Jean-Pierre Côté's dashboard

Jean-Pierre Côté asked a question in SuperMegaUltraGroovy on June 30, 2008 19:37:

Export a TF to import as Cal file?

Hi,

When exporting a frequency graph’s data as txt, the file as 2 columns, the 1st being frequency and the second, dB (starting on line 2, separated with commas, using “.” as decimal).

This file can be imported as a mic calibration file by Fuzz. Is this operation going to adequately subtract the first TF from any new measurement?

In other words, what, exactly, is the format for mic cal files, and can Fuzz generate such files...?

Jean-Pierre Côté replied on June 30, 2008 19:25 to the question "THD" in SuperMegaUltraGroovy:

Well, in my understanding, with a SR of 32 kHz, for instance, you cannot measure harmonic distorsion above 8 kHz, indeed... But you wouldn’t hear it either since any harmonic distortion components would be filtered out by the AD.

From Müller’s paper, I understand 2 possible reasons for this frequency shift: The first is that it’s a (proposed) convention, in which case personally I don’t agree with it as it’s counter intuitive since you cannot easily relate the harmonic component to its fundamental. The second comes from “After this operation, the shifted spectrum can be divided by the fundamental spectrum, yielding the frequency-dependent distortion fraction”(p47). I don’t understand why this would be, but it would be the way to calculate the HD percentage ...

BTW, it’d be great if Fuzz would perform that calculation as well...

A comment on the question "Can you recommend basic hardware kit for FuzzMeasure?" in SuperMegaUltraGroovy:

Eathworks now also have the M23 as lowest priced measurement mic. – Jean-Pierre Côté, on June 30, 2008 18:44

Jean-Pierre Côté replied on June 25, 2008 15:09 to the question "THD" in SuperMegaUltraGroovy:

Thanks Thend. The image provided there is from a very “linear” system. It sems to me that It’s much more difficult (read “impossible”) to measure the distortion this way on complex IR’s.

Do you simply calculate the ratio from the power of the “distortion spark” over the main impulse?

One more thing, Thrend: You write that, using this way of measuring distortion, you don’t add the reverb’s distortion. But if you measure the acoustics of a room, you do want that distortion (I know I do)...

Can you point me to any literature about this?

Also, Chris, aren’t the distortion curves shifted to the left while they should be to the right? For instance, H2 should be fH1 X 2, but it appears to be fH1 / 2 in Fuzz’ graphs... Or am I not reading this correctly?

Jean-Pierre Côté replied on June 20, 2008 19:56 to the question "THD" in SuperMegaUltraGroovy:

Thend, can you explain the manual method you use that involves “selecting the IR distortion” ?

Jean-Pierre Côté asked a question in SuperMegaUltraGroovy on June 20, 2008 16:32:

THD

Hi Chris,

I’ve been playing around with the new harmonic distortion graphs. Great feature.

Questions :

- When an IR is normalized, the distortion graphs do not follow the signal (H1). In order to check the difference in level between H1 and the others, I presume it is the non-normalized presentation that’s good?

- I need to get a single number qualifier for distortion (or, at least, per distortion order). I realize THD is traditionaly measured out of a single frequency, but it does seem possible to get the ratio of the total level of added harmonics over the fundamental for the whole spectrum. We could use either averaged level or sum... Is this already implemented in any way in Fuzz? Anybody here knows if this is an officially developped technique for qualifiying THD?

- How about adding the level of H2 and H3 to the export data so we could play with this by ourselves on a spreadsheet?

- Any plan to add more harmonic orders?

Jean-Pierre Côté replied on June 13, 2008 19:32 to the question "Minimum phase?" in SuperMegaUltraGroovy:

Thanks Chris.
But no this is not what I meant. Sorry for the confusion.

By T, I mean EDT, T20 or T30... I still can’t figure out why the reverse FFT of the real part of the FFT yields to more (better?) reverberation time measures...

Jean-Pierre Côté replied on June 12, 2008 15:06 to the question "Minimum phase?" in SuperMegaUltraGroovy:

O.k. Thanks. I’ll need help from my matlab savy friends on this one...

Meanwhile, when there are differences between the original and the min phase copy of an impulse, which one is right? For instance, T can be slightly or very different from one to the other. Which one is closer to the actual T of the room (or system)?

Jean-Pierre Côté asked a question in SuperMegaUltraGroovy on June 12, 2008 01:31:

Minimum phase?

Hi Chris. Can you be more specific about what minimum phase copies are? The online help says : “It will minimize the phase components”. What does this mean?

Jean-Pierre Côté replied on May 26, 2008 14:25 to the question "Any plans to implement C50 in Fuzz?" in SuperMegaUltraGroovy:

I have the paper too but not the skills to program that kind of stuff... Tell me if I can be of any help.

About the T, I think I preferred v.2... To make it better (for the way I use it anyway), I suggest 3 buttons on top of the window (EDT, T20, T30), and the graph would show the data of any button that is selected, may it be 1, 2 or all of them. Oh, and make the 3 graphs more distinct in colour.

A nice feature (especially for students) would be to have an envelope line along with the time domain graph in the main app that would show the decay as per the result of the T calculations.

About the plugin business, I was just trying to make the work worth it for you. My guess is that intelligibility measures are very specialized, and that those who need it would probably be willing to pay extra for it.

While we’re at it, RASTI would be great. But you need a special ref signal owned by B&K and you’d probably have to pay to get the right to use this...

RASTI is more widely used that C50 &co (at least in North America).

Jean-Pierre Côté replied on May 26, 2008 14:07 to the problem "v3 : Markers in Impulse graph have a weird behaviour (bug)" in SuperMegaUltraGroovy:

We (students and I) work on a window of about 100 to 15 ms. We identify the time of arrival and strength of specular reflections and correlate these with the combs in the fr graph.

BTW, the rss feed did not notify that you answered...

Jean-Pierre Côté reported a problem in SuperMegaUltraGroovy on May 22, 2008 17:21:

v3 : Markers in Impulse graph have a weird behaviour (bug)

While markers work A-1 in the frequency graph, they’re almost unusable in the impulse graph. Once created, you get stuck with the pointer as a close hand, and anything you try to do from there seems to be kind of one click late... Moving the markers’ position is very difficult, so is removing it.

Jean-Pierre Côté asked a question in SuperMegaUltraGroovy on May 22, 2008 17:11:

Any plans to implement C50 in Fuzz?

Hi Chris,

Since you already have EDT and T as per ISO 3382, would you consider adding C50, C80 and D50 measurements? That would be great for acousticians (or anyone with a room where intelligibility is an issue)! Maybe in the form of a plugin that could be sold separately...