Sound Sensor Module
Besides GND and 5V input, there is a pin named "A" which can output a analog value, and a pin named "D" which can output a digital value(0 or 1). The value of the analog output is based on two parameters: the environment sound level and the gain which can be set by the potentiometer named "GAIN". The potentiometer named "Gain" is used to regulate the amplifying times of the LM386 audio amplifier. The potentiometer named"THRESHOLD" is used to set the threshold of the digital output(at which environment sound level pin D will output a HIGH voltage).