Speaking

• Speaking requires air to move from your lungs, through your vocal cords and out your mouth. Manipulating the shape of your lips, tongue and soft palate creates specific words and sounds. The air moving through the throat vibrates the vocal cords as it passes through, creating sound in the form of resonance frequencies. Speech elements each have a specific resonance frequency that is the same for everyone, regardless of the timbre of their voice. The sound SH is recognized as the same from a three-year old child or from an adult. This consistency in resonance frequencies allows the recognition of words in speech. Resonance frequency vibrations do not change when helium is inhaled, rather the composition of the gases in your throat changes.
  
  

Timbre

• The vibrations in the air inside your throat are referred to as timbre. Timbre allows you to distinguish between the same sounds at the same volume from two different sources. A musician can recognize a middle C played on a saxophone, flute or clarinet. Changes in the timbre of the voice create a change in the sound after inhaling helium gas. Pitch is the vibration of the vocal folds in the larynx. These vibrations are not effected by helium.
  
  

Facts About Helium

• Helium is the second most abundant gas in the universe. Normal air contains approximately 78 percent nitrogen in addition to oxygen and some other gases. Nitrogen has seven times the mass of helium. Helium allows sound waves to travel through it faster, causing a change in the rate of vibration in the throat when speaking. This change in vibration causes the change in timbre. Faster vibrations cause a higher timbre.
  
  

Other Gases

• Helium raises the timbre of the voice. Heavier gases cause the vibrations to slow. Slower vibrations create a lower timbre. Xenon is an example of a heavier gas that can be inhaled to demonstrate this change in timbre.
  
  

Cautions

• Lightheadedness is a symptom of oxygen deprivation. Inhaling any gas replaces oxygen in your lungs and can lead to asphyxiation. Never inhale from a pressurized tank. This can cause lung damage or force the gas into your bloodstream, which may lead to a stroke or death.