This Clap switch circuit using IC 555 is a hobby circuit, makes LED to glow while you clap or make louder noise. You can use this circuit concept in many ways to activate sound based project.
This construction will give mono pulse when trigger received from mic, the duration of pulse time varies respect to R2 and C2 connected with IC555.
The condenser mic reacts as sound sensor, this will produce voltage oscillation when the loud sound produced. Those voltage oscillation signals are amplified by two stage (BC547) amplifier and given into triggering input of IC555. When receiving triggering input the timer IC makes mono pulse depends on timing resistor and timing capacitor (R2, C2). Here output drives LED, we can connect buzzer or relay as required for our need.