Sound for Interaction class 10

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Sampling theory

Sample process.GIF

sampling process

Quantization Error

Difference between the actual analog value and the quantized digital value due to rounding (or truncating)

aka signal to error ratio



Error due to under sampling
Nyquist Sampling Rate  = 2 * highest frequency


Time synchronization error


Bit Depth

over 24 bit used mainly for internal processing and really high end audio equipment 24 bit Professional recording and internal processing 16 bit CD quality audio (not so good for processing) 8 bit Smaller size used for consumer voice stuff and multimedia

Sampling Rates

Some Common Sampling Rates

Sampling Rate Use
2,822,400 Hz SACD
192kHz Professional recording
96kHz Professional recording Modern Sound Cards HDDVD BlueRay SACD etc
48 kHz Professional recording (commonly used for TV/film)
44.1 kHz CD quality Audio
32 kHz miniDV digital video camcorder, DAT (LP mode)
22 kHz lower-quality PCM and MPEG audio
11 kHz Multimedia/ Games
8 kHz telephone, adequate for human speech

File Size per Sampling rate and Bit Depth

Sample Rate Bit WidthFile Size per minute
96 kHz 24-bit Stereo 33.0 MB
44.1 kHz 16-bit Stereo 10.5 MB
44.1 kHz 16-bit Mono 5.3 MB
44.1 kHz 8-bit Stereo 5.3 MB
44.1 kHz 8-bit Mono 2.6 MB
22 kHz 16-bit Stereo 5.3 MB
22 kHz 16-bit Mono 2.6 MB
22 kHz 8-bit Stereo 2.6 MB
22 kHz 8-bit Mono 1.3 MB
11 kHz 16-bit Stereo 2.6 MB
11 kHz 16-bit Mono 1.3 MB
11 kHz 8-bit Stereo 1.3 MB
11 kHz 8-bit Mono 660 KB
  Note : Dropping the Sampling Rate or Bit Depth by half leads to half the file size

Audio File formats

name ext. info
aiff .aif audio interchange file format (mac native) supports markers and regions
sd2 .sd2 sound designer 2 (digidesign native) supports markers and regions
wave .wav wave file (Microsoft) many different formats most support markerz and regions
au-law .au or .aul au-law file (unix native) supports compression
RAM .ram or .ra Real audio File supports compression and streaming
Mpeg3 .mp3 Mpeg layer 3 supports variable compression and streaming (AMP)
AAC .aac Mpeg2 Advanced Audio Coding AC-3 standard NEW not supported yet
MIDI .mid not and audio format
Modular (MOD) .mod kinda an audio format (used mainly for games)
ASF wmv .asf .wmv windows Media and Advanced Streaming Format Microsoft supports variable compression streaming video encryption

CD Formats

  • RedBook Audio standard CD audio format
  • CDROM-XA (eXtended Archetecture) audio and data


Sound for Interaction Music looping and editing