The present invention relates to a method for designing a
modal equalizer (5) for a
low frequency audible range, typically for frequencies below 200 Hz for a predetermined space (1) (listening room) and location (2) (location in the room) therein, in which method
modes to be equalized are determined at least by
center frequency and decay rate of each mode, creating a discrete-time description of the determined
modes, and determining
equalizer filter coefficients on the basis of the discrete-time description of the determined
modes, and forming the
equalizer (5) by means of a
digital filter by defining the filter coefficients on the basis of the properties of the modes. In accordance with the invention following method steps are used: forming a mode detection function (G(Ω)), defining the highest peak
angular frequency Ωp of the function (G(Ω)), making AR analysis of predefined order for solving the poles of the mode representing the highest peak
angular frequency, selecting the pole closest to point ejΩp on the unit circle, determining the
decay time of the mode and if is over a predetermined level, designing a
modal correction filter for this mode, and repeating this procedure until no
decay time exceeds over the predetermined level, and each individual filter obtained in previous stages of the method is combined to a cascaded filter.