The experiments were carried out in an anechoic chamber. This is typically illustrated by a reduction in the level of fluctuations in the emitted acoustic pressure spectra. These fluctuations are normally associated with interference between the sound emitted by the front surface of the speaker and by that emitted from the back. The results also suggest that the interference pattern in the air gap is altered by the porous layer, so that some individual resonances in the acoustic pressure spectra which inevitably occur between the rigid base and the vibrating plate can appear suppressed. A numerical simulation was carried out to model this effect.
Every polynomial can represent the denominator of the transfer function of an electrical filter.
The product of remaining polynomials forms the denominator of the transfer function of a non-symmetrical loudspeaker system. Then, various combinations of these polynomials give various possibilities of realization of the entire system.