The Sound System

Modern computers have an expansion card and external stereo speakers that can play digitized speech, and multiple-voice music. There is also a little speaker in most computers which is sort of an appendix. Originally, computers had this single little speaker only, and the computers were capable of generating only simple tones through it. You could hear boops and beeps - that was it. Software engineers took this as far as it could go. Eventually, they could coax melodies and speech out of the little speaker, but it was unclear and staticy. Whenever a sound was playing through the speaker, the computer paused, it could do nothing else, until the sound was completed. Then, auxiliary, stereo sound systems were developed, and the original speaker has been all but forgotten.

There is a lot of data in sound. Sound files would be huge if they were not compressed. Fortunately, they are much smaller due to two types of compression technology. The first is based on straight digitized recording. Sounds are recorded verbatim, for each second of sound, a stock number of bytes are used to track the vibrations. Then, the bytes are analyzed for recurring patterns, and each pattern found is assigned a number. These numbers are recorded in the sound file instead of the actual patterns they represent, saving lots of space. Similar compression is usually used for picture files, and files which are compressed for modem-based transmission.

The other technique is used by .MID (Midi) files. In this technique, rules and codes are assigned to sound concepts - the voices of instruments, frequencies, and durations. Then music is recorded not by digitizing the actual vibrations, but by packing the codes for which instruments, which notes and how long to play them into a file. Any computer capable of playing Midi sound files then has the knowledge to read the codes from the file, and recreate the sound using the same rules.

Digitized sound is best when you need an accurate representation of actual sound, such as speech, or special effects. However, Midi sound files are generally much smaller than digitized files.

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