Iterative equalization of room transfer function using biquadratic filters

Two major difficulties are affronted when one looks for designing a suitable equalizing system for room acoustics. The first difficulty comes from the high variability of room transfer functions (RTFs) depending on the relative source/listener position. The second problem resides in the RTFs themselves, which are characterized by a high mode density specially at high frequencies. This paper presents a fast iterative algorithm for RTFs equalization. In order to overcome the first problem related to RTFs variability, we used the common acoustical poles and zeros (CAPZ) model, which models the common modes to the several RTFs. After obtaining the CAPZ model, we have chosen to design biquadratic notching/peaking filters to equalize the different modes and anti-resonances. The problem in designing biquadratic filters comes from the fact that they can interfere when having central frequencies close enough. The method proposed in this paper overcomes this problem.