| 摘要 |
PURPOSE:To prevent howling and to attain excellent silencing by arranging an echo prevention tube between an active sound source and an opening through which a sound of an open case radiates. CONSTITUTION:A peripheral face of a duct 1 being an open case is provided with a sound source 2 and an active sound source 5, and the active sound source 5 provided toward an opening end 1a from the sound source 2 is provided with a sensing microphone 3 arranged between the sound source 2 in the duct 1 and the active sound source 5 and a convolution integration device 4. Moreover, the echo prevention tube 6 is arranged between the active sound source 5 in the duct 1 and the opening end 1a through which sound radiates and the sound radiating from the active sound source 5 radiates to the outside of the opening end 1a through the tube 6. Thus, the sound radiating from the active sound source 5 is not sensed by the sensing microphone and the howling is prevented. |
