There's a lot of interest in "high definition" (HD) audio by both audiophiles and professional recording engineers. Standard CD-quality recording uses a sample rate of 44.1 KHz with a bit depth of 16 bits. Sampling at 44.1 KHz allows capturing frequencies slightly higher than the accepted audible upper limit of around 20 KHz (for young people), and 16 bits provides a very low noise floor 96 dB below the music. Many tests over the years have concluded that nobody can reliably identify CD-quality versus higher resolutions, yet some people still believe that HD audio sounds better, with more realism and clarity. This belief is driven by two myths: 1) ultrasonic freqencies can affect frequencies we do hear, and 2) having 24 bits affords more resolution than 16 bits because there are more vertical "steps" between each sample's volume level. But neither belief is true - ultrasonic frequencies don't interact in the audible range unless distortion is present, and digital audio is continuous without steps. The only thing bit depth affects is the level of background noise.

One potential objection to formal tests by HD enthusiasts is that people are forced to listen through an unfamiliar system in an unfamiliar room. Another objection is they might be stressed from being put under pressure to "perform" while being tested. So I created sample files people can download and play in the comfort of their own environment, to learn if they really can hear a difference between CD-quality and HD audio at 24 bits and 96 KHz. You'll play these files through your own loudspeakers or headphones as often as you'd like, until you believe you can tell which file in each pair is the HD version. This avoids being put on the spot in front of others at a formal blind test, or missing some small detail you might have heard had you been able to play the files a few more times.

For this test I obtained two HD recordings - one is a pop tune and the other a classical piece - and I confirmed that both have content out to the upper limit of a 96 KHz sample rate. I created two excerpts from each for a total of four music fragments about 15 seconds long. Having four samples rather than only one reduces the chance of people guessing correctly, which would skew the accumulated results. I copied each high-def music fragment to a new file, then reduced it to standard 16/44 CD-quality using the audio software Sound Forge. This resulted in four pairs of files. Then I converted the CD-quality versions to 24/96 to make the files in each pair the same size, though that doesn't restore the content lost earlier from reducing the resolution to 16/44. Your challenge is to identify which files in each group are the HD originals, and which are the versions reduced to 16/44. Since there are eight files, I put them all into THIS one 70 MB Zip file to simplify downloading.

Be sure that your playback device supports 24/96 files, otherwise it will downsample the data. Once you believe you know which files are the HD versions, please email me from my Home Page your choices - file "A" or file "B" - for all four pairs of files. If you're unable to tell which files are HD, that's also useful information, so please say so! Eventually I'll have enough data to report the results with confidence, which I'll post on Facebook. If you want to know how well you did, please ask when you email me your choices and I'll tell you how many were correct. Please do not send your choices by PM through Facebook or YouTube. I need replies by email to organize them efficiently. Note that by providing these audio files for download, people could try to cheat by peeking at the file contents rather than listening. So the files were trimmed slightly to random lengths to prevent that from giving a clue, as well as other trickery to hide their identifies.

Ethan Winer has been an audio engineer and professional musician for more than 50 years, and is a principle at RealTraps where he designs acoustic treatment products for recording studios and home listening rooms. Ethan's Cello Rondo music video has received nearly 2 Million views on YouTube and other web sites, and his book The Audio Expert published by Focal Press, now in its second edition, is available at amazon.com and his own web site.

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