4 has proposed equations for both fully anechoic and semi-anechoic chambers by considering the above-mentioned parameters. 3 In order to overcome this error, Blanco et al.

However, the actual cut-off frequency of the chamber depends on other parameters too such as source size, major dimension of chamber, 2 and the length of wedges used. Where f is the cut-off frequency, c is the speed of sound, and L is the length of the wedges used considering that the source size is negligible as compared to the chamber volume. The most widely accepted approximate theoretical formula to determine the cut-off frequency of the chamber is f = c 4 L The theoretical predictions can be done before constructing the anechoic chamber and the chamber can be built accordingly based on the range of frequencies of interest.

This cut-off frequency can be determined experimentally and theoretically. The lower cut-off frequency is defined as the minimum frequency from which the chamber shows its anechoic behavior. Ideally, the anechoic chamber should absorb all the sound incident on it, but it is practically difficult to design and construct an anechoic chamber which could absorb all the frequencies hence, anechoic chambers are generally constructed to provide free-field conditions for a certain range of frequencies. Fully anechoic chambers are those chambers in which all sides, ceiling as well as floor of the chamber are covered with sound absorbing material for completely absorbing the sound in all directions however, in semi-anechoic chambers, one side is not covered (i.e., usually the floor) with the absorbing material and hence provide less sound absorption as compared to fully anechoic one. Anechoic chambers can be classified as fully anechoic and semi-anechoic chambers. To achieve this reflection-free condition, the walls of the room are surrounded by sound absorbing materials, which absorb the sound energy and do not allow reflections to occur. Anechoic chambers are the rooms designed to completely absorb all the reflections of sound and hence provide an eco-free environment.

What is cutoff frequency