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Sound for Sound Engineers	Level:	Basic Advanced Professional
Original site content © 2001, 2002 V.Karazija/Audio Training Consultants Pty Ltd. All rights reserved.	Code:	DEMO 3

	This module was last updated 25 April 2002
Chapter 1 : The Nature of Sound : Part 3 of 5	Go to Chapter:

Contents

Part 1

Part 2

Part 3

Part 4

Part 5

To Chapter 2

Part 3 - How Sound Travels
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What the air particles are doing ...

The air particles next to a sound source are forced into vibration.

Just like the vibrating drum head on a bongo, or the cone of a speaker, each air particle just moves backwards and forwards around its normal 'resting' position.

It's almost as if each air particle was attached to an imaginary spring, oscillating in the same direction that the sound wave is travelling.

As the particle moves towards the next one, it causes it to move in turn a short time later. Because of the time delay in transferring energy from one particle to another, the particles bunch up forming high pressure (compression) zones. Between the compressions, they spread out to form low pressure (rarefaction) zones.

A short, sharp sound - like a click from a speaker - will cause the air particles nearest the cone to oscillate once and then come to rest. The mechanical energy from the cone is transferred from particle to particle until it reaches the listener.

What the sound wave itself is doing ...

The compression and rarefaction zones move through the air from the source to you. This happens at the speed of sound - about 1100 feet/second or 340 metres/second.

We call this movement of the pressure zones the sound wave. The particles which carry the wave don't move very far at all. However the sound wave itself can travel long distances and transfer the energy of the source to the final destination.

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Sound for Sound Engineers

Chapter 1 : The Nature of Sound : Part 3 of 5

What the air particles are doing ...

What the sound wave itself is doing ...