Ultrasonic sensor with buzzer

This is the code for an ultrasonic sensor with buzzer. Someone wanted to get code of two ultrasonic sensors, but unfortunately my other ultrasonic sensor broke so I could experiment with it.

The sketch

int greenled = 3; int redled = 4; int trigPin = 5; int echoPin = 6; void setup() {   Serial.begin (9600);   pinMode(trigPin, OUTPUT);   pinMode(echoPin, INPUT);     pinMode(greenled, OUTPUT);   pinMode(redled, OUTPUT); } void firstsensor(){ // This function is for first sensor.   int duration, distance;   digitalWrite (trigPin, HIGH);   delayMicroseconds (10);   digitalWrite (trigPin, LOW);   duration = pulseIn (echoPin, HIGH);   distance = (duration/2) / 29.1;       Serial.print("1st Sensor: ");       Serial.print(distance);       Serial.print("cm    ");   if (distance > 10) {  // Change the number for long or short distances.     digitalWrite (greenled, HIGH);       digitalWrite (redled, LOW); } else {      digitalWrite (greenled, LOW);      digitalWrite (redled, HIGH);    } } void loop() { Serial.println("\n"); firstsensor(); delay(100); }