Case Study mp3

Case Study mp3 Soundtest / Home

The Hearing Test

The 51 minutes of signals were burned on a single CD in order to avoid having to play dj during the hearing test. The drawback was that during the hearing test, everyone knew exactly which version they were listening to. The order was: original CD, analog recording and then, depending on the piece, either the very close or clearly worse mp3 recording. The differences between the single and double converted files could only be guessed. The results in detail:

• 2-Tone Signal All variations about the same. The 200hz differential signal could be heard clearly over the headphones!
• Sinus Bursts Noise veils for the mp3, even for low levels. The overshooting is probably less of a problem.
• Mariah Carey The mp3 pulse less sharp, voice doesn’t sound clean. Analog recording better than mp3.
• Tom Jones mp3 less impulsive, otherwise relatively good.
• Piano Music mp3 hisses, analog recording clearly better
• Symphonies mp3 hisses, but good over broad sections, especiallyat 256kBits/s. The analog recording is clearly better and only has minimally more noise than CD.
• Chamber Music Hissing in mp3
• Speech Minimal hiss in mp3

It is interesting to note that the slight overdrive (a few percent) during the analog recording of Tchaikovsky’s Sixth Symphony were hardly audible. The ruling after this round is clear; mp3 is okay, but not for high demands, although the negative effects are small over broad sections. The analog recording is surprisingly good in spite of a $50 sound card. There was no desire for additional tests, the results were clear. There was no shortage of ideas, though (20bit Chopin with Kissin, techno or opera). It should be mentioned that some old-style ISA sound card and also some modern cheap on-board cards are much worse.

After this training period a blind test have been performed. The error quote was supprisingly small at 10%. Most difficulties occurs at the Tom Jones hit. The analog recording was pretty good but the noise level was a little bit increased. Mp3 reduces the dynamic and sometimes creates hiss.

Detective Needed
Conclusion

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