Before a guys voice becomes lower during puberty his voice may break. Normally this starts to happen between 12 and 15 years, on average when a guy is 13,5.
Why does the voice crack?
In your throat is the larynx, also called the voice box, playing an important part in breathing, swallowing and talking. In the middle are the vocal cords.
During puberty the larynx of guys grows larger and it tilts to a different angle, making it stick out in the front of your neck. This lump is called the 'Adam’s apple.'
Because the larynx increases in size your vocal cords stretch. They become longer and thicker, making them vibrate at a lower frequency than before, which deepens the voice.
You don’t have a nice deep voice at once because the muscles around the vocal cords need time to adjust. During this period you may lack control over your voice. It may break, causing a squeaking sound. This may be embarrassing, but in most cases it doesn’t last very long.