I guess: Perception
One simple, clever method (don't know if I read it in Earl's papers): measure harmonic distortion, and multiply with 2*pi*f (thats a differentiation in the time domain, transformed in the frequency domain). This way, higher order harmonics have a much higher weighting than lower order harmonics. Higher order harmonics are much easier to hear because they're not masked by the fundamental.
One simple, clever method (don't know if I read it in Earl's papers): measure harmonic distortion, and multiply with 2*pi*f (thats a differentiation in the time domain, transformed in the frequency domain). This way, higher order harmonics have a much higher weighting than lower order harmonics. Higher order harmonics are much easier to hear because they're not masked by the fundamental.
I am very surprised that you are unaware of this work.
There is no correlation between the measures of THD or IMD and perception. This has been proven on many occasions by more than just Lidia and I.
To yield a high level of correlation one must look at nonlinearity differently than just THD or IMD. Our metric was one way, there may be others, but the bottom line is that these correlations have to be proven, not just assumed (as THD and IMD have been).
So we still live in a bizarre world, decades on, where it's obvious that distortion causes sound quality problems, yet the level of investigation into this is occurring at a quite pathetic rate: most of the effort to "improve things" thrashes away at frequency response and reflections as being magic bullets, which they will never be ...
The degree of "laziness" and inertia in this field is quite remarkable ...
The degree of "laziness" and inertia in this field is quite remarkable ...
------------------
Paul Klipsch argued that IMD was not only audible but perceptually quite aversive. I think he knew a thing or two about audio.
I have noticed that a lot of the audiophile/high end audio, does seem to consist of declaring that arbitrary and possibly imaginary factor/phenomena X is a dire threat to your audio quality and that their product/secret sauce will magically protect you from it.
I really lost my respect for these sorts of people when they started claiming that a dot from a green magic marker could dramatically improve the sound quality of your CDs....
The charlatans largely exist because the work hasn't been done, by researchers sufficiently adept, to clearly define what contributes to SQ in all the meaningful areas and aspects. Charlatans essentially don't exist in the video field because the development work has been thoroughly and forcefully done to push the boundaries in the important, significant parameters - there's little manouvering room left for people out to make a quick buck in the visual media.
The fact that YOU don't understand and aren't educated about this, doesn't mean everyone else isn't. This hasn't been the 1960s for quite some time now.
There's been a LOT of research and improvements in knowledge, skills and manufacturing when it comes to audio.
We have these things, called "Computers" (no not the guys who do math for you). You can right this moment buy a "Computer" and a "Microphone" which will work together to give you just about all the information you could want about audio signals. They can display them in all SORTs of pretty ways and with all sorts of analysis.
In fact we can combine the two and even attempt to use that information to minimize the effects of the room on an audio signal.
If I thought you weren't simply yanking our chain with these ludicrous statements, I'd bother to explain this to you too. As is I'll leave you with just one example.
$2,200 HDMI cable
Sorry, this is not what I'm talking about. That "pretty" information does not clarify the subtleties that cause the sound to work, or not work, in a quality sense for many people. Yes, some people are more sensitive to lower level defects in the sound than others, but that should not prevent the research being done to understand what causes those issues in the sound, and resolving them. Just saying they don't exist as an audible problem for a major segment of listeners, the less critical shall we say, is not good enough ...
The fact that some of the most highly regarded audio systems are based on technology that's 50, 60, 70 years old should give the game away. Engineering that is that "primitive" gets key things right, that the latest and greatest components don't achieve for a large number of listeners. Or do listeners have to be trained, conditioned to "understand" and appreciate that the modern audio is correct, because our measurements are telling us so ...
Missing the point: where are the ads for a 12" B&W round CRT TV which will deliver "videophile" quality picture? You did note that I used the words "essentially" and "little" - I wasn't absolute in my statements - didn't you? ... I didn't box myself in entirely ...
The point is, that the video componentry is based on the latest thinking and developments by large corporations, and not filled with kitchen style engineering from enthusiasts. When was the last time you saw ads for someone to mod your TV, tinker with the internals to "fix" the deficiencies left by the manufacturer?
The fancy cable companies just see a handy offshoot appearing and take advantage of that, using their "reputation" from the audio world; these companies wouldn't exist if there weren't audio "issues".
Last edited:
Earl, here's an article that might be worth a read: Klirrfaktor - wie viel ist zu viel?
It's from a german DIY online magazine, unfortunately all results are only available for customers. Summary: they took the Zwicker masking curves (ISO 532), developed a program that calculates the masking effects and created many curves of distortion vs. frequency vs. level. At the bottom of the page is an example for F2 (K2 in german). The results show good correlation to those found out by intensive practical testing.
It's from a german DIY online magazine, unfortunately all results are only available for customers. Summary: they took the Zwicker masking curves (ISO 532), developed a program that calculates the masking effects and created many curves of distortion vs. frequency vs. level. At the bottom of the page is an example for F2 (K2 in german). The results show good correlation to those found out by intensive practical testing.
I don't mean I really have such an amplifier, but if I did, would the fault show up in a test, or might it be one of those cases where a 'golden ears' would spot it, but the tests draw a blank? i.e. an inherent sonic characteristic that can't be measured?
It would absolutely show up in testing, at least if you do the sort of testing that engineers do (e.g., look at impulse response into reactive loads, look at overload recovery...) rather than the cartoon measurements (THD at one frequency and power only, using a resistor load) beloved of the irrational crowd.
Yeah, too bad it's in German and restricted. I'll talk to them, maybe they'll provide a translated version. But the analytical approach is quite impressive to me.
It looks a lot like the approach that we used, except they are looking at standard THD measurements and how masking would affect those (from what I could tell) and we looked at a new measurement that used the same masking philosophy. They showed % audibility versus frequency at different SPLs, but I have to assume that the % was THD. That's fine as long as the shape of the non linearity does not change, but it will fail if the shape does change. That is the point of what we did. You cannot just look at a symptom of the nonlinearity like THD and IMD does, you have to look at the nonlinearity itself because different shapes can have the same THD and sound dramatically different. It is the shape that counts. THD does not account for shape in any way. It is blind to the most audible aspects of the problem.
I"m aware of a lot of work on distortion going back to the 1920s, I've read some of your papers, too. Most of the work I know shows that a single percentage number for distortion doesn't tell you the audibility, you have to know more about the harmonic structure and other details to know how audible the distortion is.
I assume that's what you meant in your post, but was not sure, so I asked.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.