The voice of a person, who has inhaled helium, has a remarkably high pitch. Explain on the basis of resonant vibration of vocal cord filled with air and with helium.
The resonant frequency of the vocal cord in the voice box is directly proportional to the speed of the sound. The voice box of a person inhaling helium has helium-filled in it. The speed of sound in helium is about three times more than in the air. Hence the resonant frequency is higher in this case. Therefore, his voice will be of high pitch.