Lately, I’ve been working with Scott Wilkinson over at AVS Forum to create a quasi-meaningful test to determine whether people with very good playback systems can “perceive” the difference between a bona fide 96 kHz/24-bit track and the downconverted 44.1 kHz/16-bit version of the same track. We’ve just about ready to launch the thing as soon as the technical people at AVS Forum figure out the right place to put the test files. This is certainly not going to be the rigorous test that I’m planning but we thought it would be interesting to let readers participate in a survey that actually could provide some useful feedback.
I’ve seen a number of surveys lately the attempt to determine whether people can “hear” the difference between high-resolution audio and standard compressed files or the difference between 16 and 24-bit audio. But just as the Boston Audio Society study failed because none of the content evaluated during their study were real high-resolution audio, the current surveys are using content downloaded from the web that says that it is high-resolution but in reality isn’t. So Scott and I decided to try a similar test using a few of my recordings that actually do have ultrasonics and dynamic range in excess of standard CDs.
I pulled three tracks from my catalog. There’s the “Mosaic” track that I’ve shared repeatedly with readers, a track from Steve March Torme and a big band that has a dynamic range above 100 dB as well as ultrasonics AND a track by trumpeter Wallace Roney and his band playing with a Harmon mute, which produces lots of energy above 20 kHz.
The plan is to provide these tracks at 96/24 and 44.1/16 and let users compare them using the ABX methods provided by Foobar (PC) and ABX Tester (Mac). He’s written up the whole thing and will launch it on AVS Forum very shortly. I have the spectrograms and audio as well and will make them available as soon as the thing goes live on AVS.
But in the midst of preparing the files, I downloaded the ABX Test app for my Mac to check out how it works. The program allows you to associate “A” and “B” audio tracks with the program and then randomly builds 5 “X” items. You can listen to “A” or “B” as many times as you want from anywhere in the track and then listen to the “X” item. Based on what you hear, you choose whether you believe the track is the “A” or “B” version.
So I took the test myself yesterday. The first track that I plugged in to the ABX Tester was the “On the Street Where You Live” by Steve March Torme. This track has a tremendous dynamic range and lots of ultrasonics. I know that the last 40 seconds contains the highest dynamic range so I concentrated on that section as I did the test. I listened to all 5 “X” items and made my choices.
The system I used consisted of my tower Mac connected via USB to a Benchmark DAC1 to a set of Oppo PM-1 headphones. I didn’t really go to any effort to maximize my situation…after all I just wanted to check out the ABX Tester app. But this equipment is more than capable of delivering great reproduction.
To my utter disappointment and complete surprise, I failed miserably to correctly identify the high-resolution version. When I clicked on the “Check Answers” button, the window popped up and told me that I got 0% right. My instantaneous reaction was complete shock. I could see my life’s work going down the toilet.
Then I thought a moment. The fact that I got them ALL wrong, merely indicated that I swapped the high-resolution and standard resolution files during the test. Getting 0% is the same as getting 100%! I was able to distinguish the difference between the two files every time…I simply reversed the “A” and “B” source files.
Even after this realization, I was genuinely surprised that I scored a perfect 0%. It’s true that I know what to listen for and clearly heard the difference in my tracks…but I didn’t think I would get this results the first time out.
You can do this today with the “Mosaic” track that is on the FTP site. Download ABX Tester and try it yourself. Can you get 5 out of 5? I did…and I’m an old man with aging ears.