What is sound?
Sound is made when something vibrates. These vibrations travel through air, water, or other materials as waves of higher and lower pressure.
How sound moves
Sound travels as a chain reaction. One particle moves and pushes the next. This creates a wave that reaches your ear.
Compression and rarefaction
A sound wave moves by repeating two phases:
- Compression: air particles are pushed closer together.
- Rarefaction: air particles spread apart again.
These two phases matter because they are what carry the sound through the air. When something vibrates, it pushes the air (compression) and then pulls back (rarefaction). This push and pull travels outward in a wave. Your ear detects these tiny pressure changes and your brain turns them into sound. Without this cycle of compression and rarefaction, vibrations would not travel and you would not hear anything.
Speed of sound
Sound travels at about 344 metres per second in air at normal temperature. All sounds move at the same speed in the same material.
Frequency
Frequency is how many wave cycles happen each second. It is measured in Hertz (Hz). Higher frequencies sound higher in pitch. Lower frequencies sound lower.
Wavelength
Wavelength is the distance a wave travels during one cycle. Low frequencies have long wavelengths. High frequencies have short wavelengths.
Amplitude
Amplitude shows how strong the pressure changes are in a sound wave. Higher amplitude means a louder sound. Loudness is measured in decibels (dB).