Our voices are incredibly distinctive, created by vibrations in our voice boxes at unique frequencies. These frequencies start off consistent, but this changes, so when helium is introduced, being lighter than air it can affect these frequencies. Helium and air are both gases with very similar compressibility so the much lower density of helium causes sound waves to propagate about 2.7 times faster. Your voice doesn't actually change pitch with a lungful of helium: your vocal chords still vibrate at the same frequency. When you inhale helium, you're changing the type of gas molecules in your vocal tract and increasing the speed of the sound of your voice. Discover the real science behind the Donald Duck effect. Learn how gas density affects the speed of sound and why helium doesn't actually change your pitch. The distinctive high-pitched voice produced after inhaling helium is a widely recognized phenomenon. This temporary vocal transformation, while amusing, stems from fundamental principles of physics and acoustics. Sound travels faster in helium so the vibrations will get from your vocal chords to your mouth quicker so your throat will resonate at a higher frequency and hence a higher pitch. Helium changes your voice because sound travels much faster through helium than through regular air. This higher speed raises the resonant frequency of the vocal tract in your mouth and throat, making the sound waves you produce have a higher pitch, resulting in that iconic squeaky, cartoonish voice. Ever wondered why helium turns your voice into a squeaky chipmunk? Dr Matt Agnew breaks down the real science. and it's weirder than you think. Inhaling helium makes the higher-pitched tones resonate more in the vocal tract, amplifying them so they are louder in the mix. At the same time, it makes the lower tones resonate less in the vocal tract. The two effects combine to create a Chipmunk-like, flat sound. Since helium is less dense than air, the sound waves traveling through it move faster, leading to an increase in frequency. As a result, the perceived pitch of your voice becomes higher and squeakier, which is often humorous and amusing, especially to those listening.