| 摘要 |
PURPOSE: To sufficiently prevent howling from occurring in a room provided with complicated frequency characteristic. CONSTITUTION: The gain of an amplifier 42 can be increased by a CPU 30 by turning the volume knob (not shown in figure) of an operating part 32 in a direction to increase a sound volume. When the gain is increased gradually, the howling occurs. In such a state in which the hollowing occurs, for example, a digital equalizer 41a is selected. When a prescribed operation is performed, the CPU 30 changes the attenuation frequency of the digital equalizer 41a. When the attenuation frequency is fluctuated in such way, a point in which a howling tone is reduced can be found out. An operator finds out the point in which the howling tone can be minimized, and sets the frequency at that point as the attenuation frequency of the digital equalizers 41a-41c. The similar operation is applied to other two digital equalizers 41b, 41c. |
