### Project 11 Voice-activated

**1.Project instruction**

Akin to a microphone, sound sensor can receive sound waves and show the vibration image of sound but not to measure the intensity of noise. It has a built-in condenser electret microphone that is sensitive to sound.

The sound waves vibrate the electret film in the microphone, which causes the change of capacitance, and generates a correspondingly changed tiny voltage. This voltage is then converted into a 0-5V voltage, received by the data collector after A/D conversion, and sent to Arduino UNO.

**2.Project Principle**

- Use 5v DC power supply (working voltage 3.3V-5V)
- With analog output AO, real-time microphone voltage signal output
- High sensitivity, electret condenser microphone (ECM) sensor
- Can detect the sound intensity of ambient environment.

Note: This sensor can only identify the presence or absence of sound (according to the principle of vibration) and cannot identify the size of the sound or the sound of a specific frequency.

**3.Project circuit**

![](media/image-20260127134958676.png)

**4.Project code**

```c
const int SOUND_PIN = A7;
const int LED_PIN = 13;

void setup() 
{
  pinMode(LED_PIN, OUTPUT);
  Serial.begin(9600);
}

void loop() 
{
  // read A7 analog signal 
  int value = analogRead(SOUND_PIN);
  // output signal value
  Serial.println(value);
  if(value > 5)
  {
    // more than threshold, pin 13 is high level and LED on    digitalWrite(LED_PIN, HIGH);
    delay(100);
  }
  else
  {
    // less than threshold, pin 13  is low level and LED off
    digitalWrite(LED_PIN, LOW);
    delay(100);
  }
}
```