Basic Acoustics

Sound – your ears’ response to vibrations in the air. Sound waves are three dimensional traveling in all directions. Think of dropping a pebble into a pool of water. Sound can be directional Air molecules themselves don’t move very far, instead transferring energy to nearby molecules

Sound Wave One Cycle Zero Crossings

Wave Properties Frequency – Cycles per second – Hertz (Hz) – Perceived as Pitch Amplitude – Amount of air being displaced – Measured in decibels (dB) – Perceived as Volume

Timbre Timbre is defined by the harmonic content Overtones are present to some degree in all sound except sine waves Lowest frequency is the fundamental Each tone is called a harmonic or partial Doubling a partial number results in a pitch one octave higher Harmonic Series

Fourier Theorem Any periodic complex wave can be broken down into sine wave components Basis of additive synthesis – Hammond Organ Sum of two sine wave

Basic Waveforms Sine Wave – fundamental onlyTriangle Wave – odd partials amplitude = 1/n 2 Sawtooth Wave – all partials Amplitude = 1/n Square Wave – odd partials Amplitude = 1/n