led switch based on brightness sensor and mic.

gistfile1.c

#include <Wire.h> 
#include <math.h>

int BH1750address = 0x23;
byte buff[2];
int mic_pin = 2;  
int switch_pin = 13;
bool is_on = false;

void setup()
{
  Wire.begin();
  Serial.begin(9600);
  BH1750_Init(BH1750address);
  delay(200);
  pinMode(mic_pin, INPUT);
  pinMode(switch_pin, OUTPUT);
  digitalWrite(switch_pin, LOW);
}

void loop()
{
  static byte i = 0;
  int sound = analogRead(mic_pin);

  // sound level 100
  sound > 100 ? i++ : i = 0;

  // sound big enough to last 4 measurement run
  if (i > 4) {
    uint16_t brightness = 0;
    if (BH1750_Read(BH1750address) == 2)
    {
      brightness=((buff[0]<<8)|buff[1])/1.2;
      Serial.println(brightness,DEC);

      // brightness level 200
      if (brightness < 200 && !is_on) {
        digitalWrite(switch_pin, HIGH);
        is_on = true;  
      }
    }
    i = 0;
  }
  delay(50);
}

int BH1750_Read(int address)
{
  int i=0;
  Wire.beginTransmission(address);
  Wire.requestFrom(address, 2);
  while(Wire.available())
  {
    buff[i] = Wire.read(); // receive one byte
    i++;
  }
  Wire.endTransmission();
  return i;
}

void BH1750_Init(int address)
{
  Wire.beginTransmission(address);
  Wire.write(0x10);//1lx reolution 120ms
  Wire.endTransmission();
}