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 sonic waves as sound.

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Frequency = number of oscillations per second, measured in Hertz (Hz)

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

Period = duration of one oscillation 

In physics, the wavelength – λ – is the spatial period of a periodic wave — the distance over which the wave’s shape repeats.

\lambda ={\frac {v}{f}}\,\,,

v is called the phase speed (magnitude of the phase velocity) of the wave and f is the wave’s frequency.

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 (343, 2 m/s = 1235,52 km/h) 
  • Helium at 20°C (1005 m/s = 3618 km/h))
  • Sea water at 20°C (1560 m/s = 5616 km/h)
  • Diamond bei 20°C (17500 m/s = 63 000 km/h)

Speeds in comparison:

  • Fastest human (10 m/s = 36 km/h)
  • Formula 1 Car (100 m/s = 360 km/h)
  • Sound in air (343,2 m/s = 1235,52 km/h)
  • Light (299.792.458 m/s = 1.079.252.848,8 km/h)

Did you know that …

the speed of sound in air at 20 degrees celsius is 343 meters per second and in sea water it is 1560 meters per second – this adds up to more than four times the disparity in speed!