This circuit activates a relay for a set duration when a sound is detected above a certain level.
The length of time the relay is activated can be adjusted with VR1 on the Monostable.
The sensitivity of the switch (level of sound it responds to) can be adjusted with VR1 on the Mic Amplifier.
Any device up to 24v at 3A can be connected to the contacts.
VR1 sets the sound level to trigger on - c/w increases sensitivity.
Adjusting VR1 will have a little effect on the response time, but not much - set midway.
Set to Range 2 (0.05s - 2.5s), VR1 midway,
or Range 3, (2.4s+)