The science of frequency and amplitude
For music, frequency determines pitch. The more quickly an object oscillates, the shorter the cycle between compression and rarefaction and the higher the pitch becomes. If two oscillations occur at different frequencies, both may begin at the same zero point, but the higher frequency would complete more cycles than the lower in the same amount of time. Alongside pitch and timbre, a final character of sound is amplitude. Changes in amplitude are a result of the number of air molecules an oscillating object displaces. Amplitude is measured by the degree of motion of air molecules that correspond to the extent of rarefaction and compression that accompanies the wave. Decibels are an appropriate measurement for audio because they accurately represent the non-linearity curve of human hearing and permit for a sizeable audible range. Weighting filters are a number of different filters that reduce or enhance specific frequencies along the sonic spectrum.