A three-dimensional sound intensity probe.

Abstract

A commonly used sound intensity probe is one-dimensional, that is, only the sound intensity in the direction of the probe axis is measured. This makes the sound intensity measurement very time consuming if two- or three-dimensional intensities are needed. Very rarely a two- or three-dimensional intensity probe is used for practical applications. A conventional three-dimensional intensity probe consists of six (three pair) microphones, making the probe itself very clumsy. Due to its non-negligible size, the sound field is disturbed and an accurate measurement becomes difficult. A three-dimensional intensity probe was developed that solves this problem. Four 1/4-in. microphones are located at each apex of a regular tetrahedron. Each of them are attached at the tops of four parallel tubes with a 4 mm diameter. When viewed from the front, the four microphones are located at the three apexes and the center of a triangle. The pressure at the center of the tetrahedron is given by the average of the four pressure outputs. The intensities from the center to the four apexes are obtained by use of the average pressure and individual pressure output. These four components are distributed to three (x,y,z) components. Results of numerical calculations that show the accuracy of the algorithm will be given.