While at an amusement park, you inhale helium from a balloon to make your voice higher pitched. A friend says that helium reacts with and tightens the vocal cords to make your voice have the higher pitch. Could he be correct? Why or why not?

Sound pitch is a key aspect of the auditory experiences we encounter daily, especially in communication. It refers to how high or low we perceive a sound to be. This quality of sound is directly related to the frequency of the sound waves, which are the number of vibrations per second. The unit of frequency is Hertz (Hz), where one Hz equates to one vibration per second.

Higher frequency sound waves produce a higher pitch, whereas lower frequency waves result in a lower pitch. Musical notes are a classic example of sound pitches varying in frequency. When someone sings notes varying from bass to soprano, they are effectively changing the frequency of their vocal cord vibrations to adjust the pitch of their voice. In the context of the amusement park scenario, inhaling helium doesn't increase the frequency of the vocal cord vibrations; instead, it changes the properties of the medium around the vocal cords, leading to a perceived higher pitch.

The vocal cords are an essential element of our speech system, nestled within the larynx, or voice box. Their primary function is to produce sound when air expelled from the lungs passes through them, causing them to vibrate.

This vibration is finely controlled by various muscles, which can tighten or loosen the vocal cords to change the pitch of the sound produced. When the vocal cords are tight, they vibrate at a higher frequency, creating a higher-pitched sound. Conversely, loosened vocal cords vibrate slower, resulting in a lower pitch. Breath control and vocal chord coordination allow us to articulate different sounds and modulate our voice pitch as desired during speech or singing.

Helium, the second lightest and second most abundant element in the observable universe, possesses unique properties that play a fascinating role in altering the sound of a voice when inhaled.

One crucial property is its low density compared to air. This low density affects how sound travels through it. Helium is also inert, meaning it does not react chemically with the tissues of the body, including the vocal cords. In the whimsical act of speaking with a voice affected by helium, the gas's properties create a change in how the sound is propagated, but without any chemical reaction or physical alteration to our vocal cords themselves.

The speed at which sound waves travel is not constant. It varies depending on the medium they pass through. Sound travels by causing particles in a medium to vibrate and transfer energy from one particle to the next.

In general, sound travels faster in denser mediums, such as solids, and slower in less dense mediums, such as gases. However, when comparing gases, the speed of sound is higher in lighter gases like helium, which has faster-moving particles due for its lower density than it is in heavier gases like air. This counterintuitive phenomenon is the precise reason our voices sound higher-pitched when we inhale helium: the sound of our voice, travelling faster due to the medium of helium, reaches the listener's ear at a higher frequency.