Home / Topics / Waves & Sound
Speed of sound
Beginner
About 343 m/s in air at 20 °C.
v = 331 + 0.6TIn air v ≈ 331 + 0.6T (°C) m/s. It rises with temperature and does not depend on pressure at constant temperature.
At 20 °C: 343 m/s.
Higher humidity raises it slightly.
In more detail
The speed of sound in air is about 343 m/s at 20 degrees Celsius. It increases with temperature and is independent of the pressure at a fixed temperature.
Real-world uses
- Lightning distance is estimated by counting seconds between flash and thunder.
- Sonar and echo location depend on the speed of sound in water.
- A sound check uses the speed of sound to estimate the distance of a thunderclap by counting the seconds after the lightning.
Open the interactive lesson, with simulation and quiz →
Frequently asked questions
Why does temperature change the speed?
Warmer air has more kinetic energy, so pressure disturbances travel faster.
Does humidity matter?
Slightly. Moist air is less dense, so sound travels a little faster.
Why does sound travel faster on a warm day?
Warmer air has faster-moving molecules, so the sound wave passes from particle to particle more quickly.
Related topics in Waves & Sound
Wave number · Wave speed on a string · Wave speed in a medium · Speed of sound in gases · Reflection of waves · Phase change on reflection