• Detecting loud sounds in an ambient environment

• Uses an electret condenser microphone to convert sound energy into an electrical signal

• Electret condenser microphone is a parallel plate capacitor and works on the principle of a variable capacitance.

• Microphone consists of two plates, one fixed (called the back plate) and the other moveable (called the membrane) with a small gap between them.

• When sound signal vibrations falls on the membrane through the hole, the sound strikes the membrane and it starts moving, thereby changing the capacitance between the plates which in turn results in a variable electric current to flow.