Traversing Microphone Spectroscopy as a Means for Assessing Diffusion

Traversing microphone (TM) spectroscopy provides a rapid and sensitive means for assessing sound diffusion in rooms. TM spectra are power spectra obtained at the terminals of a small microphone during its traverse through a room at constant speed. The TM spectral shape is a sensitive indicator of the degree of directional diffusion. If the field is perfectly diffuse, the TM spectrum is precisely rectangular. Observed deviations from the ideal rectangular TM spectra are at once symptoms of imperfect diffusion and clues to their causes. The TM spectrum provides a measure of diffusion averaged over the path of traverse rather than at point locations. The present technique is limited to discrete frequencies. The frequencies must be moderate to high, since the path of traverse must be large in wavelength in order to obtain statistically stable results. Quantitative as well as qualitative assessments of diffusion may be possible with this promising new technique. Work supported by ONR, Code 468.