Digital audio can be recorded on storage device as a stream of numbers, representing the changes in air pressure. Recording is often carried out on a computer, using a program like Audition or Audacity, but can also be done using a Digital Audio Recorder which stores the recorded files on an SD Card.
Ordinary analogue audio is made up of a continuous wave which varies in frequency (pitch) and amplitude (volume). This needs to be converted into a stream of numbers before it can be recorded in digital form. This conversion is done by an Analogue to Digital Converter (ADC). The reverse process takes place before playback – the digital audio information is converted back to analogue format by a Digital to Analogue Converter (DAC).
A number of factors can influence the quality of a digital recording. The most important ones are the sampling rate (how often the analogue sound is converted to digital) and the bit depth (the range of numbers used to represent the analogue sound). A high sampling rate and a high bit depth will increase the quality of the recording, but will also increase the size.
Digital audio files can be copied from one storage device, such as a hard disk and stored on another, such as a recordable CD or DVD or an SD Card. It can alo be copied to other devices, such as a portable Media Player. The process of transferring audio to a CD or DVD is known as burning and requires the use of a CD or DVD writer and special software. One commonly used package is Nero Burning ROM.The software can be used to create standard audio CDs, but it can alo be used to create data CDs, containing programs and/or data files, and mixed-mode CDs, containing both audio and data files. Mixed-mode CDs can only be played on a computer – they cannot be played on normal audio CD players.
Most digital audio files, including those bought on CD or downloaded from the Internet, are copyright and should not be copied without the permission of the copyright owner. Some digital audio files cannot be copied, or can be copied only a limited number of times, due to the presence of Copy Protection or Digital Rights Management (DRM) software.
Software is also available for converting between different digital audio formats. For example, you may wish to store digital audio files on your computer in FLAC format, in order to maintain the highest possible quality, but convert them to MP3 format before copying them to your Digital Media Player in order to minimise size.Again, copyright restrictions must be kept in mind.
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