How mp3 compression works - Demo , p213
These are the demonstrations that go along with the talk How MP3 Compression Works: More music, fewer bits by Mark A. Yoder.

There are five demonstrations here.


Quantizing a sinusoid

One of the ways to reduce the size of an audio file is the reduce the number of bits used by each sample. This first demo lets you see and hear the effect of quantizing a sinusoid to various number of bits. The black is a plot of the original sinusoid. The red is it quantized. Initially it's quantized to 8 levels. The blue plot below is the error signal. The error is found by subtracting the original signal from the quantized signal.

Try this:

  1. Click the Play Sound button to hear the original signal followed by the quantized signal followed by the error signal.
  2. Try changing the number of quantization levels. At what point is the quantization noise no longer audible?
  3. When you are finished experimenting with this demo, scroll down to the next.

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Oppenheim and Schafer, Discrete-Time Signal Processing ISBN 0-13-198842-5.
Prentice Hall, Upper Saddle River, NJ 07458. © 2010 Pearson Education, Inc.