Piezzo buzzer and ultrasonic sensor

buzzer.ino

// Add ultrasonic distance sensor library
#include <NewPing.h>

// Disntance sensor
static const int echo_pin = 2;
static const int trigger_pin = 3;
static const int max_distance = 200;

// Piezzo buzzer
static const int piezo_pin = 11;
static const int beep_duration = 10;
static const int beep_frequency = 1000;

// Initialize the ultrasonic sensor
NewPing sonar(trigger_pin, echo_pin, max_distance);

// This functions only runs once
void setup() {
  Serial.begin(9600);
}

// This functions runs in a loop
void loop() {
    // Make a 1000 Hz and 10 millisecond beep
    tone(piezo_pin, beep_frequency, beep_duration);
    // Get the ultrasonic sensor distance
    int distance = sonar.ping_cm();
    // Send the distance reading to the computer
    Serial.print("distance: ");
    Serial.println(distance);
    // When the sonar gives 0, it means it
    // didn't receive a response back, so
    // we set the distance to 1000
    if (distance == 0) {
      distance = 1000;
    }
    // Wait "distance" milliseconds
    delay(distance);
}