| 摘要 |
PURPOSE:To facilitate a sound field control by controlling only a sound pressure on a border face of an area desired to be controlled so as to control the entire area thereby eliminating the need for the use of a point sound source and eliminating the need for the recognition of a sound pressure gradient on the border face in the direction of a normal of the border face. CONSTITUTION:When a desired signal is zero, a sound coming externally to a control sound source is picked up at first by microphones 5, 6, added respectively through filters 7, 8 and outputted from a speaker 4 through a filter 9. Since the sound at the position of the microphone 6 is cancelled out with the sound from the speaker 4 with the filter 9, the sound at the position of the microphone 6 is always zero. When a desired signal exists, since the external sound is cancelled at the position of the microphone, only the sound by the desired signal is obtained and the sound pressure at the microphone 6 is optionally controlled. Thus, it is not necessarily required to use a point sound source and not required to recognize the sound pressure gradient, then the sound field control is facilitated. |
