const int trigPin = 9;
const int echoPin = 10;
const int buzzerPin = 8;
long duration;
int distance;

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

        void loop() {
          // Clears the trigPin by setting it LOW for 2 microseconds
            digitalWrite(trigPin, LOW);
              delayMicroseconds(2);

                // Sets the trigPin on HIGH state for 10 microseconds
                  digitalWrite(trigPin, HIGH);
                    delayMicroseconds(10);
                      digitalWrite(trigPin, LOW);

                        // Reads the echoPin, returns the sound wave travel time in microseconds
                          duration = pulseIn(echoPin, HIGH);

                            // Calculating the distance
                              distance = duration * 0.034 / 2;
                                Serial.print("Distance: ");
                                  Serial.print(distance);
                                    Serial.println(" cm");

                                      // If the distance is less than 30 cm, beep the buzzer
                                        if (distance < 100) {
                                          
                                            tone(buzzerPin, 1000);
                                              } else {
                                                  noTone(buzzerPin);
                                                    }

                                                       delay(50);
          }