Why does a boy’s voice usually deepen during puberty?

During puberty, a boy’s voice deepens primarily due to the influence of sex hormones, specifically testosterone.12

These hormonal changes stimulate the growth and enlargement of the larynx, or voice box. As the larynx grows, the vocal cords housed within it become longer and thicker. Because the pitch of a person’s voice is determined by the size of the larynx and the dimensions of the vocal cords, these structural changes result in a lower vocal pitch.132

Additionally, the growth of the larynx causes the thyroid cartilage to expand and push outward, which creates the visible prominence in the neck known as the Adam’s apple. While these changes occur in all humans to some degree, they are typically more pronounced in males due to the specific hormonal activity during this developmental stage.412