The influence of diffraction on the performance of sound intensity probes has been examined using a boundary element model of an axisymmetric ‘two-microphone’ probe with the microphones in the usual ‘face-to-face’ arrangement. On the basis of calculations for a variety of sound field conditions and probe geometries it is concluded that the optimum length of the spacer between the microphones is about one microphone diameter; with this geometry the effect of diffraction and the finite difference error almost counterbalance each other up to about kΔr _ 2.2 under virtually any sound field condition that could be of practical importance in sound power determination. This corresponds to about 10 kHz for an intensity probe with half-inch microphones, which is an octave above what has hitherto been regarded as the upper frequency limit of this configuration.The numerical results are confirmed by experiments.
|Title of host publication||Proceedings of the Fourth International Congress on Sound and Vibration : http://www.iiav.org/|
|Number of pages||8|
|Publisher||International Institute of Acoustics and Vibration|
|Publication status||Published - 1996|