using motorshield gives a loud beeping noise

hi,

im Ian Jakubek and im new to arduino.
The problem i have is that when i run the code below on my arduino uno with arduino uno rev3 motorshield i get the motors to move but i also get a loud beeping noise.
this makes me worried, so can anyone help me with this.

the code:

/*************************************************************
Motor Shield 2-Channel DC Motor Demo
by Randy Sarafan

For more information see:
http://www.instructables.com/id/Arduino-Motor-Shield-Tutorial/

*************************************************************/

void setup() {
  
  //Setup Channel A
  pinMode(12, OUTPUT); //Initiates Motor Channel A pin
  pinMode(9, OUTPUT); //Initiates Brake Channel A pin

  //Setup Channel B
  pinMode(13, OUTPUT); //Initiates Motor Channel A pin
  pinMode(8, OUTPUT);  //Initiates Brake Channel A pin
  
}

void loop(){

  
  //Motor A forward @ full speed
  digitalWrite(12, HIGH); //Establishes forward direction of Channel A
  digitalWrite(9, LOW);   //Disengage the Brake for Channel A
  analogWrite(3, 255);   //Spins the motor on Channel A at full speed

  //Motor B backward @ half speed
  digitalWrite(13, HIGH);  //Establishes backward direction of Channel B
  digitalWrite(8, LOW);   //Disengage the Brake for Channel B
  analogWrite(11, 255);    //Spins the motor on Channel B at half speed

  delay(3600);
  
  digitalWrite(9, HIGH);  //Engage the Brake for Channel A
  digitalWrite(9, HIGH);  //Engage the Brake for Channel B
  
  
  delay(1000);
  
}

thx,
Ian Jakubek

What kind of motors are you using?

im using the motors from the ROBOT PLATFORM 2WD link:https://iprototype.be/products/robotics/platforms/robot-2wd

Getting "There is a problem with this website's security certificate." on the link.

dont worry about it, its an ssl error you can just skip it. if you really dont trust i can try to copy the html and place it on my own webhost.

Which component is the noise coming from ?
What is the period of the beep ?