Simple description of the techniques used within each file for compression and data storage, including:

• RAW (PCM)
• RIFF (ADPCM) (including WAV)
• MP3 (description of factors involved)

Pulse Code Modulation is a way of storing digital file formats. The files are uncompressed and each sample is stored in a bit stream.

Adaptive Differential Pulse Code Modulation works in a similar way to PCM but only the change in the samples is stored, this lossless compression technique gives for smaller file sizes (and therefore lower bitrates) for the same data when compared to a PCM file.

MP3 – This is a lossy (the data removed can never be recovered)  sound compression technique that reduces file sizes. It does this by

• removing high or low pitched sounds that humans can’t hear
• When two sound occur at the same time the significantly quieter one is removed.
• The emphasis is placed on the frequencies that humans hear the best.