| 摘要 |
PURPOSE:To enable effective detection of gas by utilizing the antiresonance phenomenon generated by a resonance vessel of a Helmholtz type and an interference body of sound. CONSTITUTION:A Helmholtz type resonance vessel 2 has a sound releasing hole 4, and is provided internally with a piezoelectric type oscillator 6. An interference body 12 such as a metallic plate which reflects acoustic waves is provided above the hole 4 at the distance at which antiresonance is most sharply generated in air. If there is no gas, the oscillation ceases entirely and the sound pressure from the vessel 2 is below the ambient noise level and is not detectable. When gas is generated, the oscillator 6 oscillates and the generation of the gas is announced by the sound itself. The sound pressure increases with an increase in the concn. of the gas. The oscillating state is also detected from the circuit current in the oscillating circuit which drives the oscillator 6. A sound absorbing material layer 16 and a silica gel filter 18 for preventing condensation are attached in a case 14. |
