#define SPEAKER 8


unsigned long cm = 0;

unsigned long readUltrasonicDistance(int triggerPin, int echoPin)
{
  pinMode(triggerPin, OUTPUT);  // Clear the trigger
  digitalWrite(triggerPin, LOW);
  delayMicroseconds(2);
  // Sets the trigger pin to HIGH state for 10 microseconds
  digitalWrite(triggerPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(triggerPin, LOW);
  pinMode(echoPin, INPUT);
  // Reads the echo pin, and returns the sound wave travel time in microseconds
  return pulseIn(echoPin, HIGH);
}

double bpm = 116.0 * 2.0;
double ms_delay;

void setup() {
  pinMode(SPEAKER, OUTPUT);

  ms_delay = 60000.0 / bpm;
}

void loop() {
  cm = readUltrasonicDistance(3, 2);// / 58;

  tone(SPEAKER, cm, 100);
  delay(ms_delay);
}