03-Apr-2019, 10:44
I acknowledge that the comparisons/tests/studies that have been done comparing high res to CD quality have been equivocal in their outcome. Some have supported the existence of a difference, some haven't. I used to work in health and safety before I retired and one thing I learnt over time, looking at studies relating to possible health related effects from various sorts of exposure to possible substances and radiation with supposed adverse effects, is that it is extremely hard to design and conduct a high quality study that delivers results that are easily repeatable. People make claims on both sides of the argument and all provide observations to support their view and conduct various sorts of studies but then when those studies get analysed problems with the study design or conduct often come to light which end up casting the results in doubt. That sadly is the case with a lot of the disputes in audio and it's all to easy finding evidence that doesn't support the conclusions which then get drawn from it, and that's for the evidence produced on both sides. Sloppy work isn't confined to one side of any argument.
One obvious problems with studies like the Waldrup one is the fact that every person who responded listened using different equipment and there was no control on the quality of the equipment. If there is a difference there's no way of telling what proportion of participants listened on equipment that was capable of revealing the difference. That's one of the reasons why high quality studies are conducted under controlled conditions in which each listener not only listens to the same tracks but listens to those tracks played on the same equipment and that equipment is selected to ensure, as far as possible, that the equipment used is not going to mask any difference. Good quality studies aren't easy or quick or cheap to conduct and analysing the results properly is another problem area.
I'm not saying Waldrup's results are wrong but I am saying that his test design and procedure don't stand up to professional levels and that means that care has to be taken with the interpretation of the results. As for the results he reports, they're couched in anecdote, they don't include statistics of the number of correct responses vs incorrect responses, and most importantly they avoid any mention of whether any individuals managed to get everything right. If some people did get everything right, one would want to know what the circumstances, including their equipment choices, of their comparisons were and how those circumstances differed from those of the people who didn't do as well. If everyone listened under identical conditions and with identical conditions to anyone who got everything right, would the results of this survey be different? Good quality tests are not easy to design and conduct.
In any event, that issue is different from the point I made which was simply that saying we can't hear anything above 20 kHz so frequencies above that can't affect what people hear is incorrect because intermodulation of frequencies above the audible range can and does produce effects within the audible range. Intermodulation requires 2 or more simultaneous tones and tests which determined the limits of our hearing range were made with single tones so intermodulation effects don't occur. Simultaneous tones are a significant feature of music and can't be ignored. If you're going to test whether or not frequencies above 20 kHz affect what we hear when we're listening to music you have to conduct tests which use simultaneous tones if you want to have some hope of being able to generalise your results to what we can hear when listening to high res music sources. Even if we can hear intermodulation products from tests using simultaneous tones which includes a tone above 20 kHz in conjunction with another tone in the audible range that still won't guarantee that we can hear differences between high resolution music and CD quality music sources because music is much more complex than simple combinations of 2 different tones but you would learn things about how to set up a test using actual music from conducting tests using 2 tones that would help to design and set up higher quality tests using more complex sound sources including music.
My point, as I said, is that the question isn't as simple as it appears. I haven't seen any reports of a test or study that I think produces really convincing results for or against there being audible differences between high res and CD quality sources. Designing such a test or study isn't going to be a simple task and conducting it is also not going to be easy, and the test would have to be conducted under carefully controlled conditions because good studies have to be capable of being replicated by other researchers and consistently delivering the same result.
One obvious problems with studies like the Waldrup one is the fact that every person who responded listened using different equipment and there was no control on the quality of the equipment. If there is a difference there's no way of telling what proportion of participants listened on equipment that was capable of revealing the difference. That's one of the reasons why high quality studies are conducted under controlled conditions in which each listener not only listens to the same tracks but listens to those tracks played on the same equipment and that equipment is selected to ensure, as far as possible, that the equipment used is not going to mask any difference. Good quality studies aren't easy or quick or cheap to conduct and analysing the results properly is another problem area.
I'm not saying Waldrup's results are wrong but I am saying that his test design and procedure don't stand up to professional levels and that means that care has to be taken with the interpretation of the results. As for the results he reports, they're couched in anecdote, they don't include statistics of the number of correct responses vs incorrect responses, and most importantly they avoid any mention of whether any individuals managed to get everything right. If some people did get everything right, one would want to know what the circumstances, including their equipment choices, of their comparisons were and how those circumstances differed from those of the people who didn't do as well. If everyone listened under identical conditions and with identical conditions to anyone who got everything right, would the results of this survey be different? Good quality tests are not easy to design and conduct.
In any event, that issue is different from the point I made which was simply that saying we can't hear anything above 20 kHz so frequencies above that can't affect what people hear is incorrect because intermodulation of frequencies above the audible range can and does produce effects within the audible range. Intermodulation requires 2 or more simultaneous tones and tests which determined the limits of our hearing range were made with single tones so intermodulation effects don't occur. Simultaneous tones are a significant feature of music and can't be ignored. If you're going to test whether or not frequencies above 20 kHz affect what we hear when we're listening to music you have to conduct tests which use simultaneous tones if you want to have some hope of being able to generalise your results to what we can hear when listening to high res music sources. Even if we can hear intermodulation products from tests using simultaneous tones which includes a tone above 20 kHz in conjunction with another tone in the audible range that still won't guarantee that we can hear differences between high resolution music and CD quality music sources because music is much more complex than simple combinations of 2 different tones but you would learn things about how to set up a test using actual music from conducting tests using 2 tones that would help to design and set up higher quality tests using more complex sound sources including music.
My point, as I said, is that the question isn't as simple as it appears. I haven't seen any reports of a test or study that I think produces really convincing results for or against there being audible differences between high res and CD quality sources. Designing such a test or study isn't going to be a simple task and conducting it is also not going to be easy, and the test would have to be conducted under carefully controlled conditions because good studies have to be capable of being replicated by other researchers and consistently delivering the same result.
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