* The size of the vocal cords. The longer the vocal cords, the lower the pitch of the voice. Men typically have longer vocal cords than women, which is why they generally have deeper voices.
* The thickness of the vocal cords. The thicker the vocal cords, the lower the pitch of the voice. This is because thicker vocal cords vibrate more slowly.
* The shape of the vocal tract. The shape of the vocal tract can also affect the pitch of the voice. A longer vocal tract will produce a lower pitch than a shorter vocal tract.
* The amount of testosterone in the body. Testosterone is a hormone that is produced in greater amounts in men than in women. Testosterone can cause the vocal cords to thicken and lengthen, which can lead to a deeper voice.
It is important to note that not all men have deep voices and not all women have high voices. There is a lot of variation in voice pitch, and there is no one "normal" voice.