- A brief history of the Internet
- A brief history of computer sound
- The soundcard
- Sound file formats
- Traditional music delivery formats
While analogue sound is represented as a time-continuous format (i.e. a waveform), digital audio is the name given to sound or audio data that has been converted into a time-discrete numerical format, which is stored as a series of zeroes and ones known as binary code . Binary code is based on the use of transistors in the original computers that were developed. The binary digits, 1 and 0, each represent a single switch which is either on (1) or off (0), and which can be rapidly controlled by electronic control signals. A single binary digit is known as a bit and is the smallest unit of computer data. An interconnected network of transistors stores and processes computerised information as a series of binary digits which make up a single alpha-numeric character (e.g. a-z, A-Z, 0-9 etc) or a computer command (print, load, copy etc).
Analogue sound, on the other hand, is stored and/or carried by one of four alternate means -
- electrically - as variations of current flowing through a length of wire
- magnetically - as patterns of magnetisation of particles on a length of audio tape
- optically - as a pattern of light and dark on a film soundtrack
- physically - as variations in depth of the groove on a vinyl record.[3]
Digital audio is stored digitally as binary information that can then be manipulated just like any other computer data at high speed by a computer, a process that is known as digital signal processing (DSP). The advantages of digital signal processing are numerous - errors in sound can be corrected, even after recording, using powerful error-correction software. Unlike analogue sound, the sound quality of digital audio is independent of the medium on which it is stored or transmitted, and is stored non-linearly, which means that it can be transmitted discontinually if required, as long as the data is re-assembled in the correct sequence at the user end.
Of utmost importance to the music industry, a digital signal does not degrade through copying, provided that the signal is copied digitally - i.e. the data is copied rather than the analogue output of the digital system.
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