt: ...than the others. Two layers of this material stop less sound than one layer. Repeated measurements gave the same puzzling result. The % m-cork board shows the same phenomenon, but to a less degree. After some consideration, it was decided to investigate other acoustical properties of the samples to see if additional data would explain this anomalous transmission. If incident sound falls on a material, three things may happen. The sound may be partly reflected, partly absorbed and the rest transmitted. If these three fractions are added together, they must equal the incident sound, or T + A+ R = I= 100 per cent. Therefore to know what happens to the incident sound it is necessary to determine the amounts reflected, absorbed and transmitted. On considering the case of the paper-lined hairfelt in the light of this reasoning, it was decided to attempt to measure the reflection of sound. Reflection Of Sound. By moving the parabolic reflector off to one side, the sound was sent obliquely toward the open doorway where it was reflected by the hairfelt and then passed to the Rayleigh resonator which had been moved into the same room with the reflector and placed so as to be directly in the path of the reflected sound. The observer, as in the transmission tests, stationed himself inside the small house and read the deflection of the Fig. 2. Action of a material in reflecting, absorbing and transmitting sound. resonator through the glass window. A small portion of sound was reflected from the sides of the doorway so that, even with no material over the open door space, the resonator gave a small deflection. This was taken as the zero deflection for the other readings. The deflection for ioo per cent. reflection was arbitrarily taken to be the largest deflection obtain...