Sound Boards
Basic concepts
- sound = vibrations on air or other substances
- sound properties: pitch and intensity
- pitch - rate the vibrations are produced in Hz (humans can hear 16Hz-20KHz)
- intensity (amplitude) - strenght of the vibrations in db
- sound formats: wav, aiff, au, etc
Functions
- convert from analog to digital (record)
- convert from digital to analog (play)
Measures
- frequency response (30Hz to 20KHz)
- harmonic distortion (accuracy of sound reproduction)
- sampling (snapshots of the analog sounds) - 11KHz, 22 KHz, 44KHz
- resolution (bits to digitize sounds) - 8, 16 and 32
- channels (mono or stereo)
file size = minutes x sampling x resolution x channels
for example 1 minute at 22 KHz 16-bit mono = 5.3 MB
CODEC (Compression/Decompression)
- TrueSpeech (10:1)
- ADPCM ( from 2:1 to 4:1)
- MPEG (12:1)
- DSP (digital signal processors)
- streaming audio (Web)
Types
- FM-synthesis (overlaped, modulated sine waves .wav)
- wave-table (ROM stored sounds)
- MIDI-interface (description of a sound to be played in MIDI synthesizer)
Other references