ID Code: H4-68
Purpose: Play and compare various MP3 compressions of a short musical CD exerpt.
Description: "Were diu werlt alle min," a 50-second piece from Carmina Burana by Carl Orff (1895-1982) has been compressed by an MP3 program to several bitrates: 224 kB/s, 56 kB/s, 40 kB/s, 24 kB/s, 18 kB/s, and 8 kB/s. A nice way to do the experiment is to play the samples in order of decreasing bitrate and ask your students to listen for any degradation in sound quality. The words of the piece, translated from medieval German into English, are: If all the world were mine from the sea to the Rhine, I would give it up to have the Queen of England lying in my arms. Some things to look for as the sound deteriorates include: 1. trumpet tone quality in opening fanfare. 2. clarity of the voices. 3. full sound of the timpani. 4. fidelity of the crashing cymbal. If you use the computer, you can play the samples on the Windows Media Player, which has a variety of visualizations of the waves, one of which (called bars) is simply a spectral analysis of the sound. This allows you to see how the sound spectrum is being limited as the bitrate is reduced.
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