The transmission loss of double and triple walls

Abstract This paper is a digest of information obtained about the sound insulation properties of double and triple panels during the course of a program of laboratory measurements of the transmission loss of such panels. The results indicate that there is an optimum width for the air gap between two adjacent septa. It is also shown that the slope of the sound insulation curve is reduced at the frequency of the first standing wave resonance across the air gap. This reduction in insulation efficiency can be controlled by placing sound-absorbing material in the air gap. The addition of a third panel is seen to lead to increased sound insulation at high frequencies. An increase in the sound insulation at low frequencies by the addition of sound absorbant was not observed despite the fact the theory shows that this may be possible.