The two waves are reflected from to bottom with a time delay and thus create different directions of the air pressure at any local point in the room which is noticed as another direction of the sound reflection by the ear finally. With increased frequency the direction of the newly built wave changes from left to right alternatingly according to the period length of the wave and the fractional delay added by the reflecting elements.

This method can be used to super impose more than one waves leading to the classical sound diffusors invented by Manfred Schroeder already in the 1960tes. Below 12 partial waves of a N11 diffusor are analyzed having the structure 0,1,4,9,5,3,3,5,9,4,1,0 for the relative fractional offsets. These integer numbers were derived from a modulo operation and make sure that only multiples of the partial waves are used which is essential with this kind of diffusers.

Although this is only a 2D-Simulation, it shows the distribution of the different frequencies in the room. Strong deviation appears for all of the frequencies in the region of the so called design frequency of the diffusor. Almost 180° degrees are covered in theory within one octave being repeated of each octave below and beyond it.

 Here is an example of the integer numbers used for Schröder diffusers: The pattern derived from the modulo operation is repeated regularly with the number of the well. For the real diffuser any cut out can be used theoretically. For practical usage one will select a symmetric slice most probably.

This page was imported from my German web www.solastudio.de

© 2001 J.S.