From AI as is:
A sound wave represents changes in pressure in a medium—usually air—as the sound travels.
In air, molecules vibrate back and forth, creating alternating regions of:
- Compression — higher pressure
- Rarefaction — lower pressure
So when you see a sound-wave graph, the vertical axis usually represents pressure variation or signal amplitude, while the horizontal axis represents time or distance.
A simple sinusoidal sound wave:
Amplitude / Pressure
↑
| /‾\ /‾\
| / \ / \
------|----/-----\--/-----\----→ Time
| / \/ \
| /Important points:
- Amplitude → relates to sound intensity/loudness
- Frequency → relates to pitch
- Wavelength → distance between repeating points such as two compressions
- Period → time for one complete cycle
One important clarification: the wavy line does not mean air molecules themselves travel in a sine-wave path. The molecules mainly move back and forth around their normal positions while the pressure disturbance travels forward.
