# Acoustics - Chapter 3 Acoustics Acoustic The study of sound...

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Chapter 3: Acoustics Acoustic: The study of sound Speech can be defined as a continuously changing stream of sound sound is a set of movements or disturbances in the air or some other medium most sounds are complex due to: they result in a complex pattern of vibration pattern sounds are made up of many frequencies all generated at once Pure-tone not many (if any) occur in nature best example is a tuning fork (made to vibrate at only 1 frequency) Simple harmonic motion Simple Harmonic motion results in a pure-tone no matter how hard the tuning fork is struck, it will always vibrate at the same frequency Elasticity : restoring force which causes particles in an elastic medium to bounce back toward their place of rest when they're disturbed. Air is an elastic medium Inertia : the tendency of an object at rest to stay at rest and the tendency of something in motion to stay in motion. It takes far less energy to stay at rest when at rest or to stay in motion when in motion All of the air molecules surrounding the tuning fork exhibits the same vibration, forcing the molecules away from their place at rest then elasticity and inertia keep them moving each air molecule striking another air molecule until all are vibrating the same as the tuning fork when the air particles are close together they form areas of compression when the air particles are further apart they form areas of rarefaction Pressure waves : waves of compression and rarefaction that reach your ear. This is how you hear The harder the strike the further the air molecule is displaced from its point of rest and therefore strike the eardrum with more force causing a louder sound The further the air particles are displaced from rest, the louder the sound will appear Dampening : In time friction will slow down the displacement of air molecules and will decrease the intensity Period of sound : the time it takes for one cycle of vibration to occur Velocity : speed in a certain Direction Acceleration : change in velocity Frequency : number of cycles per second (cps) Fig. 3.3 Fig. 3.4 Maximum displacement decreases the longer the vibration occurs loudness will diminish but frequency will remain the same

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Essential Constituents of Sound 1. Something moving in order to generate a sound pressure wave 2. Medium for the waves to travel through 3. Must be responsible for producing a corresponding movement in the receiver (something must be there to receive the vibration and replicate the pressure wave)
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## This note was uploaded on 01/17/2012 for the course SPTH 3311 taught by Professor Logan during the Fall '11 term at University of Central Arkansas.

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Acoustics - Chapter 3 Acoustics Acoustic The study of sound...

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