BUY THE YEAR 9 PHYSICS WORKBOOK

Speed of Sound

  • The velocity (speed) of a wave is also mathematically related to distance and time, as shown in the following formulas.
  • In terms of speed:

wave formula speed distance time

 

  • In terms of distance:

wave formula distance speed time

 

  • In terms of time:

wave formula time speed distance

 

  • We saw in the lesson ‘Waves’ that the speed of a wave depends on the medium through which it travels.
  • We saw that mechanical waves, such as sound waves, travel fastest in solids and slowest in gases.
  • This is because the more closely packed particles in a substance are, the more efficiently they can transfer the wave.
  • Examples
  • The speed of sound in air is approximately 340 m/s.
  • The speed of sound in water is approximately 1500 m/s.
  • The speed of sound in concrete is approximately 3000 m/s.
  • The speed of sound is also affected by temperature. Particles are moving faster in hotter objects than in cooler objects, therefore sound waves can travel more efficiently through them.
  • Examples
  • The speed of sound in air at 0 °C is approximately 331 m/s.
  • The speed of sound in air at 25 °C is approximately 346 m/s.
  • The speed of sound in air at 45 °C is approximately 358 m/s.
  • The speed of sound in air is also affected by the composition and density of the air, including the amount of water vapour.
  • For example, sound travels slightly faster in humid air than in dry air.

 
temperature and speed of sound in air

The speed of sound varies with temperature.

 

(Header image: Thaut Images, Adobe Stock)