Sound Waves
- Sound waves are longitudinal waves and, as such, require a medium in which to propagate
- Sound waves are generated by oscillating sources, which produce a change in density of the surrounding medium
- The sound wave then travels with a series of compressions and rarefactions
A sound wave travelling through air
- Sound waves form a continuous spectrum based on their frequency
The spectrum of sound waves
- Humans can only hear sounds with frequencies in the range 20 Hz - 20 kHz, known as the audible range
- Sounds with frequencies below and above this range cannot be detected by the human ear
Pitch & Volume
- The frequency of a sound wave is related to its pitch
- Sounds with a high pitch have a high frequency (or short wavelength)
- Sounds with a low pitch have a low frequency (or long wavelength)
- The amplitude of a sound wave is related to its volume
- Sounds with a large amplitude have a high volume
- Sounds with a small amplitude have a low volume
Pitch and amplitude of sound
Speed of Sound
- Sound waves travel at a speed of about 340 m s–1 in air at room temperature
- The higher the air temperature, the greater the speed of sound
- The is because the average kinetic energy of the particles is higher
- Sound travels the fastest through solids, since solid particles are closely packed and can pass the oscillations onto their neighbours much faster
- Sound travels the slowest in gases, since gas particles are spread out and less efficient in transferring the oscillations to their neighbours
