int trigPin = 7;
int echoPin = 4;
int buzzerPin = 9; 
int ledPin = 6;
int time;		
int distance; 

void setup()
{
 pinMode(trigPin, OUTPUT); 
 pinMode(echoPin, INPUT); 
 pinMode (buzzerPin, OUTPUT); 
 pinMode(ledPin, OUTPUT);
}

void loop()
{
 digitalWrite(trigPin, HIGH);
 delayMicroseconds(5); 
 digitalWrite(trigPin, LOW); 
 int time = pulseIn(echoPin, HIGH); 
 int distance = (time*0.034)/2;  

 if (distance <= 100) {     
    tone(9, 900, 500);
    digitalWrite (buzzerPin, HIGH);
    digitalWrite(ledPin, HIGH);
    delay (500);
 }  
  
 if (distance <= 30) {     
    tone(9, 900, 100);
    digitalWrite (buzzerPin, HIGH);
    digitalWrite(ledPin, HIGH);
   	delay (100);
 } 
  
 else {                
    digitalWrite (buzzerPin, LOW);
    digitalWrite(ledPin, LOW);
    delay (200);  
 }
}