Errors of the Sound Propagation Direction Measured by an Automatic Measurement Technique of Acoustic Intensity

Abstract

This technique uses a new type of intensity probe which consists of two microphones arranged side by side and which are slid back and forth by a small distance in the direction of the microphone axes. This probe is turned twice on its holder axis by steps of a fixed angle for measuring the three components of an acoustic intensity vector. It is the purpose of this paper to investigate, theoretically and experimentally, the error of the sound propagation direction measured by this automatic measurement technique. This error can be calculated from the measurement theory of the probe and the theory of fundamental errors in the acoustic intensity method. The calculated results agree fairly well with the measured ones. These results show that the error in measurement of sound propagation direction is influenced by the incident angle and frequency of the sound incident to the probe. The limit of the error due to these effects was clarified.