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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 2

	This module was last updated 25 April 2002
Chapter 1 : The Nature of Sound : Part 2 of 5	Go to Chapter:

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Part 1

Part 2

Part 3

Part 4

Part 5

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Part 2 - How Sound is Made
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How sound is made

Sounds can be created in many different ways, which can include hitting a drum, plucking a string, blowing a horn, singing or moving a speaker cone. But no matter what the sound, it always starts as a mechanical vibration. Sound sources vibrate - it's as simple as that.

The energy of the vibrating parts is transferred to a medium, usually air, and travels as a sound wave through that medium.

For example, when the head of a bongo drum is struck, it vibrates up and down. As it moves down, the air particles beneath it are pushed closer together - forming a zone of compression, or higher pressure.

Then the head tension makes it move in the opposite direction, so the air particles beneath move further apart, forming a zone of rarefaction (say rare-ra-faction) or lower pressure.

This oscillating motion causes alternating compressions and rarefactions which spread out from the source in all directions through the air.

The diagram shows these pressure zones at a frozen instant in time - in reality they are moving rapidly away from the sound source.

The thing is, while the high and low pressure zones move steadily away from the sound source, the medium itself - the air particles through which the sound moves - behaves quite differently.

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Sound for Sound Engineers

Chapter 1 : The Nature of Sound : Part 2 of 5

How sound is made