High Bitrate MP3 Internet Blind Test: Part 2 - RESULTS

Previous - Part I: Procedure

RESULTS:

The final tally for respondents is 151. Here's the updated map of where the responses came from:

As I mentioned in "Part 0", the majority of responses were from North America (64), followed by Europe (47), Asia (33), Australia & New Zealand (4), finally South America (3). It looks like freeonlinesurveys.com may actually not be completely accurate since at least one person indicated they were in Russia which was not highlighted on the map!


First, lets have a look at the demographic that responded to this test in terms of equipment used:

As you can see, the price range (asked to specify in $USD) of the audio gear and system setup varied greatly.  A large proportion of respondents used headphones for the test (23%) which I suspect is reasonable especially given the computer-audio nature. I suspect many of us consider the headphones plugged into the computer/DAC to be superior to whatever speakers may be on the desk. 25% responded to the optional field and actually listed the gear used (thanks!). Depending on the price range, scanning the responses I see a huge range of headphones tested (Beyerdynamic DT990, 880 & DT770 seems popular, a few AudioTechnica M50's & AD700, Sony V6, Creative Aurvana, Senn HD800/650/600/570, Bose QuietComforts, AKG K701, Shure SRH440, Hifiman Re-0, Ultimate Ears Triple-Fi 10, Superlux 668B, Fostex). Likewise a full range of speakers like Martin Logans, PBN Montana, Decware MG944, a couple Magnepans, B&W 802D's, KEF iQ1, Sapphire ST2). It's notable that some folks used a combination of headphones and speakers. Some DIY guys also got involved with their own DAC's - one respondent specified a homemade Sabre DAC. Network streamers were mainly Squeezebox Touch models sent to outboard DAC's, one person listed the Naim NDX. As for DAC's, I see everything from a dCS setup to DragonFly to Mytek to Xonar Essence ST / D2 / One's to Meridians... Looking at the detailed responses, I think I can honestly say that respondents took the test seriously, some describing their test procedure and running foobar2000 ABX tester themselves.

As for which song was felt to be easiest to differentiate between MP3 and lossless:

"Time" was the winner followed by "Church". Interesting given that from Part 1, we can say with some objectivity that it's actually "Keine Zeit" which shows the greatest variance in comparison to the original lossless audio. For most of us, familiarity is important and I think for the demographic, "Time" and "Church" would likely be most accessible (like I said, I had complaints about putting the metal track in the test!). Some respondents would have preferred a classical track as well. I agree this also would have been revealing but it's always a compromise trying to keep the test simple and download size reasonable.

 Perhaps not unexpectedly, most respondents had to work hard or felt it was impossible to tell the difference between the Sets (total 50.7% for these 2 groups). Interesting that almost 1/4 (21%) thought the test was "easy" - it'll be interesting to see later if this confidence leads to accurate identification!

Finally, what you've all been waiting for:

WOW! Remember that Set B was the MP3, yet for those who picked A or B, most thought A sounded inferior! Looking at just the ones who selected A or B, assuming a 50% chance of success in a "guess", the fact that only 45 respondents got the answer correct out of 123 is statistically significant with a probability <1%.

Let's have a look at those who were confident and said this test was easy:

As you can see, despite the confidence, most of the respondents thought that Set A (the original lossless audio) sounded worse than Set B (MP3).

How about those with more expensive equipment vs. less expensive?

For those who used equipment $6000 and above, we see a similar distribution of preference for Set A, but look at what happened to the proportion for those using less expensive equipment. It appears that those using <$500 actually showed a more balanced preference of A and B - it seems like the participants with more expensive equipment preferred the lossy tracks.

Looking at the larger groups, it was interesting to see that those who used speakers (either floorstanders or bookshelves) seem to prefer Set A more than headphone users (likely not significant but interesting observation):

As for the songs themselves, the song "Keine Zeit" where the lossy file measured with the most variance compared to the original lossless file (ie. the song most difficult to encode resulting in the most error), was the one where most preferred the sound of the MP3!

In contrast, the other 2 songs were slightly more balanced. Note though that since songs were grouped as "sets", these results are obviously not independent of each other.

Surprised by the results? I sure was!

Continue to - Part III: Discussion