Compact Discs
Compact Discs (CDs) were first produced in the 1980s as a new and improved medium for listening to music. At the time, they were cutting edge due to being a digital way to record sound. This meant CDs offered superior sound quality to cassette tapes, could store significantly more data and were easier to navigate - enabling movement from the beginning of one track to the beginning of another, rather than having to fast forward or rewind and guess where the tracks started and finished.
Over time, CDs have progressed from being solely for music, to being a format for all kinds of data storage, such as text, images, photos and videos.
CD as a medium for accessing information
CDs are a physical medium by which to deliver information, but the information can be stored on them in many different ways. The format in which information is stored on a CD affects functionality, including the quantity of information which can be stored, sound quality, how easy it is to navigate and so on.
There are a range of electronic audio formats which can be stored on CD, the most popular of which are:
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CDDA - the standard format for most audio CDs
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MP3 - a compressed audio format enabling greater storage capacity, but lower quality sound
CDDA
When CDs were first launched, CDDA (Compact Disc Digital Audio) was the most common format used for storing audio information on CDs.
As digital technology progressed, and CDs replaced cassettes to become the preferred medium to deliver audio and data, the MP3 format was developed to increase the amount of information that could be delivered on a CD.
MP3
MP3 is a digital audio encoding format that compresses the original audio recording, enabling more data to be put on a CD than if the data was in CDDA format.
DAISY (Digital Accessible Information SYstem) is a format developed by the DAISY Consortium, an international group, promoting digital technology for talking books. The DAISY format uses MP3 encoding to compress the audio recording - enabling around 20 hours of audio to be presented on one CD.
CD players
CD players that only accept and play the CDDA format are becoming obsolete - being replaced with digital audio players that will accept a range of formats including MP3. This development is good news for the consumer - giving them access to more information and formats on a single CD and enables the audio producer to supply information more cost effectively.
Blind and Partially Sighted people and CDs
The shift to digital audio also has benefits for users of audio formats. In particular, for those who read audio books, the increased capacity of CDs over tapes means a long book can be delivered on just one CD!
As discussed, the format in which information is stored on CD affects usability, therefore some people may have had bad experiences with CDs - for example, difficulty trying to find the place they left off. However, developments such as DAISY offer many features designed to improve the experience of talking books for blind and partially sighted people.
It must be recognised that some blind or partially sighted people may not be confident in using new technology, therefore support and training may be required in order for them to feel comfortable with the move from analogue to digital audio.