void setup() {
pinMode(A0, INPUT);
pinMode(A1, INPUT);
pinMode(8, OUTPUT);
pinMode(A4, INPUT);
pinMode(A5, OUTPUT);
}
void loop() {
int val1 = 0;
int val2 = 0;
int val3 = 0;
int val4 = 0;
int val5 = 0;
int val6 = 0;
int val7 = 0;
int val8 = 0;
int val9 = 0;
int val10 = 0;
int sumval = 0;
int impuls = 120;   //select the pulse length depending on the frequency
int Delay = 0;  
int base = 0;
Delay = analogRead(A4);
pinMode(A0, OUTPUT);
digitalWrite(A0, LOW);
pinMode(A0, INPUT);
digitalWrite(8,HIGH);
delayMicroseconds(impuls);   
digitalWrite(8, LOW);
delayMicroseconds(Delay);      
val1 = analogRead(A0);
digitalWrite(8,HIGH);
delayMicroseconds(impuls);   
digitalWrite(8, LOW);
delayMicroseconds(Delay);    
val2 = analogRead(A0);
digitalWrite(8,HIGH);
delayMicroseconds(impuls);   
digitalWrite(8, LOW);
delayMicroseconds(Delay);    
val3 = analogRead(A0);
digitalWrite(8,HIGH);
delayMicroseconds(impuls);   
digitalWrite(8, LOW);
delayMicroseconds(Delay);   
val4 = analogRead(A0);
digitalWrite(8,HIGH);
delayMicroseconds(impuls);   
digitalWrite(8, LOW);
delayMicroseconds(Delay);   
val5 = analogRead(A0);
digitalWrite(8,HIGH);
delayMicroseconds(impuls);   
digitalWrite(8, LOW);
delayMicroseconds(Delay);   
val6 = analogRead(A0);
digitalWrite(8,HIGH);
delayMicroseconds(impuls);   
digitalWrite(8, LOW);
delayMicroseconds(Delay);   
val7 = analogRead(A0);
digitalWrite(8,HIGH);
delayMicroseconds(impuls);   
digitalWrite(8, LOW);
delayMicroseconds(Delay);   
val8 = analogRead(A0);
digitalWrite(8,HIGH);
delayMicroseconds(impuls);   
digitalWrite(8, LOW);
delayMicroseconds(Delay);   
val9 = analogRead(A0);
digitalWrite(8,HIGH);
delayMicroseconds(impuls);   
digitalWrite(8, LOW);
delayMicroseconds(Delay);   
val10 = analogRead(A0);
sumval = val1 + val2 + val3 + val4 + val5 + val6 + val7 + val8 + val9 + val10;
sumval = sumval/5;
base = analogRead(A1);
if (sumval > base)
{tone(A5,1000);
delay(50);
noTone(A5);
} 
else  {delay(50);
}
}