Sound Diffraction by a Slit between Two Half Infinite Planes

Abstract

This paper mainly deals with the problem of sound diffraction by the slit which exists between two half infinite planes. The planes are located between a point source and a receiver in the arrangement that the edges of the planes are in parallel holding certain distance.
At first, a rather complicated formula to predict the amount of diffraction effect was derived based on Keller's geometrical theory of diffraction almost exactly.
Secondly an approximate formula, simpler and more practical, was derived from the above formula.
Calculated values from there two formulae were almost the same. The results of calculation using the formulae agreed well with the results of calculation using a boundary element method in two dimensions, except the case where multi reflections are supposed to occur between two planes.
It was also confirmed that the simpler formula can be used to predict double diffraction by two thin barriers.