This circuit makes an incandescent lamp blink in order to vary its brightness with a candle effect. The circuit is from an old Popular Electronics, but the components used are current.
This circuit makes use of a low impedance microphone. The relay is according to the supply voltage...
This circuit was found in an old Radio Electronics, but can still be assembled as the components are...
Any small sound amplifier from 200mW to 1W can be used in this simple circuit. Or circuit of two...