Interface definition:
1. AO: sensor analog output
2. GND: ground
3. VCC: power input， range: 3V-24V
4. DO: digital output (comparator output)

Two red LED indicators: POWER and SENSOR
- POWER: indicator lights up when power-on
- SENSOR: When the microphone detects the sound that reaches a certain value， this LED indicator lights on.

1 x Voice Sound Sensor Module