Lecture 1 Sound - Movement

The velocity of sound changes depending on what the sound is moving through, The standard for sound to move through air is 333m/s which is roughly 700mph but sound moves much faster through water at 1500m/s and even faster through steel 5000m/s. So sound traveling through air down the length of a football pitch (120m) would take : 120/333s - 0.36s. It would take around a third of a second for the sound to make it down the whole pitch. If the pitch was full of water it would take even less time: 120/1500s - 0.08s.

The frequency of a wave is the number of complete cycles per second and this is measures in Hertz (Hz).

The velocity of a wave length can be figured out by multiplying the wavelength by the frequency.

V= λ x f  m/s  , this equation can shuffled round to work out different parts. It can be used to find the wavelength by changing it round to  λ= v/f m . 

So a 1kHz tone in air has a wavelength, 
l = v/f m 
= 333/1000 m 
= 0.333 m 

 Harmonics


Sound is made up of vibrations, there is the main vibration which is the fundamental tone and other vibrations are the harmonic tones. 
" A harmonic is an integer multiple of the fundamental frequency e.g. 2 x fundamental, 3 x fundamental, etc. 
So a sound consisting of components at frequencies of 1000 Hz and 3000 Hz would contain a 3rd harmonic of the 1 kHz fundamental.  "