Noise-Driven Sound Generator

 


G. Kleine


The sound generator shown here uses its built-in loudspeaker as a microphone when it is in the standby state. As soon as it detects a noise that exceeds an adjustable threshold level, it becomes active. This small, clever circuit can be used as an alarm generator that reacts to noises. You can also use it to help you locate an object in response to a loud sound, such as clapping your hands or whistling loudly.


The gate at the bottom of the schematic diagram acts as a lin¬ ear low-frequency amplifier, due to the negative feedback resistor R3. It receives its input signal from loudspeaker LSI, which acts as a microphone when T1 is cut off. The amplified


Generator

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