On June 2, Tyler Fisher and Jacob Ganz asked a very real question on the NPR Music website “How Well Can You Hear Audio Quality?” If you haven’t taken the test, head over to NPR.org and check it out. The authors selected 6 different music selections, extracted a short (10-20″) excerpt, encoded them at 128 or 320 kbps in the MP3 format, and left them in the “uncompressed .WAV format”. Users can play each of the excerpts and then choose which one is the highest quality.
The introductory paragraph provides the catalyst for the quality quiz:
“Recently, the rapper Jay Z relaunched the subscription streaming music service Tidal, which includes the option to listen to high-definition audio for $19.99 per month. Tidal’s HiFi, with its uncompressed audio files, promises a better listening experience than any other streaming service on the market.”
The claim that Jay Z’s TIDAL site is offering “high-definition audio” streams is wrong on two counts…and that’s only the first sentence. A brand as respected as NPR should refer to “high-resolution audio” NOT “high-definition audio” and they should know that streaming 1411 kbps CD specification audio is not high-res, even by the lame standards insisted on by the DEG, CEA, NARAS, JAS, and major labels. The writers didn’t get off to the best start…and there are other problems, as we’ll see.
The actual quiz is lacking in a number of important ways. The most significant is the fidelity of the recordings that are offered. As you’ll see shortly, most of the tracks are heavily mastered and none of the uncompressed .WAV files qualify as HiFi quality. And then there’s the problem of presentation. When I do comparisons in my studio, I always allow the person being tested to instantly and noiselessly switch between the two options. Most of the time these test are performed…and in the present NPR case…you get to listen to a selection from the beginning and then listen to another choice “from the beginning”. This means you have to rely on your “musical memory” instead of a direct comparison. It is really hard to succeed at a test like this.
I got 3 out of 6 correct sitting here at my computer listening through my Oppo PM-1 Planar Dynamic headphones from a Benchmark DAC2 DAC…I had a very good signal path!
The order of the tracks and formats are randomized so you can’t game the test. The first example that came up was the classical selection by Murray Perahia & The English Chamber Orchestra.
Figure 1 – The NPR hearing quiz Murray Perahia selection and accompanying text.
I read the accompanying text and was surprised to see this was “released in 1981” because the first commercial disc wasn’t produced until a year later. Billy Joel’s 52nd Street with the first album to be released on CD along with the Sony CDP-101 CD Player (which came out on October 1…thus the 101!).
I missed this one. When I looked at the spectrogram (I recorded all of the examples following the test), I didn’t feel too bad. Take a look at the spectra below:
Figure 2 – The spectrogram of the Murray Perahia selection on the NPR test. [Click to enlarge]
This was a very early digital recording intended for the new CD format. The recording was done at 44.1 kHz and 16-bits. The music is pretty quiet and not highly dynamic. The excerpt doesn’t contain much musical information above 10-15 kHz. And the information that is up in that register is down 85 dB below the peaks. This means that a person would have to be able to hear very subtle musical harmonics 85 dB below the normal level of the music in order to get this one correct. There are other subtle distortions contained in the MP3 files but a 320 kbps encode fooled me.
The MP3 files have no high frequencies above 16 kHz…and the uncompressed WAV files has energy up there but no music. Not the best piece to test with IMHO.
I’ll dissect the other 5 tracks tomorrow, so stay tuned. I’d love to hear how you did and the equipment you used when taking the test.