The voice of a diver breathing in a mixture of oxygen and helium becomes higher-pitched. This is because helium is a lighter gas than nitrogen, which is the main component of air. When helium is inhaled, it travels faster through the vocal cords than nitrogen does. This causes the vocal cords to vibrate faster, which produces a higher-pitched voice.

The effect of helium on the voice is known as the Donald Duck effect, after the cartoon character who speaks with a high-pitched voice. The Donald Duck effect is a temporary effect that lasts only as long as the diver is breathing the helium mixture. Once the diver stops breathing the helium, the voice will return to its normal pitch.

The Donald Duck effect is a harmless phenomenon, but it can be fun to experience. It is a reminder that even slight changes in the environment can have a big impact on our bodies.