Making Sound Digital

The audio CD that contains digital sound has become the fidelity standard of the music industry. But before digital sound, there were phonographs. Phonographs produce audio from LP albums recorded in analog format. The audio waveforms are physically represented as grooves in a record. Playing the record is accomplished by spinning the album with a crystalline phonograph needle resting in the grooves.

The flexing of the needle produces a small electric current which is converted into an audio waveform and amplified until it comes out your speakers as music. This process works wonderfully when you have perfect needles and absolutely clean grooves. Anything less than perfection, however, causes the inevitable distortion all phonograph users hear as pops, clicks, and skips. This distortion of sound is the reason that digital audio has become so popular.

Translating an analog waveform into a digital form works by taking tiny (discrete) samples of the waveform at fixed intervals as the sound is captured. This process establishes the frequency of the waveform. At the same time, the values for the waveform's amplitudes are also captured defining the amount of information stored per sample.

Each sample is mapped to an integer value, which is then stored. These integer values can then be used to recreate the original waveform. The result: quality sound practically indistinguishable from the original.

Compact disc audio is the highest quality format, but produces the largest
files. Other formats store sound files more economically, but with some trade-off in quality.