Extension of frequency range of the sixteen-microphone method in normal-incidence sound transmission loss measurement.

Abstract

This study deals with development of a high-frequency measurement method of normal incidence sound transmission loss using acoustic impedance tube. On ordinary transfer-function method, measurable frequency of the method is limited by the diameter of the tube. Authors have developed 8 microphone method to measure normal incidence absorption coefficient. This technique lays 4 microphones on the same cross section and cancels rotational acoustic modes. This makes it possible to measure normal incidence absorption coefficient up to 3 times the upper frequency of the ordinary 2 microphone method. In this study, authors apply the same technique to normal incidence transmission loss measurement.