Plane wave tube

An acoustic duct or plane wave tube is a test facility used in acoustics. Anechoic chambers are typically subject to a low frequency limit, governed by the length of the sound absorbing wedges employed to prevent reflections within the chamber. Test and measurement microphone calibration services are often required to be undertaken at frequencies where anechoic chambers cannot be used effectively. In this case, a plane wave acoustic duct with anechoic termination provides a practical alternative.