Jump to content
The Computer Audiophile

Misleading Measurements

Recommended Posts

1 minute ago, pkane2001 said:


Just a suggestion. 


But it wasn't merely a suggestion, it was also a deflection. So - any evidence?

Share this post

Link to post
Share on other sites

An engineered deflection is still a deflection. So there isn't any?

Share this post

Link to post
Share on other sites
On 7/21/2020 at 3:28 AM, Audiophile Neuroscience said:

Well, I will have to just survive the veiled slurs on my motivations and character #776 #780 #781 but that aside nothing here or in the other dedicated thread changes one inconvenient truth.


In the spirit of an audiophile forum, let's "lift the veils".

Speaking as the writer of #776 and #781, I can tell you that there was no desire to slur your motivation or character, but rather to question your motivation, albeit giving you the benefit of the doubt. I admit "chomps down like a pit bull" seems a slur on your methods - I'm sorry - I should have used "relentlessly persistent", and I regret the offensive tone. 

When it comes to controls and validation, you strongly and persistently argue the case for perfection. What is "perfect" should never be forgotten in discussions of experimental design (or software development). But realizing that in some cases "perfection is the enemy of the good" means often choosing not to halt progress, even if that means good methods over perfect methods.

I have always assumed that the case you argue, even if extreme, is motivated by principle. I would call that "good faith". With that assumption, I expect to see the same argument with those you like and those you dislike. It is clear you dislike Paul.
I assumed a good faith motivation, and that is supported by, IIRC, your never being reticent in describing exactly what you mean and expect in the case of controls. This thread has challenged my assumption, because you don't describe what validation looks like to you, even though that is essential to providing validation.


I understand the need for validation in some cases: it was a big part of my creating a multi-sensory perception model a few years ago. I validated first by defining within which range of stimuli I would test, and then simulating standard published stimuli groups. I compared my model's output to the published perceptual responses; it was not identical, but demonstrated all the necessary features and was considered by others a success. It did not check for out-of-range inputs, so would easily provide GIGO (garbage in, garbage out).
I used Simulink. The MathWorks validated the mathematical performance of Simulink, but would never consider validating it for perceptual models. I had to know what I was asking of it and set the simulation parameters (time step, ODE solver, etc.) correctly. I had to validate my choices myself, and did so successfully.

DISTORT is analogous to Simulink. Paul (and others) have validated the basic mathematical performance, but not whether every person's uses and choices are correct. If you try to calculate your taxes with it, watch out! If you read all of #776, and got past the "good faith" phrase at the beginning, you'll see I offered to validate it for you and document it appropriately, if you spell out what you mean. (I also put the word "reasonable" in there. I won't spend a month on it... all subject to discussion).
Peace 🕊️☮️

Share this post

Link to post
Share on other sites
On 7/20/2020 at 10:56 PM, bluesman said:

When I asked if you'd tested ("validated", a term at which you mysteriously took offense) your app to be sure it was not adding any distortions or other effects besides the desired one, you offered no answer other than that "DISTORT will construct a nonlinearity and that the same non-linearity will generate HD when applied to a single tone, and IMD when applied to multiple tones".  And you may well have said this "at least a dozen times" - I didn't count. 


You also ignored my request for any explanation, no matter how simple, of how you could generate harmonic or intermodulation distortion by adding a nonlinear transfer function to the signal path without producing any other effects on the signal.  Again, you ignored my question and gave the same answer.  Today, SoundAndMotion offered what I believe is a more accurate response - that "...if you want to add anomaly X, you have to be aware that the compression comes with it".  I, too, believe that you cannot add harmonic distortion to a signal without other secondary effects on it, e.g. compression, frequency response alteration, phase shift, etc depending on the exact transfer function used.  BTW, y=f(x) can be a linear equation depending on the function. That’s why I asked how you do what you do with your app.


I still do not understand how you can add a nonlinear transfer function to a signal chain with no resultant change in the signal except the production of harmonic / IM distortion.  You still haven't explained it, if it's even possible (which, from what I know, is not the case).  And compression is only the first unintended "side effect" that came to mind - there are many more. 


I'd hoped to learn something new from you - but that hasn't happened yet.  I still live in hope, but I'm not as optimistic now.  I'm sorry you choose to take umbrage at what I truly think are reasonable questions that are also very relevant to deciding if a measurement is useful or misleading.  


@bluesman, you clearly misunderstand what a non-linear transfer function does and how HD or IMD is produced by audio devices. I suggest you look into it, read about it. Plenty of textbooks, on-line courses, or even simple white papers and tutorials, some even have been mentioned in the new DISTORT thread by others. I'm not going to continue to try to explain the basics to you while being verbally abused.

Share this post

Link to post
Share on other sites
1 hour ago, Summit said:

For me, it is not the measurements that are misleading, it is what they are said to have for actual (SQ) effect that can be misleading. All measurements must be interpreted by someone and interpretations are based on preconceived ideas of what is audible and what is not.



Sure and I think it's Computer Auduophile's position too.


Measurements by themselve are not misleading. People that present them can have hidden agenda or personnal goals different than teachning and sharing neutral informations. There's people who use science badly (we have a couple of exemple here, as well as on ASR forum.


I do agree that we have to do something about this. But removing the data available is not a good solution, this would be a step back.

Share this post

Link to post
Share on other sites
8 hours ago, John Dyson said:

Whether the intermod happens in 'air' or in a 'string', the underlying math is essentially the same as software & electronics emulations of the effects.  I am NOT claiming that precise emulation of the real world is simple, but I don't think that is what we are worrying about.



What we're worrying about is whether recording the interplay of musical instruments, and then replaying that capture "doubles up" on some, nebulous, thing ...


Assuming adequate accuracy of the devices used, the answer is ... that it doesn't.






Over and out.



Share this post

Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

  • Create New...