Geanine Edwards, age 9, of Colorado Springs, Colo., for her question:

WHY DOES THE VOICE CHANGE AS YOU GROW UP?

The pitch of your voice is determined by the size of your larynx. A woman's voice is usually pitched higher than a man's because her vocal cords are usually shorter.

Boys and girls usually have vocal cords about the same size until the boys reach puberty. Then the boys' voice boxes suddenly grow larger and their voices change to a lower pitch.

Teeth, lips and tongue also play a part in shaping the sound of your voice. The nasal cavity gives your voice color and resonance. If you happen to come down with a cold, your nasal passage will become stopped up and your voice will have a different quality.

Straining of your voice can affect your vocal cords and so can general muscular tension caused by nervousness.