The Acoustic Slit

Author: N.H. Crowhurst

The directivity of an acoustic slit radiator

The only way to improve the uneven distribution at different frequencies is to use a different principle altogether. One such is an acoustic-slit radiator. Because the whole length of the slit "puffs" and "sucks" at the same time, it generates a cylindrical wave, with the slit as a center line. The slit will work well provided that its length is greater than half a wavelength, and its width is less than half a wavelength. Thus its length and width fix the range of frequencies for which it is effective.

As an example, a slit 10 inches long and 1 inch wide will be effective between about 600 and 6000 cycles. Below 600 cycles it will be ineffective because of acoustic mismatch (unsatisfactory transition from the slit to free space); above 6000 cycles the radiation begins to concentrate into a beam.