### What is sound?

Sound is generally defined as a mechanical vibration in a transmission medium (e.g. air). These vibrations propagate in the shape of sound waves. In air, sound waves are pressure and density fluctuations. If those fluctuations happen periodically between 16 and 18.000 times per second, we perceive these sound waves as sound. Frequency = number of oscillations per second, measured in Hz (Hertz)

Amplitude = max. extent of the wave’s displacement from its rest position / intensity of the density fluctuation

Period = duration of one oscillation ### What‘s the speed of sound?

Sound requires a medium (solid, liquid or gas) with a certain mass and elasticity. It is these factors as well as the temperature that influence the speed at which sound propagates.

Air at 20°C  = 343m/s

Helium at 20°C = 1005m/s

Sea water at 20°C = 1560m/s

Diamond at 20°C = 17500m/s

Speeds in comparison:

Fastest human  = 10m/s=36km/h

Formula 1 Car = 100m/s=360km/h

Sound in air = 343m/s=1234,8km/h

Light = 300,000,000 m/s

### Did you know that…

... the speed of sound in air at 20 degrees is 343 meters per second and in sea water at 1560 meters per second – that‘s more than four times the speed!