Arduino Project 2: The Audible Eye Part 2

/*
Alex Glover
Copyright December 2012
The Audible Eye - handheld device that utilizes an ultrasonic rangefinder to determine distance to whatever object the device is pointed at.
Feedback will be delivered to operator via sound - tone will increase pitch for shorter distances, no tones played for extreme distances.

Credit to:
YourDuino SKETCH UltraSonic Serial 1.0
terry@yourduino.com

Uses: Ultrasonic Library (Copy to Arduino Library folder)
http://iteadstudio.com/store/images/produce/Sensor/HCSR04/Ultrasonic.rar
*/

/* Libraries */
#include "Ultrasonic.h"
/* Pin Assignments */
//Pin designated for controlling the emission of ultrasonic 'pings'
#define TRIG_PIN 2
//Pin designated to 'listen' for ultrasonic 'pings'
#define ECHO_PIN 7
//Pin used to drive the audio output through the headphones
#define SOUND_PIN 12
/* Declare objects */
//Create an object of type 'Ultrasonic' and call it 'Sensor,' passing the trig pin and echo pin numbers into the constructor
Ultrasonic Sensor(TRIG_PIN, ECHO_PIN);
/*-----( Declare Variables )-----*/
//Variable to hold the tone value; this value will be calculated first, and then passed to the tone() function
int toneToPlay=0;

void setup()
{
  Serial.begin(9600);
  //Pring the following text to the serial monitor
  Serial.println("The Audible Eye");
  Serial.println("alexdglover.wordpress.com alexdglover@gmail.com");

}
void loop()
{
  delay(200); //20 millisend delay to let echos from room dissipate

  //The sensor occasionally returns 0 incorrectly. 0 would also give us a divide by zero error in the next line of code. To address these issues
  //we use this simple if statement. Basically, if a 0 is returned, we play no tones through the headphones.
  if (Sensor.Ranging(INC) != 0){
    //Calculating the tone to play as 1000 hertz divided by the number of inches. So if the device is one inch away from an obstacle, we play
    //a 1000 hertz tone. If the device is 10 inches away, it plays a 100 hertz tone. Anything greater than 20 inches reduces the tone to almost inaudible.
    toneToPlay=(1000/Sensor.Ranging(INC));
  }
  else{
    toneToPlay=(0);
  }
  //Here we take whatever value toneToPlay was calculated at and pass it into the tone() function. The parameter of 200 is the number of milliseconds to play
  //the tone. The loop takes about 200 milliseconds in total, so if the loop hangs or crashes, the tone won't keep getting played indefinitely.
  tone(SOUND_PIN,toneToPlay, 200);
}