Unit 3 Properties of waves
Sound wave characteristics
- The speed of sound varies from material to material. A sound wave compresses (pushes together) and rarefies (spreads apart) the particles of the material, and how easily this happens affects the speed of the wave.
- Sound travels fastest in solids because the molecules in a solid are very close together.
- Sound travels second fastest in liquids because the molecules in a liquid are only slightly further apart.
- Sound travels slowest in gases because the molecules in a gas are far apart.
- Remember: Sound cannot travel through a vacuum because there are no particles.
- Some examples of the speed of sound in different media are given below.
- In dry air at 0°C the speed is 330m/s.
- In dry air at 20°C the speed is 340m/s.
- In water the speed is 1500m/s.
- In gold the speed is 3200m/s.
- In steel the speed is 5800m/s.
- Frequency, pitch, wavelength and amplitude are terms associated with sound waves.
- Frequency is the number of wavelengths produced per second and its unit is the hertz (Hz).
- Pitch is how high or low a sound is and is dependent on frequency.
- Wavelength is the distance from any point on one wave to the same point on the adjacent wave. Its unit is the metre (m).