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Post  admin on Tue 29 Jun 2010, 7:32 am

Audio data in the form of waveform, as shown in Audacity.

Audio data can be either in the form of sampled audio or MIDI. A waveform file is a sound that has been digitised by making many measurements of a recording's pitch and volume. Each measurement is a sample. Measurements are stored in a file which has information stored about the sound. This is then read by the computer when the file is played, processed by the CPU, and displayed (played through the speakers). This is the computer using samples to approximate the original soundwave. Other sampled audio formats include mp3 and wma. MP3 format for audio has greatly improved quality and decreased both transmission time and storage requirements as opposed to WAV format.

MIDI (Music Instrument Digital Interface) is audio data that contains instructions on how to play music, rather than actual sound measurements. It is very similar to a musical score in binary, and is often used to store information when electronically composing music. It contains data such as pitch, volume, instrument type and duration of each sound in the file. It also has extra details such as how the note starts and ends and the force with which the note is played. Extra files are available that specify the tonal qualities, or "timbre" of an instrument, or simply a recording of the instrument allowing each note to be played by a different instrument. These are not stored within the midi file but on the device such as electronic keyboard or PC. This is similar to a template of sound, so when MIDI values are inserted the "instrument" produces a different sound quality.

Audio when combined in a multimedia presentation is often used to add sound affects or realism to video, add enjoyment through music as well as to reinforce ideas presented in a video or in text. It is rarely used on its own.


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