High and low sounds
Fast vibrations make high sounds.
High and low
Pitch is how high or low a sound is. A whistle and a bird’s song have a high pitch. A big drum and a cow’s moo have a low pitch.
Elephants can make very low rumbles that travel for kilometres, and bats make squeaks too high for people to hear.
Fast and slow vibrations
Fast vibrations make high-pitched sounds. Slow vibrations make low-pitched sounds. The number of vibrations each second is called the frequency.
Frequency is measured in hertz (Hz). People can hear from about 20 Hz to about 20,000 Hz; children can usually hear higher sounds than adults.
Try it with a ruler
Hold a ruler over the edge of a desk and twang it. With a long part hanging over, it vibrates slowly – a low sound. Make it shorter and it vibrates faster – a higher sound.
This is the same idea as a sitar or ektara: pressing a string shorter makes it vibrate faster and play a higher note.
Voices
Your voice comes from vocal cords in your throat that vibrate. Children have shorter vocal cords than adults, so their voices are usually higher.
Singers can change the pitch of their voice by tightening or relaxing their vocal cords.
What I learnt
- I know that pitch is how high or low a sound is.
- I know that fast vibrations make high sounds and slow vibrations make low sounds.