Device for correcting frequency characteristic of sound field

Sound field frequency characteristic compensation apparatus comprising an input unit (1) for entering object data of gain values respectively at a plurality of predetermined frequency points in a sound field frequency band, the gain values specifying an object frequency characteristics for compensation, a processing unit (2) for determining parameters which define filters to be set according to the object data of gain values entered by said input unit, and a variable filter unit (4) for setting filters on the basis of the determined parameters to approximate the object frequency characteristics with synthesized frequency characteristics of the set filters, wherein

• (1) said processing unit determines a first filter of peaking type or notch type which has a center frequency equal to the frequency point associated with the maximum or minimum gain value in the object data, and gain and peak factor estimated according to the object date of gain values,
• (2) said processing unit obtains error values between the frequency characteristics of the determined first filter and the object frequency characteristics at the frequency points in each of sub-bands which are assigned by dividing the sound field frequency band and determines one sub-band having the maximum total error which is the total of error values in that sub-band,
• (3) said processing unit determines a second filter which has a center frequency equal to the frequency point associated to the maximum or minimum error value in said determined one sub-band, and gain and peak factor estimated according to the error values, and
• (4) said processing unit obtains error values between the synthesized frequency characteristics of the determined first and second filters and the object frequency characteristics at the frequency points in the sound field frequency band, determines one sub-band having the maximum total error except for a case where the obtained error value for every frequency point is within a predetermined tolerance, and repeats the above steps (3) and (4) to sequentially determine parameters for a third, a forth . . . filters.