| 摘要 |
PURPOSE:To prevent a speaker used for a silencing device of an exhaust duct from being damaged by an exhaust gas. CONSTITUTION:A sound of a gas flowing through an exhaust duct 22 is picked up by a microphone 24, the phase of the sound signal is inverted by an inverse phase signal generating section, the resulting signal is amplified by an amplifier section 28, the sound is emitted to the duct 22 by a speaker 30 to silence the sound of the duct. The speaker 30 is fitted to a speaker box 30 and a drawn cone 36 comprising a diaphragm 36a and an edge 36b is provided in the speaker box 32 so as to shield a border between a buffer space 34 and the duct air- tightly. The drawn cone 36 is made of a material of heat resistance and corrosion proof. The speaker 30 is not directly exposed in the gas in the duct 22 by the presence of the drawn cone 36 and the drawn cone itself adopts the heat resistance and corrosion proof structure, it is hardly damaged. |
