| 主权项 |
1. A diffracted sound reduction device that controls sound pressures at a plurality of control points which are positions including a listener's position, the diffracted sound reduction device comprising:
a reproduction speaker that outputs reproduced sound having properties indicated by an input signal; at least two control speakers each of which reproduces a corresponding one of control signals which indicates properties of control sound to reduce a sound pressure of diffracted sound, the diffracted sound being a part of the reproduced sound and arriving at a corresponding one of the control points except the control point at the listener's position; and control filters, each of which filters the input signal to generate the corresponding one of the control signals, wherein the reproduction speaker faces a listener, the control speakers do not face the listener, each of the control points faces a corresponding speaker from among the reproduction speaker and the control speakers, each of the control filters generates the corresponding one of the control signals to cause a sound pressure of the diffracted sound at the corresponding one of the control points to be lower than a sound pressure of direct sound that is a part of the reproduced sound and that arrives at the control point at the listener's position, each of the control filters has a filter coefficient determined by a filter coefficient determination method including performing signal processing on the input signal to determine, for the corresponding one of the control points, a desired signal indicating properties of desired sound to be eventually reproduced at the corresponding one of the control points, in the performing of the signal processing to determine the desired signal, the desired signal is determined, for each of the control points, from the input signal by using a corresponding one of level adjusters and a corresponding one of desired property filters, for a first desired property filter from among the desired property filters, a transfer characteristic of sound transfer from the reproduction speaker to the control point at the listener's position is set, and for each of the desired property filters except the first desired property filter, a transfer characteristic of sound transfer from the reproduction speaker to the corresponding one of the control points at the positions except the listener's position is set, each of the level adjusters adjusts a gain of the input signal according to a setting value, and the filter coefficient determination method further includes: applying, for each of the control speakers, the corresponding one of the control filters on the input signal to generate the corresponding one of the control signals to be reproduced by the each of the control speakers; calculating, for each of the control points as an acoustic simulation, a reproduction signal indicating properties of the desired sound based on the generated corresponding one of the control signals; synthesizing, for each of the control points, the desired signal and the reproduction signal to generate an error signal, the desired signal being an output signal in the performing of the signal processing to determine the desired signal, and the reproduction signal being an output signal in the calculating of the reproduction signal; updating the filter coefficient of the corresponding one of the control filters to minimize the error signal, when the generated error signal is greater than or equal to a predetermined threshold value; and determining the filter coefficient of the corresponding one of the control filters to be used, when the error signal is smaller than the predetermined threshold value. |
