//declare the sound sensor pin connection
#define SOUND_PIN A0
//eight leds in total
#define LED_COUNT 8
//declare LED pin connections
int LED_PINS[] = {4,5,6,7,8,9,10,11};

//LED index
int thisLED = 0;
//voltage of the sound sensor
int sound_voltage = 0;
//number of the lit LEDS
int lit_LED = 0;


void setup() {
  // put your setup code here, to run once:
  //led pin-mode initialization
  for(thisLED = 0; thisLED < LED_COUNT; thisLED++)
  {
    pinMode(LED_PINS[thisLED], OUTPUT);
  }

}

void loop() {
  // put your main code here, to run repeatedly:

  //Read the voltage of the sound sensor
  sound_voltage = analogRead(SOUND_PIN);
  //quantify sound_voltage
  lit_LED = map(sound_voltage, 0, 1023, 0, LED_COUNT);

  //light the leds
  for(thisLED = 0; thisLED < LED_COUNT; thisLED++)
  {
    if(thisLED < lit_LED)
      digitalWrite(LED_PINS[thisLED],HIGH);
    else
      digitalWrite(LED_PINS[thisLED],LOW);
  }  

}