Sound travels in waves. These waves vibrate the medium that they travel in. When these vibrations enter your ear, they vibrate small
hairs in your ear and that sends a message to your brain and tells you what you're hearing.
Sound travels at 762mph through air. The speed at which sound travels at varies between different mediums.
The higher the pitch of sound the less distance it will travel, likewise a lower pitch sound will travel much further. This happens because if you look at a diagram you can see that lower pitch waves are more spread out, covering a greater distance.
Sound is heard in many pitches and can vary in volume a lot. But why can the pitch and volume vary so much?
Well there are two units measurement used to measure sound. Decibels measure the volume and hertz measures the pitch.
Decibels measure the volume of the sound. Sound travels in waves just like in the sea. The stronger the waves the higher the decibels.
You would think that 140 dB (that's short for decibels) would be twice as loud as 70 dB when in fact 80 dB is twice as loud as 70dB.
If you take a speaker and take the pitch right down so that you could see the speaker cone vibrating, the hertz is the amount of times that speaker vibrates every second.