| 摘要 |
PURPOSE:To prevent howling by controlling the sound volume of a speaker corresponding to a coefficient updating process for dummy echo generation even unless the coefficient updating process follows up a sudden change in sound field. CONSTITUTION:If the echo and sound field of a conference room changes suddenly, the coefficient updating process of a dummy echo generation part 4 can not follow up the change and when residual echo data outputted from a composition part 8 temporarily increases, a residual echo detection part 8 monitors the residual echo on the basis of a certain threshold value. When the threshold value is exceeded, that is reported to a host CPU 3, which controls a variable resistor 6 for controlling the sound volume of the speaker 11 to lower the sound volume of the speaker 11, thereby preventing howling caused by the sudden change in sound field. |
