Suggested modifications to the American Society for Testing and Materials E‐477.

Abstract

ASTM E‐477 is the current standard test method used in North America for evaluating the acoustic and aerodynamic performance of duct silencers. The test method uses, at a minimum, a source chamber, a test duct (that includes a test specimen), and a reverberation chamber. If testing under flow is desired, the system also requires a fan chamber that can provided quiet airflow through the test duct. The results of the test method yield silencer insertion loss, self‐generated noise, both as a function of acoustic frequency and flow velocity, and pressure drop. There are several problems with the current test method, some that are being addressed by the ASTM working group that is responsible for the development and maintenance of this standard. This paper will highlight the most significant problems associated with the current standard and propose modifications to the standard that should, if adopted, improve the intra‐laboratory reproducibility of the test results.