| 摘要 |
The specification discloses a pneumatic sound source comprising a pressure chamber for receiving gas and having a controllable valve for opening and closing an outlet port. An electromagnet including an electrical coil is energized to hold the valve in its closed position and is deenergized for releasing the valve for the generation of an acoustic pulse. Current is applied to the coil by way of a normally closed switch which is opened to deenergize the coil. Circuitry is coupled across the coil and is actuated, when the valve begins to move following deenergization of the coil, to allow current to flow through the circuitry to shunt the coil, thereby dampening the magnitude of a transient voltage generated by movement of the valve through the path of the decaying magnetic flux.
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