Cross‐spectral method of measuring acoustical intensity—correcting phase mismatch error by calibrating two microphone systems

Abstract

The accuracy of measuring acoustic intensity using two closely spaced microphones by correcting the phase mismatch error by measuring the transfer function between the two microphone systems is examined. The two measuring microphone instrumentation systems were calibrated by flush mounting the two microphones in a rigid circular plate attached to the end of a long length of circular pipe. A random noise source was mounted at the other end of the piping system. The two microphones were exposed to the same noise (phase and pressure levels) over a wide range of frequencies. The accuracy of the measurement method was verified by creating a sound field in an anechoic room by a loudspeaker and generating plane‐wave propagation inside along length of pipe with an anechoic termination. The measurement accuracies were very satisfactory. This method has the advantage of eliminating the recording and processing of two sets of data required in circuit switching technique.