Computers can’t read continuous signals. Instead they need digits, blocks of information which they can process.
Sound wave vibrations in the air are continuous streams of information. Therefore, for computers to be able to understand sound wave information they need to convert this continuous signal into blocks of information which they can process.
Analogue to Digital converters (ADC) transform continuous sound wave information into digital chunks.
They do this by taking a snapshots of the sound wave at a specified rate. The more chunks that the computers store every second, gives a more accurate picture of the sound wave.
(USE VISUAL EXAMPLE OF FRAME RATE TO DEMONSTRATE THIS CONCEPT).
Manipulating the Information
The digital information held about sounds can be processed and transformed in ways that analogue signals cannot. This has allowed composers to do much more complex sound transformations and to work with sounds in an almost unlimited fashion.
One key advantage in having sound information stored digitally is that it can be copied, transferred, duplicated and rewritten without any loss in quality.
This process of taking snapshots at a specific speed is called the Sampling Rate. The higher the rate of sampling, the smoother and more accurate the digital imprint of the original signal. Sample Rate is the term used to describe the number of snapshots taken every second and is measured in Hz (like frequency, number of cycles per second).
The higher the sample rate, the more information is collected about the original sound, and therefore the more accurately the original sound can be reproduced. However more information = more space taken up.
The Sample Rate of CD quality stereo audio is 44100Hz samples per second (44.1kHz), on DVD’s alongside picture the stereo audio sample rate is 48000Hz (48kHz), and on purely audio DVD’s the stereo audio sample rate is 96000kHz (96kHz).
We need to strike a balance between file size and detail, and because the human ear can only hear up to 20kHz the people who designed CD’s decided that we didn’t need to have a sample rate any higher than 44.1kHz (20.5kHz per channel).
Sample Rate allows us to capture detail in terms of frequencies.
Bit Depth allows us to capture detail in terms of amplitude.