Special intensity probes

Sound intensity is a vector quantity that describes the direction and magnitude of the flow of sound energy. A standard intensity probe measures the magnitude of the intensity vector in only one dimension, i.e. in the direction along the axis of the probe. To describe a sound-intensity vector fully, the intensity needs to be measured in at least three mutually perpendicular directions. This will give a complete description of the vector in an orthogonal system of co-ordinates and the resultant magnitude and direction of the sound intensity vector can then be calculated.

The acoustical separation between the two microphones in a probe normally limits the operating frequency range of a sound intensity probe. The frequency range is related to the wavelength of the sound as well as the magnitude of its intensity relative to its sound pressure. Since the wide-band intensity probe has two pairs of intensity microphones, it can simultaneously measure with two different acoustical separations between microphones and thereby extend the useful frequency range.