Measurement of sound intensity using a phase- and amplitude-correcting FFT algorithm

An amplitude and phase correction algorithm is developed for use with the single mechanically damped pressure-gradient velocity microphone of Riedlinger (1984) and the acoustic-intensity-meter software and hardware of Riedlinger et al. (1984); a calibration apparatus simulating a free plane progressive wave is described; and the results of experimental tests of the correction algorithm are reported. In the calibrator, four identical loudspeakers are mounted at the corners of a square housing, directed at the test probe in the center of the square, and fed with the same signal; but one speaker is connected 180 deg out of phase. The correcting algorithm is found to permit corrections of up to 15 dB and 30 deg of channel mismatch, although some limitations apply in practice.