Technical Note: Test Procedure and User Interface for Determination of the Acoustic Properties of Materials Using the Two-Microphone Transfer Function Method

Abstract

There are many different methods to determine the acoustic properties of materials by exposing them to sound fields and measuring the effects caused by their presence. Test methods have to be executed according to the appropriate Standards, which specify well-defined acoustical conditions and specific instrumentation, to ensure a high and known degree of repeatability and reproducibility. In this technical note, the two-microphone transfer method, based on the standing wave impedance tube method, is described as a procedure for determining the absorption coefficient, reflection coefficient, surface impedance and surface admittance of materials. This method provides a simple and convenient procedure for determining the acoustic properties materials at normal incidence. It is both a fast and accurate method applicable over a large frequency range. The theoretical background of the method, based on the transfer function between two microphones is discussed. To check the reliability of the measurement results, tests were conducted on a sample of typical acoustic material.