- Sound waves are caused by vibrations such as that from a tuning fork, a loudspeaker cone, or the human voice.
- These vibrations need air to travel through. They cannot travel through a vacuum.
- The air itself doesn't travel.
- The sound causes compression and decompression of the air as it moves through it.
- There is a regular spacing between one pressure peak and the next.
- This distance is called the WAVELENGTH.
- Sound travels at about 330 metres a second.
- A pure sound tone consists of a single frequency of vibration.
- The range of human hearing is about 20 Hertz to 20 KiloHertz.
- Most sounds are a mixture of frequencies. See the page on HARMONICS.
- Microphones convert sound pressure waves into electrical signals.
- Loudspeakers convert electrical signals into sound waves.
- Loudspeakers and microphones are TRANSDUCERS.
- Frequency, wavelength and the speed of sound are interrelated.
Wavelength x frequency = the speed of sound in metres per second.