const byte numSensors = 3;
const byte ECHO_PIN[numSensors] = {2, 5, 8};
const byte TRIG_PIN[numSensors] = {3, 4, 7};

void setup() {
  Serial.begin(115200);
  pinMode(LED_BUILTIN, OUTPUT);
  for (byte s=0; s<numSensors; s++) {
    pinMode(TRIG_PIN[s], OUTPUT);
    pinMode(ECHO_PIN[s], INPUT);
  }
}

float readDistanceCM(byte s) {
  digitalWrite(TRIG_PIN[s], LOW);
  delayMicroseconds(2);
  digitalWrite(TRIG_PIN[s], HIGH);
  delayMicroseconds(10);
  digitalWrite(TRIG_PIN[s], LOW);
  int duration = pulseIn(ECHO_PIN[s], HIGH);
  return duration * 0.034 / 2;
}

void loop() {
  ledVariable=map(vol,2,400,0,255);
  bool isNearby = false;
  Serial.print("Measured distance: ");
  for (byte s=0; s<numSensors; s++) {
    float distance = readDistanceCM(s);
    isNearby |= distance < 100;
    Serial.print(distance);
    Serial.print(" ");
  }
  Serial.println();
  digitalWrite(LED_BUILTIN, isNearby);
  delay(100);
}