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With all the popularity and various manufacturers seeming to test the water for High Resolution Audio support I thought this might be a good time to study whether there is truly any benefit to high resolution audio.

For your reading pleasure I submit an article by a very respected Engineer in the software industry. You all know of his and his organizations contributions to the thing we love.... namely Audio. You won't know him by name but I guarantee that all of us at some time or another have used the products of his labor.

Chris Montgomery (ziphmont) is largely responsible for some of the various Audio codecs that we all enjoy. Most notably, the FLAC encoder / decoder. He is a MIT Graduate in Electrical Engineering and Computer Science and has a Master of Engineering degree from Tokyo Institute of Technology. Suffice it to say he is no lightweight.

Here is his article regarding High Resolution Audio. Please read the article before commenting and evaluate the data yourself.

Link

We are "hardware" limited, meaning due to our physical auditory makeup by design we have an upper limit of hearing at 20-22kHz
  • Much like we cannot see in the Infrared spectrum because we don't have the physical makeup to do so.
In summary, it's not certain that intermodulation from ultrasonics will be audible on a given system. The added distortion could be insignificant or it could be noticable. Either way, ultrasonic content is never a benefit, and on plenty of systems it will audibly hurt fidelity. On the systems it doesn't hurt, the cost and complexity of handling ultrasonics could have been saved, or spent on improved audible range performance instead.

Understanding is where theory and reality meet. A matter is settled only when the two agree.

Empirical evidence from listening tests backs up the assertion that 44.1kHz/16 bit provides highest-possible fidelity playback. There are numerous controlled tests confirming this, but I'll plug a recent paper, Audibility of a CD-Standard A/D/A Loop Inserted into High-Resolution Audio Playback, done by local folks here at the Boston Audio Society.

Unfortunately, downloading the full paper requires an AES membership. However it's been discussed widely in articles and on forums, with the authors joining in. Here's a few links:

The Emperor's New Sampling Rate
Hydrogen Audio forum discussion thread
Supplemental information page at the Boston Audio Society, including the equipment and sample lists

This paper presented listeners with a choice between high-rate DVD-A/SACD content, chosen by high-definition audio advocates to show off high-def's superiority, and that same content resampled on the spot down to 16-bit / 44.1kHz Compact Disc rate. The listeners were challenged to identify any difference whatsoever between the two using an ABX methodology. BAS conducted the test using high-end professional equipment in noise-isolated studio listening environments with both amateur and trained professional listeners.

In 554 trials, listeners chose correctly 49.8% of the time. In other words, they were guessing. Not one listener throughout the entire test was able to identify which was 16/44.1 and which was high rate [15], and the 16-bit signal wasn't even dithered!

Another recent study [16] investigated the possibility that ultrasonics were audible, as earlier studies had suggested. The test was constructed to maximize the possibility of detection by placing the intermodulation products where they'd be most audible. It found that the ultrasonic tones were not audible... but the intermodulation distortion products introduced by the loudspeakers could be.

This paper inspired a great deal of further research, much of it with mixed results. Some of the ambiguity is explained by finding that ultrasonics can induce more intermodulation distortion than expected in power amplifiers as well. For example, David Griesinger reproduced this experiment [17] and found that his loudspeaker setup did not introduce audible intermodulation distortion from ultrasonics, but his stereo amplifier did.
 

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Just listened to the latest SQology podcast and Benny z and Andy Wehmeyer discussed this very thing starting around the 30 min mark.

Absolutely great discussion on a lot of things with Andy. Looking forward to part 2. Anyhow, Andy referenced that he did a post on this in his Tech tips forum in the podcast so I went to see what he had posted.

https://www.audiofrog.com/community/tech-tips/tech-tip-digital-audio-basics/

Interesting that he seems to have come to same conclusion.
 
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