Sound power measurements using intensity at highfrequencies

摘要

Some years ago it was shown that the sound intensity estimated with a twomicrophone probe with half-inch microphones separated by a 12-mm spacer is reliable up to 10rnkHz, which is about an octave higher than the upper limiting frequency determined by the finite difference error. The explanation for this surprising finding was that the effect of scattering and diffraction tends to cancel the finite difference error for this particular configuration. On the other hand, the mean sound pressure determined with the intensity probe, and thus the measured pressureintensityrnindex, will typically be underestimated at high frequencies. However, a recent investigation has demonstrated that it is possible to improve the mean pressure estimate using a different weighting of the pressure signals of the two microphones. The improved intensity probe can measurernthe sound pressure more accurately at high frequencies than an ordinary sound intensity probe or an ordinary sound level meter. This paper examines the performance of the improved sound pressure estimate in sound power measurement using sound intensity.