user70077: I am new to Arduino and just got this error after writing this code:The error message is pasted after the code. I am kindly requesting for assistance so that someone can help me understand why it isn't compiling. I even changed the board to mega at the tools section but still get the same error

    #include <Tone.h>

int ledred1 = 2;
int ledgreen1 = 3;
int ledorange1 = 4;
int ledred2 = 5;
int ledgreen2 = 6;
int ledorange2 = 7;
int ledred3 = 8;
int ledgreen3 = 9;
int ledorange3 = 10;

int sound = 250;

int trigPin1 = 11;
int echoPin1 = 12;

int trigPin2 = 13;
int echoPin2 = 14;

int trigPin3 = 15;
int echoPin3 = 16;

#define buzzer1 17
#define buzzer2 18
#define buzzer3 19

Tone tone1;
Tone tone2;
Tone tone3;

long distance1=0; 
long distance2=0;
long distance3=0; 

long t1=-10000;
long t2=-10000;
long t3=-10000;

void checkDistance(long distance, Tone toneobj, int frequency, long *timer);

long measure(int trigger, int echo);


void setup() {
  Serial.begin (9600);
  pinMode(trigPin1, OUTPUT);
  pinMode(echoPin1, INPUT);
 
  pinMode(trigPin2, OUTPUT);
  pinMode(echoPin2, INPUT);
 
  pinMode(trigPin3, OUTPUT);
  pinMode(echoPin3, INPUT);

  tone1.begin(buzzer1);
  tone2.begin(buzzer2);
  tone3.begin(buzzer3);
 
  pinMode(ledred1, OUTPUT);
  pinMode(ledred2, OUTPUT);
  pinMode(ledgreen1, OUTPUT);
  pinMode(ledgreen2, OUTPUT);
  pinMode(ledred3, OUTPUT);
  pinMode(ledgreen3, OUTPUT);
}
void firstsensor(){ // This function is for first sensor. 
  int duration1, distance1;
  digitalWrite (trigPin1, HIGH);
  delayMicroseconds (10);
  digitalWrite (trigPin1, LOW);
  duration1 = pulseIn (echoPin1, HIGH);
  distance1 = (duration1/2) / 29.1;

      Serial.print("1st Sensor: ");
      Serial.print(distance1); 
      Serial.print("cm    ");

  if (distance1 <=200&& distance1>=100) {  // Change the number for long or short distances.
    digitalWrite (ledred1, LOW);
    digitalWrite (ledgreen1,HIGH);
    digitalWrite (ledorange1,LOW);
    digitalWrite (ledred2, LOW);
    digitalWrite (ledorange2,LOW);
    digitalWrite (ledgreen2, LOW);
    digitalWrite (ledred3, LOW);
    digitalWrite (ledorange3,LOW);
    digitalWrite (ledgreen3, LOW);
    
    sound=250;

  } else {
    digitalWrite (ledred1, LOW);
    digitalWrite (ledgreen1,LOW);
    digitalWrite (ledorange1,LOW);
    digitalWrite (ledred2, LOW);
    digitalWrite (ledorange2,LOW);
    digitalWrite (ledgreen2, LOW);
    digitalWrite (ledred3, LOW);
    digitalWrite (ledorange3,LOW);
    digitalWrite (ledgreen3, LOW);
     }   


  if (distance1 <100&& distance1>=50) {  // Change the number for long or short distances.
    digitalWrite (ledred1, LOW);
    digitalWrite (ledgreen1,LOW);
    digitalWrite (ledorange1,HIGH);
    digitalWrite (ledred2, LOW);
    digitalWrite (ledorange2,LOW);
    digitalWrite (ledgreen2, LOW);
    digitalWrite (ledred3, LOW);
    digitalWrite (ledorange3,LOW);
    digitalWrite (ledgreen3, LOW);
    
    sound=275;

  } else {
    digitalWrite (ledred1, LOW);
    digitalWrite (ledgreen1,LOW);
    digitalWrite (ledorange1,LOW);
    digitalWrite (ledred2, LOW);
    digitalWrite (ledorange2,LOW);
    digitalWrite (ledgreen2, LOW);
    digitalWrite (ledred3, LOW);
    digitalWrite (ledorange3,LOW);
    digitalWrite (ledgreen3, LOW);
      }   
        if (distance1 <50&& distance1>=0) {  // Change the number for long or short distances.
    digitalWrite (ledred1, HIGH);
    digitalWrite (ledgreen1,LOW);
    digitalWrite (ledorange1,LOW);
    digitalWrite (ledred2, LOW);
    digitalWrite (ledorange2,LOW);
    digitalWrite (ledgreen2, LOW);
    digitalWrite (ledred3, LOW);
    digitalWrite (ledorange3,LOW);
    digitalWrite (ledgreen3, LOW);
    
    sound=300;

  } else {
    digitalWrite (ledred1, LOW);
    digitalWrite (ledgreen1,LOW);
    digitalWrite (ledorange1,LOW);
    digitalWrite (ledred2, LOW);
    digitalWrite (ledorange2,LOW);
    digitalWrite (ledgreen2, LOW);
    digitalWrite (ledred3, LOW);
    digitalWrite (ledorange3,LOW);
    digitalWrite (ledgreen3, LOW);
      } 
      if(distance1>200 || distance1<0){
    Serial.println("Out of Range");
    noTone(buzzer1);
  }
  else{
    Serial.print(distance1);
    Serial.println("cm");
    tone(buzzer1,sound);

  }  
}
void secondsensor(){ // This function is for second sensor.
    int duration2, distance2;
    digitalWrite (trigPin2, HIGH);
    delayMicroseconds (10);
    digitalWrite (trigPin2, LOW);
    duration2 = pulseIn (echoPin2, HIGH);
    distance2 = (duration2/2) / 29.1;
 
      Serial.print("2nd Sensor: ");
      Serial.print(distance2); 
      Serial.print("cm    ");
  
     if (distance2 <=200&& distance2>=100) {  // Change the number for long or short distances.
    digitalWrite (ledred1, LOW);
    digitalWrite (ledgreen1,LOW);
    digitalWrite (ledorange1,LOW);
    digitalWrite (ledred2, LOW);
    digitalWrite (ledorange2,LOW);
    digitalWrite (ledgreen2, HIGH);
    digitalWrite (ledred3, LOW);
    digitalWrite (ledorange3,LOW);
    digitalWrite (ledgreen3, LOW);
    
    sound=250;

  } else {
    digitalWrite (ledred1, LOW);
    digitalWrite (ledgreen1,LOW);
    digitalWrite (ledorange1,LOW);
    digitalWrite (ledred2, LOW);
    digitalWrite (ledorange2,LOW);
    digitalWrite (ledgreen2, LOW);
    digitalWrite (ledred3, LOW);
    digitalWrite (ledorange3,LOW);
    digitalWrite (ledgreen3, LOW);
     }   


  if (distance2 <100&& distance2>=50) {  // Change the number for long or short distances.
    digitalWrite (ledred1, LOW);
    digitalWrite (ledgreen1,LOW);
    digitalWrite (ledorange1,LOW);
    digitalWrite (ledred2, LOW);
    digitalWrite (ledorange2,HIGH);
    digitalWrite (ledgreen2, LOW);
    digitalWrite (ledred3, LOW);
    digitalWrite (ledorange3,LOW);
    digitalWrite (ledgreen3, LOW);
    
    sound=275;

  } else {
    digitalWrite (ledred1, LOW);
    digitalWrite (ledgreen1,LOW);
    digitalWrite (ledorange1,LOW);
    digitalWrite (ledred2, LOW);
    digitalWrite (ledorange2,LOW);
    digitalWrite (ledgreen2, LOW);
    digitalWrite (ledred3, LOW);
    digitalWrite (ledorange3,LOW);
    digitalWrite (ledgreen3, LOW);
      }   
        if (distance2 <50&& distance2>=0) {  // Change the number for long or short distances.
    digitalWrite (ledred1, LOW);
    digitalWrite (ledgreen1,LOW);
    digitalWrite (ledorange1,LOW);
    digitalWrite (ledred2, HIGH);
    digitalWrite (ledorange2,LOW);
    digitalWrite (ledgreen2, LOW);
    digitalWrite (ledred3, LOW);
    digitalWrite (ledorange3,LOW);
    digitalWrite (ledgreen3, LOW);
    
    sound=300;

  } else {
    digitalWrite (ledred1, LOW);
    digitalWrite (ledgreen1,LOW);
    digitalWrite (ledorange1,LOW);
    digitalWrite (ledred2, LOW);
    digitalWrite (ledorange2,LOW);
    digitalWrite (ledgreen2, LOW);
    digitalWrite (ledred3, LOW);
    digitalWrite (ledorange3,LOW);
    digitalWrite (ledgreen3, LOW);
      } 
      if(distance2>200 || distance2<0){
    Serial.println("Out of Range");
    noTone(buzzer2);
  }
  else{
    Serial.print(distance2);
    Serial.println("cm");
    tone(buzzer2,sound);

  }  
}
void thirdsensor(){ // This function is for third sensor.
    int duration3, distance3;
    digitalWrite (trigPin3, HIGH);
    delayMicroseconds (10);
    digitalWrite (trigPin3, LOW);
    duration3 = pulseIn (echoPin3, HIGH);
    distance3 = (duration3/2) / 29.1;

      Serial.print("3rd Sensor: ");  
      Serial.print(distance3); 
      Serial.print("cm");
  
     if (distance3 <=200&& distance3>=100) {  // Change the number for long or short distances.
    digitalWrite (ledred1, LOW);
    digitalWrite (ledgreen1,LOW);
    digitalWrite (ledorange1,LOW);
    digitalWrite (ledred2, LOW);
    digitalWrite (ledorange2,LOW);
    digitalWrite (ledgreen2, LOW);
    digitalWrite (ledred3, LOW);
    digitalWrite (ledorange3,LOW);
    digitalWrite (ledgreen3, HIGH);
    
    sound=250;

  } else {
    digitalWrite (ledred1, LOW);
    digitalWrite (ledgreen1,LOW);
    digitalWrite (ledorange1,LOW);
    digitalWrite (ledred2, LOW);
    digitalWrite (ledorange2,LOW);
    digitalWrite (ledgreen2, LOW);
    digitalWrite (ledred3, LOW);
    digitalWrite (ledorange3,LOW);
    digitalWrite (ledgreen3, LOW);
     }   


  if (distance3 <100&& distance3>=50) {  // Change the number for long or short distances.
    digitalWrite (ledred1, LOW);
    digitalWrite (ledgreen1,LOW);
    digitalWrite (ledorange1,LOW);
    digitalWrite (ledred2, LOW);
    digitalWrite (ledorange2,LOW);
    digitalWrite (ledgreen2, LOW);
    digitalWrite (ledred3, LOW);
    digitalWrite (ledorange3,HIGH);
    digitalWrite (ledgreen3, LOW);
    
    sound=275;

  } else {
    digitalWrite (ledred1, LOW);
    digitalWrite (ledgreen1,LOW);
    digitalWrite (ledorange1,LOW);
    digitalWrite (ledred2, LOW);
    digitalWrite (ledorange2,LOW);
    digitalWrite (ledgreen2, LOW);
    digitalWrite (ledred3, LOW);
    digitalWrite (ledorange3,LOW);
    digitalWrite (ledgreen3, LOW);
      }   
        if (distance1 <50&& distance1>=0) {  // Change the number for long or short distances.
    digitalWrite (ledred1, LOW);
    digitalWrite (ledgreen1,LOW);
    digitalWrite (ledorange1,LOW);
    digitalWrite (ledred2, LOW);
    digitalWrite (ledorange2,LOW);
    digitalWrite (ledgreen2, LOW);
    digitalWrite (ledred3, LOW);
    digitalWrite (ledorange3,LOW);
    digitalWrite (ledgreen3, LOW);
    
    sound=300;

  } else {
    digitalWrite (ledred1, LOW);
    digitalWrite (ledgreen1,LOW);
    digitalWrite (ledorange1,LOW);
    digitalWrite (ledred2, LOW);
    digitalWrite (ledorange2,LOW);
    digitalWrite (ledgreen2, LOW);
    digitalWrite (ledred3, LOW);
    digitalWrite (ledorange3,LOW);
    digitalWrite (ledgreen3, LOW);
      } 
      if(distance3>200 || distance3<0){
    Serial.println("Out of Range");
    noTone(buzzer3);
  }
  else{
    Serial.print(distance3);
    Serial.println("cm");
    tone(buzzer3,sound);

  }  
}

void loop() {
Serial.println("\n");
firstsensor();
secondsensor();
thirdsensor();
delay(100);
}

This is the error message:
Arduino: 1.8.13 (Linux), Board: "Arduino Uno"
Tone.cpp.o (symbol from plugin): In function `timer0_pin_port':
(.text+0x0): multiple definition of `timer0_pin_port'
libraries/Tone-1.0.0/Tone.cpp.o (symbol from plugin):(.text+0x0): first defined here
Tone.cpp.o (symbol from plugin): In function `timer0_pin_port':
(.text+0x0): multiple definition of `timer0_pin_mask'
libraries/Tone-1.0.0/Tone.cpp.o (symbol from plugin):(.text+0x0): first defined here
Tone.cpp.o (symbol from plugin): In function `timer0_pin_port':
(.text+0x0): multiple definition of `timer1_pin_port'
libraries/Tone-1.0.0/Tone.cpp.o (symbol from plugin):(.text+0x0): first defined here
Tone.cpp.o (symbol from plugin): In function `timer0_pin_port':
(.text+0x0): multiple definition of `timer1_pin_mask'
libraries/Tone-1.0.0/Tone.cpp.o (symbol from plugin):(.text+0x0): first defined here
Tone.cpp.o (symbol from plugin): In function `timer0_pin_port':
(.text+0x0): multiple definition of `timer2_pin_port'
libraries/Tone-1.0.0/Tone.cpp.o (symbol from plugin):(.text+0x0): first defined here
Tone.cpp.o (symbol from plugin): In function `timer0_pin_port':
(.text+0x0): multiple definition of `timer2_pin_mask'
libraries/Tone-1.0.0/Tone.cpp.o (symbol from plugin):(.text+0x0): first defined here
Tone.cpp.o (symbol from plugin): In function `timer0_pin_port':
(.text+0x0): multiple definition of `timer0_toggle_count'
libraries/Tone-1.0.0/Tone.cpp.o (symbol from plugin):(.text+0x0): first defined here
Tone.cpp.o (symbol from plugin): In function `timer0_pin_port':
(.text+0x0): multiple definition of `timer1_toggle_count'
libraries/Tone-1.0.0/Tone.cpp.o (symbol from plugin):(.text+0x0): first defined here
Tone.cpp.o (symbol from plugin): In function `timer0_pin_port':
(.text+0x0): multiple definition of `timer2_toggle_count'
libraries/Tone-1.0.0/Tone.cpp.o (symbol from plugin):(.text+0x0): first defined here
Tone.cpp.o (symbol from plugin): In function `timer0_pin_port':
(.text+0x0): multiple definition of `__vector_7'
libraries/Tone-1.0.0/Tone.cpp.o (symbol from plugin):(.text+0x0): first defined here
collect2: error: ld returned 1 exit status
exit status 1
Error compiling for board Arduino Uno.


This report would have more information with
"Show verbose output during compilation"
option enabled in File -> Preferences.


user37622: You include the Tone library and you use the tone() function from core. They are in conflict.
Use tone1.tone() or remove the Tone library and use the tone() function.

70077: <p>I am new to Arduino and just got this error after writing this code:The error message is pasted after the code. I am kindly requesting for assistance so that someone can help me understand why it isn't compiling. I even changed the board to mega at the tools section but still get the same error</p>
<pre class="lang-cpp prettyprint-override"><code>
    #include &lt;Tone.h&gt;

int ledred1 = 2;
int ledgreen1 = 3;
int ledorange1 = 4;
int ledred2 = 5;
int ledgreen2 = 6;
int ledorange2 = 7;
int ledred3 = 8;
int ledgreen3 = 9;
int ledorange3 = 10;

int sound = 250;

int trigPin1 = 11;
int echoPin1 = 12;

int trigPin2 = 13;
int echoPin2 = 14;

int trigPin3 = 15;
int echoPin3 = 16;

#define buzzer1 17
#define buzzer2 18
#define buzzer3 19

Tone tone1;
Tone tone2;
Tone tone3;

long distance1=0; 
long distance2=0;
long distance3=0; 

long t1=-10000;
long t2=-10000;
long t3=-10000;

void checkDistance(long distance, Tone toneobj, int frequency, long *timer);

long measure(int trigger, int echo);


void setup() {
  Serial.begin (9600);
  pinMode(trigPin1, OUTPUT);
  pinMode(echoPin1, INPUT);
 
  pinMode(trigPin2, OUTPUT);
  pinMode(echoPin2, INPUT);
 
  pinMode(trigPin3, OUTPUT);
  pinMode(echoPin3, INPUT);

  tone1.begin(buzzer1);
  tone2.begin(buzzer2);
  tone3.begin(buzzer3);
 
  pinMode(ledred1, OUTPUT);
  pinMode(ledred2, OUTPUT);
  pinMode(ledgreen1, OUTPUT);
  pinMode(ledgreen2, OUTPUT);
  pinMode(ledred3, OUTPUT);
  pinMode(ledgreen3, OUTPUT);
}
void firstsensor(){ // This function is for first sensor. 
  int duration1, distance1;
  digitalWrite (trigPin1, HIGH);
  delayMicroseconds (10);
  digitalWrite (trigPin1, LOW);
  duration1 = pulseIn (echoPin1, HIGH);
  distance1 = (duration1/2) / 29.1;

      Serial.print(&quot;1st Sensor: &quot;);
      Serial.print(distance1); 
      Serial.print(&quot;cm    &quot;);

  if (distance1 &lt;=200&amp;&amp; distance1&gt;=100) {  // Change the number for long or short distances.
    digitalWrite (ledred1, LOW);
    digitalWrite (ledgreen1,HIGH);
    digitalWrite (ledorange1,LOW);
    digitalWrite (ledred2, LOW);
    digitalWrite (ledorange2,LOW);
    digitalWrite (ledgreen2, LOW);
    digitalWrite (ledred3, LOW);
    digitalWrite (ledorange3,LOW);
    digitalWrite (ledgreen3, LOW);
    
    sound=250;

  } else {
    digitalWrite (ledred1, LOW);
    digitalWrite (ledgreen1,LOW);
    digitalWrite (ledorange1,LOW);
    digitalWrite (ledred2, LOW);
    digitalWrite (ledorange2,LOW);
    digitalWrite (ledgreen2, LOW);
    digitalWrite (ledred3, LOW);
    digitalWrite (ledorange3,LOW);
    digitalWrite (ledgreen3, LOW);
     }   


  if (distance1 &lt;100&amp;&amp; distance1&gt;=50) {  // Change the number for long or short distances.
    digitalWrite (ledred1, LOW);
    digitalWrite (ledgreen1,LOW);
    digitalWrite (ledorange1,HIGH);
    digitalWrite (ledred2, LOW);
    digitalWrite (ledorange2,LOW);
    digitalWrite (ledgreen2, LOW);
    digitalWrite (ledred3, LOW);
    digitalWrite (ledorange3,LOW);
    digitalWrite (ledgreen3, LOW);
    
    sound=275;

  } else {
    digitalWrite (ledred1, LOW);
    digitalWrite (ledgreen1,LOW);
    digitalWrite (ledorange1,LOW);
    digitalWrite (ledred2, LOW);
    digitalWrite (ledorange2,LOW);
    digitalWrite (ledgreen2, LOW);
    digitalWrite (ledred3, LOW);
    digitalWrite (ledorange3,LOW);
    digitalWrite (ledgreen3, LOW);
      }   
        if (distance1 &lt;50&amp;&amp; distance1&gt;=0) {  // Change the number for long or short distances.
    digitalWrite (ledred1, HIGH);
    digitalWrite (ledgreen1,LOW);
    digitalWrite (ledorange1,LOW);
    digitalWrite (ledred2, LOW);
    digitalWrite (ledorange2,LOW);
    digitalWrite (ledgreen2, LOW);
    digitalWrite (ledred3, LOW);
    digitalWrite (ledorange3,LOW);
    digitalWrite (ledgreen3, LOW);
    
    sound=300;

  } else {
    digitalWrite (ledred1, LOW);
    digitalWrite (ledgreen1,LOW);
    digitalWrite (ledorange1,LOW);
    digitalWrite (ledred2, LOW);
    digitalWrite (ledorange2,LOW);
    digitalWrite (ledgreen2, LOW);
    digitalWrite (ledred3, LOW);
    digitalWrite (ledorange3,LOW);
    digitalWrite (ledgreen3, LOW);
      } 
      if(distance1&gt;200 || distance1&lt;0){
    Serial.println(&quot;Out of Range&quot;);
    noTone(buzzer1);
  }
  else{
    Serial.print(distance1);
    Serial.println(&quot;cm&quot;);
    tone(buzzer1,sound);

  }  
}
void secondsensor(){ // This function is for second sensor.
    int duration2, distance2;
    digitalWrite (trigPin2, HIGH);
    delayMicroseconds (10);
    digitalWrite (trigPin2, LOW);
    duration2 = pulseIn (echoPin2, HIGH);
    distance2 = (duration2/2) / 29.1;
 
      Serial.print(&quot;2nd Sensor: &quot;);
      Serial.print(distance2); 
      Serial.print(&quot;cm    &quot;);
  
     if (distance2 &lt;=200&amp;&amp; distance2&gt;=100) {  // Change the number for long or short distances.
    digitalWrite (ledred1, LOW);
    digitalWrite (ledgreen1,LOW);
    digitalWrite (ledorange1,LOW);
    digitalWrite (ledred2, LOW);
    digitalWrite (ledorange2,LOW);
    digitalWrite (ledgreen2, HIGH);
    digitalWrite (ledred3, LOW);
    digitalWrite (ledorange3,LOW);
    digitalWrite (ledgreen3, LOW);
    
    sound=250;

  } else {
    digitalWrite (ledred1, LOW);
    digitalWrite (ledgreen1,LOW);
    digitalWrite (ledorange1,LOW);
    digitalWrite (ledred2, LOW);
    digitalWrite (ledorange2,LOW);
    digitalWrite (ledgreen2, LOW);
    digitalWrite (ledred3, LOW);
    digitalWrite (ledorange3,LOW);
    digitalWrite (ledgreen3, LOW);
     }   


  if (distance2 &lt;100&amp;&amp; distance2&gt;=50) {  // Change the number for long or short distances.
    digitalWrite (ledred1, LOW);
    digitalWrite (ledgreen1,LOW);
    digitalWrite (ledorange1,LOW);
    digitalWrite (ledred2, LOW);
    digitalWrite (ledorange2,HIGH);
    digitalWrite (ledgreen2, LOW);
    digitalWrite (ledred3, LOW);
    digitalWrite (ledorange3,LOW);
    digitalWrite (ledgreen3, LOW);
    
    sound=275;

  } else {
    digitalWrite (ledred1, LOW);
    digitalWrite (ledgreen1,LOW);
    digitalWrite (ledorange1,LOW);
    digitalWrite (ledred2, LOW);
    digitalWrite (ledorange2,LOW);
    digitalWrite (ledgreen2, LOW);
    digitalWrite (ledred3, LOW);
    digitalWrite (ledorange3,LOW);
    digitalWrite (ledgreen3, LOW);
      }   
        if (distance2 &lt;50&amp;&amp; distance2&gt;=0) {  // Change the number for long or short distances.
    digitalWrite (ledred1, LOW);
    digitalWrite (ledgreen1,LOW);
    digitalWrite (ledorange1,LOW);
    digitalWrite (ledred2, HIGH);
    digitalWrite (ledorange2,LOW);
    digitalWrite (ledgreen2, LOW);
    digitalWrite (ledred3, LOW);
    digitalWrite (ledorange3,LOW);
    digitalWrite (ledgreen3, LOW);
    
    sound=300;

  } else {
    digitalWrite (ledred1, LOW);
    digitalWrite (ledgreen1,LOW);
    digitalWrite (ledorange1,LOW);
    digitalWrite (ledred2, LOW);
    digitalWrite (ledorange2,LOW);
    digitalWrite (ledgreen2, LOW);
    digitalWrite (ledred3, LOW);
    digitalWrite (ledorange3,LOW);
    digitalWrite (ledgreen3, LOW);
      } 
      if(distance2&gt;200 || distance2&lt;0){
    Serial.println(&quot;Out of Range&quot;);
    noTone(buzzer2);
  }
  else{
    Serial.print(distance2);
    Serial.println(&quot;cm&quot;);
    tone(buzzer2,sound);

  }  
}
void thirdsensor(){ // This function is for third sensor.
    int duration3, distance3;
    digitalWrite (trigPin3, HIGH);
    delayMicroseconds (10);
    digitalWrite (trigPin3, LOW);
    duration3 = pulseIn (echoPin3, HIGH);
    distance3 = (duration3/2) / 29.1;

      Serial.print(&quot;3rd Sensor: &quot;);  
      Serial.print(distance3); 
      Serial.print(&quot;cm&quot;);
  
     if (distance3 &lt;=200&amp;&amp; distance3&gt;=100) {  // Change the number for long or short distances.
    digitalWrite (ledred1, LOW);
    digitalWrite (ledgreen1,LOW);
    digitalWrite (ledorange1,LOW);
    digitalWrite (ledred2, LOW);
    digitalWrite (ledorange2,LOW);
    digitalWrite (ledgreen2, LOW);
    digitalWrite (ledred3, LOW);
    digitalWrite (ledorange3,LOW);
    digitalWrite (ledgreen3, HIGH);
    
    sound=250;

  } else {
    digitalWrite (ledred1, LOW);
    digitalWrite (ledgreen1,LOW);
    digitalWrite (ledorange1,LOW);
    digitalWrite (ledred2, LOW);
    digitalWrite (ledorange2,LOW);
    digitalWrite (ledgreen2, LOW);
    digitalWrite (ledred3, LOW);
    digitalWrite (ledorange3,LOW);
    digitalWrite (ledgreen3, LOW);
     }   


  if (distance3 &lt;100&amp;&amp; distance3&gt;=50) {  // Change the number for long or short distances.
    digitalWrite (ledred1, LOW);
    digitalWrite (ledgreen1,LOW);
    digitalWrite (ledorange1,LOW);
    digitalWrite (ledred2, LOW);
    digitalWrite (ledorange2,LOW);
    digitalWrite (ledgreen2, LOW);
    digitalWrite (ledred3, LOW);
    digitalWrite (ledorange3,HIGH);
    digitalWrite (ledgreen3, LOW);
    
    sound=275;

  } else {
    digitalWrite (ledred1, LOW);
    digitalWrite (ledgreen1,LOW);
    digitalWrite (ledorange1,LOW);
    digitalWrite (ledred2, LOW);
    digitalWrite (ledorange2,LOW);
    digitalWrite (ledgreen2, LOW);
    digitalWrite (ledred3, LOW);
    digitalWrite (ledorange3,LOW);
    digitalWrite (ledgreen3, LOW);
      }   
        if (distance1 &lt;50&amp;&amp; distance1&gt;=0) {  // Change the number for long or short distances.
    digitalWrite (ledred1, LOW);
    digitalWrite (ledgreen1,LOW);
    digitalWrite (ledorange1,LOW);
    digitalWrite (ledred2, LOW);
    digitalWrite (ledorange2,LOW);
    digitalWrite (ledgreen2, LOW);
    digitalWrite (ledred3, LOW);
    digitalWrite (ledorange3,LOW);
    digitalWrite (ledgreen3, LOW);
    
    sound=300;

  } else {
    digitalWrite (ledred1, LOW);
    digitalWrite (ledgreen1,LOW);
    digitalWrite (ledorange1,LOW);
    digitalWrite (ledred2, LOW);
    digitalWrite (ledorange2,LOW);
    digitalWrite (ledgreen2, LOW);
    digitalWrite (ledred3, LOW);
    digitalWrite (ledorange3,LOW);
    digitalWrite (ledgreen3, LOW);
      } 
      if(distance3&gt;200 || distance3&lt;0){
    Serial.println(&quot;Out of Range&quot;);
    noTone(buzzer3);
  }
  else{
    Serial.print(distance3);
    Serial.println(&quot;cm&quot;);
    tone(buzzer3,sound);

  }  
}

void loop() {
Serial.println(&quot;\n&quot;);
firstsensor();
secondsensor();
thirdsensor();
delay(100);
}
</code></pre>
<p>This is the error message:
Arduino: 1.8.13 (Linux), Board: &quot;Arduino Uno&quot;</p>
<pre><code>Tone.cpp.o (symbol from plugin): In function `timer0_pin_port':
(.text+0x0): multiple definition of `timer0_pin_port'
libraries/Tone-1.0.0/Tone.cpp.o (symbol from plugin):(.text+0x0): first defined here
Tone.cpp.o (symbol from plugin): In function `timer0_pin_port':
(.text+0x0): multiple definition of `timer0_pin_mask'
libraries/Tone-1.0.0/Tone.cpp.o (symbol from plugin):(.text+0x0): first defined here
Tone.cpp.o (symbol from plugin): In function `timer0_pin_port':
(.text+0x0): multiple definition of `timer1_pin_port'
libraries/Tone-1.0.0/Tone.cpp.o (symbol from plugin):(.text+0x0): first defined here
Tone.cpp.o (symbol from plugin): In function `timer0_pin_port':
(.text+0x0): multiple definition of `timer1_pin_mask'
libraries/Tone-1.0.0/Tone.cpp.o (symbol from plugin):(.text+0x0): first defined here
Tone.cpp.o (symbol from plugin): In function `timer0_pin_port':
(.text+0x0): multiple definition of `timer2_pin_port'
libraries/Tone-1.0.0/Tone.cpp.o (symbol from plugin):(.text+0x0): first defined here
Tone.cpp.o (symbol from plugin): In function `timer0_pin_port':
(.text+0x0): multiple definition of `timer2_pin_mask'
libraries/Tone-1.0.0/Tone.cpp.o (symbol from plugin):(.text+0x0): first defined here
Tone.cpp.o (symbol from plugin): In function `timer0_pin_port':
(.text+0x0): multiple definition of `timer0_toggle_count'
libraries/Tone-1.0.0/Tone.cpp.o (symbol from plugin):(.text+0x0): first defined here
Tone.cpp.o (symbol from plugin): In function `timer0_pin_port':
(.text+0x0): multiple definition of `timer1_toggle_count'
libraries/Tone-1.0.0/Tone.cpp.o (symbol from plugin):(.text+0x0): first defined here
Tone.cpp.o (symbol from plugin): In function `timer0_pin_port':
(.text+0x0): multiple definition of `timer2_toggle_count'
libraries/Tone-1.0.0/Tone.cpp.o (symbol from plugin):(.text+0x0): first defined here
Tone.cpp.o (symbol from plugin): In function `timer0_pin_port':
(.text+0x0): multiple definition of `__vector_7'
libraries/Tone-1.0.0/Tone.cpp.o (symbol from plugin):(.text+0x0): first defined here
collect2: error: ld returned 1 exit status
exit status 1
Error compiling for board Arduino Uno.


This report would have more information with
&quot;Show verbose output during compilation&quot;
option enabled in File -&gt; Preferences.
</code></pre>
 37622: <p>You include the Tone library and you use the <code>tone()</code> function from core. They are in conflict.</p>
<p>Use <code>tone1.tone()</code> or remove the Tone library and use the <code>tone()</code> function.</p>
