The reason FFT data comes out as per-Hz bandwidth is because that's just how the underlying code works. Likewise for similar processes like software broadband noise reduction. But that's not how audio and music work inherently. As I've explained twice now, everything in audio is ratios. You can also add to my other examples the fact that musical intervals are ratios too.
Kidding aside, that's all great - lots of things are ratios. But expressing certain things as percentages can be misleading in audio. That's all I was getting at. Express an SPL change as a percentage and you're likely going to confuse someone. (Hopefully stating the obvious: Decibels are an expression of a ratio, they are not a percentage.) Expressing bandwidth as a percentage is less common, in my experience, than expressing it in terms of frequency.
Likewise, expressing a measured frequency error as a percentage when (a) the source of the error is completely unknown and (b) there is absolutely no indication that the observed error at one frequency is indicative of a constant percentage error for other frequencies is grounds for confusion. It could be a fixed percentage, but our collective experience tells us (me?) that that is highly unlikely. It could be a fixed error in terms of frequency, which would grow more and more meaningless as frequency increased. (What I believe:) It could be an anomaly that can be explained away by something else entirely.
Which brings me to a final point: Why don't we stay on track with figuring out wtf is going on instead of carrying on this BS percentage discussion.
Quote:
Hang in there, with my expert guidance you'll get it eventually...
I'm sure I will...±20% of it, anyway...
_________________ ---lovecow---
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David French Respected Past Moderator
Joined: Jun 19, 2002
Posts: 2852
Location: Indiana
Likewise, expressing a measured frequency error as a percentage when (a) the source of the error is completely unknown and (b) there is absolutely no indication that the observed error at one frequency is indicative of a constant percentage error for other frequencies is grounds for confusion. It could be a fixed percentage, but our collective experience tells us (me?) that that is highly unlikely. It could be a fixed error in terms of frequency, which would grow more and more meaningless as frequency increased. (What I believe:) It could be an anomaly that can be explained away by something else entirely.
That's exactly the problem with the use of percentages here. The ammount of error is due to something that likely does not operate in terms of percent.
Jeff wrote:
Which brings me to a final point: Why don't we stay on track with figuring out wtf is going on instead of carrying on this BS percentage discussion.
That is exactly what I was about to say.
So who has an idea for how we can design an experiment to prove beyond a shadow of a doubt that tangentials can be a significant problem or can prove the cause of the error?
proudtower Recording Org Pro Audio Forums
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Ethan:
"Showing frequency response on a linear scale is rare"
Low frequency data are OFTEN presented on a lineair scale.
Our ear works lineair for low freq's.
And even in that poor acousticians bible, the master handbook of acoustics, low freq TEF waterfalls are on a lineair scale
Ethan Winer Respected Past Moderator
Joined: Mar 19, 2001
Posts: 3209
Location: New Milford, CT USA
> Express an SPL change as a percentage and you're likely going to confuse someone. <
By percentage all I meant was things that are ratios, versus absolute units. Obviously nobody will express an SPL change as a "percentage" and will use dB instead. But dB is a ratio. That's all I meant. I assumed you knew that.
> Expressing bandwidth as a percentage is less common, in my experience, than expressing it in terms of frequency. <
Then you have some mighty funky experience. Bandwidth is a ratio based on the center frequency. No engineer expresses bandwidth in terms of Hz. Indeed, the very definition of Q is a ratio that's related to the center frequency.
> Why don't we stay on track with figuring out wtf is going on instead of carrying on this BS percentage discussion. <
And why do we choose one scale over another? So we can see a given phenomenon better. We are identifying resonances here, so linear is better. This research is for now complelely disregarding human perception. We are studying physics.
But, this is another one of those BS discussions that are so secondary to the issue at hand.
So who has an idea for how we can design an experiment to prove beyond a shadow of a doubt that tangentials can be a significant problem or can prove the cause of the error?
Well, that's all about perspective, isn't it? I already believe beyond a shadow of a doubt that if you excite a room with sound, it will "ring" at the modes. How much or how little at what frequencies is totally dependent on the exact situation. Most studio rats are seeking to take as much of the room out of the equation as they can. Whether or not the {1,2,0} tangential mode is actually causing any specific problem is far less relevant that what actually can reasonably be done about it...and all the other problems. If I might bring Rod's wisdom into this thread, you have a choice there. Either:
• Build your walls out of rice paper in a much larger space. Or outdoors.
OR
• Treat the room as much as you can for all the possible problems and call it a day.
If you're going to build the best possible room, hiring someone to help you achieve that is the best option.
If you're trying to fix a small bedroom, basement room, attic room, garage room, etc. and you're stuck with what you've got - most people here at RO (including me) probably qualify for that - then treat the room with your favorite flavor of acoustical treatments and record/mix to your heart's content.
Getting back to your question, I would like to say for what seems like the dozenth time that there is no finite test that can be performed that will give any sort of closure to this "importance of 'non-axials'" question. With all due respect to all participants, this is whole "issue" came about as a result of one mode calculator and its relative validity. Instead of trying to solve that problem - rename the calculator, update the calculator, ignore the calculator - some felt it a more worthy cause to question something that doesn't need to be questioned. IMHO, anyway.
While the motives are admirable, I simply feel the continued search for a problem that doesn't exist is not a good use of our collective time. It's like bickering with a cop: The cop says you were doing 80 mph in a 55 mph zone, yet you know you had the cruise control set at 78 mph. Either way, you're going to get a ticket!!! (But hey: What if the cop's radar and/or your speedometer are off by ±20%. Well, Sparky, that still means you could have been doing around 116 mph. Andohbytheway, you're still getting a ticket.)
So. My short answer is "I don't care." Despite the best efforts to bring the full picture into focus for some, they are still unconvinced. We can certainly continue to beat this to death. But we're digging for treasure that we aren't even sure exists. And if we find it? Well, remember Geraldo and Capone's treasure and live TV? I think that's exactly where this whole thing is going. All hype with a big, fat, well-publicized anticlimax at the end.
There are people out there waiting for me to help them. David, whether some people are convinced of something or not despite our best efforts now becomes less a question of finding more ways to convince and more about questioning why we're still trying to convince.
Adios!!!
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Ethan Winer Respected Past Moderator
Joined: Mar 19, 2001
Posts: 3209
Location: New Milford, CT USA
Great summary. It really doesn't matter whether a particular room and speaker / listener placement excites these modes or those because the solution is almost always the same: Broadband absorption that works to as low a frequency as possible.
I see your points Jeff, but for me, this has moved beyond an 'applications' point of view and into an interest in pure physics. If I am alone in this, so be it.
By percentage all I meant was things that are ratios, versus absolute units. Obviously nobody will express an SPL change as a "percentage" and will use dB instead. But dB is a ratio. That's all I meant. I assumed you knew that.
I should have mentioned that...oh, wait...I did. Something above about "stating the obvious."
Quote:
> Expressing bandwidth as a percentage is less common, in my experience, than expressing it in terms of frequency. <
Then you have some mighty funky experience. Bandwidth is a ratio based on the center frequency. No engineer expresses bandwidth in terms of Hz. Indeed, the very definition of Q is a ratio that's related to the center frequency.
Nice. Typical bait and switch. You are the master. Look at Chapter 15 of Everest. Show me where he's referring to modal bandwidth as a percentage.
_________________ ---lovecow---
"You've got to be very careful if you don't know where you're going, because you might not get there." - Yogi Berra
I see your points Jeff, but for me, this has moved beyond an 'applications' point of view and into an interest in pure physics. If I am alone in this, so be it.
I'm not saying I'm abandoning you. I just don't know how much more we need to put up on the board here. Are 3 examples enough? 30? 300?
I will absolutely continue in the discussion from the physics perspective you're talking about. But until someone can come up with something probable that shows our understanding of modal response is questionable, I think our work here is done!
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David French Respected Past Moderator
Joined: Jun 19, 2002
Posts: 2852
Location: Indiana
What exactly is out understanding of modal response? Is there an argeement on what accepted theory is?
Again, from my perspective, yes there is agreement. There always has been. Like I said, excite a room with sound and you will see the room "ring" at the modes. While this might be taking all the physics for granted (which seems to me to be an inherent contradiction in terms), if one takes the time to predict a modal response, one can find agreement with the measurements.
How much or how little agreement is going to vary.
How much variation will be different for each application.
Agreement and variation and applicability are, in their own right, dependent on many things.
I have shown at least two examples where mode prediction agreed with what was measured. You have shown one. Again, how much or how little they agree are debatable. Is it open to interpretation? Sure. Everything is. Are the examples rigorous in their "proof"? No. We have to assume that the people that require proof know something about what they're asking us to proove. And I assume that is the case. Thus, I feel the results thus far are showing exactly what needs to be shown. That is, one can predict modes and find correlation with measurements. Is this proof that one mode or another are problems? No. For that, the "after" would have to be looked at. And even then, we might get more questions than answers.
And are any of the above examples - or any future examples - going to tell us about the relative importance of this mode or that mode? No. IMO, the sort of "ranking" some folks are looking for doesn't exist.
Am I making sense?
_________________ ---lovecow---
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