Beeping_Proximity_Sensor

const int trigPin = 9;
const int echoPin = 10;
int buzzpin=7;

long duration;
int distance;

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

void loop() 
{
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  
  digitalWrite(trigPin, LOW);
  
  duration = pulseIn(echoPin, HIGH);
  distance= duration*0.034/2;
  
 
  Serial.println(distance);
  
  delay(100);

  
 if(distance <= 40 && distance >30)
 {
 digitalWrite(buzzpin, HIGH);
   delay(2000);
   digitalWrite(buzzpin, LOW);
   delay(2000);
 }
 if(distance <= 30 && distance>20)
 {
 digitalWrite(buzzpin, HIGH);
   delay(500);
   digitalWrite(buzzpin, LOW);
   delay(500);
 }
  if(distance <= 20 && distance> 10)
 {
 digitalWrite(buzzpin, HIGH);
   delay(50);
   digitalWrite(buzzpin, LOW);
   delay(50);
 }
 if(distance <= 10)
 {
 digitalWrite(buzzpin, HIGH);
 }
 if(distance>40)
 {
 digitalWrite(buzzpin, LOW);
 }
}