/*  Listing 13-3. Ultrasound Sensor Program
  Code is taken from 
     http://www.arduino.cc/en/Tutorial/Ping
  and was written by David Mellis and modified
  by Tom Igoe.

  Modified by Dr. Purdum for sound speed at
  72 degrees F.
  1/2/2105
*/

int triggerPin = 8;
int echoPin = 10;

void setup() {
  Serial.begin(9600);
  pinMode(triggerPin, OUTPUT);
  pinMode(echoPin, INPUT);
}

void loop(){
  long roundTrip;
  float cm;
  
  digitalWrite(triggerPin, LOW); // Trigger a short low pulse 
  delayMicroseconds(2);          // before the HIGH pulse
  digitalWrite(triggerPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(triggerPin, LOW);
  
  roundTrip = pulseIn(echoPin, HIGH);
  cm = microsecondsToCentimeters(roundTrip);
  float inch = cm / 2.54;         // Figure out inches
  Serial.print(cm);
  Serial.print(" cm or ");
  Serial.print(inch);
  Serial.print(" inches");
  Serial.println();
  delay(1000);
} 
/*****
  This function calculates how far the pulse travels to
  strike and object and return. The air temp is assumed
  to be 72F.
  
  Parameter list:
    long microseconds    the time of the pulse
    
  Return value:
    float                centimeters to and from target
    *****/
float microsecondsToCentimeters(long microseconds){
  return (microseconds*0.034495)/2;
}




Expected output:
143.67 cm or 56.56 inches
144.03 cm or 56.71 inches
116.90 cm or 46.03 inches
46.95 cm or 18.48 inches
46.71 cm or 18.39 inches
30.29 cm or 11.92 inches
17.30 cm or 6.81 inches
9.14 cm or 3.60 inches
7.33 cm or 2.89 inches
7.16 cm or 2.82 inches
6.38 cm or 2.51 inches