The sound detector system has 3 major applications.
SECURITY SYSTEM FOR HOME/OFFICE
The system can be used for home /office security purpose. When a thief or robber tries to enter the home or office, some sort of sound is generated. It may be voice or any other sort of sound. The microphone takes the sound and alarm /LED enabled instantly.
The system can be used as a spy circuit i.e. voice recorder. If we replace the LED with a voice recorder circuit, the voice recorder activated when comparator output goes high. In a secret meeting, if we place the system perfectly then the input voice signal makes the comparator output high. As a result the voice recorder activated and records the entire conversation of the secret meeting.
The system can be used as a clapping switch. If we replace the LED with a relay or BJT, the system acts as a switch. When we clapped, microphone takes the sound and comparator output goes high. As a result, BJT or relay turns on. If we connect this BJT or relay with light, fan or any electrical / electronic instruments, the system can be operated as a clapping switch.