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Introduction to Digital Audio

Objectives
Explain the difference between analog and digital signals
Identify audio sampling standards
Describe audio sampling variables
Determine how variables affect file size and quality

Analog vs. Digital Signals
Analog –
A continuously recorded sine wave signal usually recorded on a magnetic medium

Analog vs. Digital Signals
Digital –
A signal that samples specified portions of a signal resulting in discrete digital information (i.e. bits of data)
“ Sampled” discrete data

Audio Sampling Variables
Three main criteria:
How many samples? OR “sampling rate”
How much data per sample? OR “bit depth”
How many channels sampled?

How Many Samples? Audio “Sampling Rates”
Digital Video
CD Quality
Stereo
FM Radio
AM Radio
Telephone

Digital Video
48,000 per sec
32,000 per sec

CD Quality
44,100 per sec
Left & Right
Channels Combined

Other Sample Rates
Typical Sample Rates: Sample Rate Less 8000 Quality Telephone 11000 AM Radio 16000 FM Radio 22050 per Stereo

How Much Data per Sample?
Common Sampling
“ Bit Depth”
8 bits of data
per sample
16 bits of data
per sample

How Many Channels Sampled?
Number of Channels
Stereo (2 channels)
Mono (1 channel)
Multiple tracks

Audio Sampling Variables File Size Digital Audio Quality

Audio Sampling Variables
Balance Sample Rate Bit Depth Number of Channels Record Settings Sound Quality File Size

Audio Record Rate
More Audio Samples Larger Audio Files

Audio File Size
File size is determined by a combination of: Bit Depth Sample Rate No of Channels

Audio File Size
File size is determined by a combination of: Length in Minutes Bit Depth Sample Rate No of Channels

Audio File Size
Variables of concern: 8 bit or 16 bit Various Sample Rates Stereo or Mono Length in Minutes

Digaudio

by Institute of enginering and technology on Nov 17, 2009

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