Psychoacoustics of Room Reflections

amirm · Oct 12, 2012

OK, here at long last, is my article in the last issue of Widescreen Review, summarizing research and listening tests that says our intuition and "common wisdom" about how the room impacts the sound of our speaker is wrong. The focus of this article is on frequencies above the transition (200 to 400 Hz) and relates to the so called "early" or "strong" reflections. It does NOT deal with mid to late reflections. That will be another article

. Unlike my previous article on low frequency optimizations, this article is not an end to end tutorial but rather, sets the stage for the science that governs that. Unless one accepts and comes to term to the view of acoustics here, the other bit won't make sense.

So as always, please let me know what you think across the board.

Perceptual Effects of Room Reflections, AKA, "It is not Simple!": http://www.madronadigital.com/Library/RoomReflections.html

GaryProtein · Oct 12, 2012

Thank you for that very interesting article.

I will have to read it a second time to get more out of it.

JackD201 · Oct 12, 2012

Hi Amir,

As is your usual request, here's the only typo/editorial error I spotted.

Do We Measuring What We Hear? should read Do We Measure What We Hear or Are We Measuring What We Hear.

Thanks for clearly highlighting that the Haas and Inter-aural delays have workable windows. I've always been a bit dismayed when people say the first reflection should always be killed off. It's poor science yet as you state it has taken on a life of its own in various fora propagated mostly by boiler room acoustic product makers. Great article.

terryj · Oct 12, 2012

JackD201 said:
Hi Amir,

As is your usual request, here's the only typo/editorial error I spotted.

Do We Measuring What We Hear? should read Do We Measure What We Hear or Are We Measuring What We Hear.

Thanks for clearly highlighting that the Haas and Inter-aural delays have workable windows. I've always been a bit dismayed when people say the first reflection should always be killed off. It's poor science yet as you state it has taken on a life of its own in various fora propagated mostly by boiler room acoustic product makers. Great article.

well, if we are after typos (?) in addition to that there is the following

Listening Tests

This is all fine in theory but how does it work in practice? There is good news and bad news. The bad news is that little of will likely make sense to you! The good news is that for a change, distortion will become our friend and not the enemy.

Not much I'll admit, these were the only two I noticed.

enjoyable, thanks amir.

FrantzM · Oct 12, 2012

Hi

First thing that came to my mind is a speaker that bothers me but that many people find great sounding: THe MBL 101.. it ought not to work in my first view of things and it is not my personal cup of tea by the way... But many find it appealing and your article comes a long way in explaining why .... As usual immensely instructive...

microstrip · Oct 12, 2012

Amir,

Great article - thanks for addressing so clearly the differences between the pro and the audiophile community.

Phelonious Ponk · Oct 12, 2012

Good stuff, Amir, and it explains much. Particularly the fact that, even with the obvious bass problems inherent in room gain, a reasonably soft room that is a natural mix of reflective and absorptive surfaces usually sounds better than a heavily treated one. At least it does to me. I'm not even sure it's that much different for pros. Most of the control rooms I've been in are a very deliberate mix of the absorptive and reflective. We all know that anechoic rooms sound unnatural, once we've heard them.

Tim

RBFC · Oct 12, 2012

This article raises the question: Once one is trained to hear various distortions, does this increased ability act as a "curse" which prevents enjoyment of material that carries these (once anonymous) distortions?

Thanks, Amir! A few typos, but very informative!

Lee

microstrip · Oct 12, 2012

RBFC said:
This article raises the question: Once one is trained to hear various distortions, does this increased ability act as a "curse" which prevents enjoyment of material that carries these (once anonymous) distortions?

Thanks, Amir! A few typos, but very informative!

Lee

Lee,

Do I see I am not the only one to deliberately avoid taking the online Listener Training Software course at Sean Olive blog?

Phelonious Ponk · Oct 12, 2012

microstrip said:
Lee,

Do I see I am not the only one to deliberately avoid taking the online Listener Training Software course at Sean Olive blog?

I won't be taking it, micro. We disagree on much; we're in sync (or perhaps we have synergy?

) on this issue. I do not want to train myself to hear artifacts and distortions. Given my uses for music, I see no advantage in it.

Tim

amirm · Oct 12, 2012

Thanks for the corrections guys. Please keep them coming. The ones you pointed out are the ones I edited in the online version trying to make it more readable. So thankfully they were not in the print version.

And thanks for the kind words. When I was first exposed to this in a presentation by Alan Devantier (Harman/Infinity designer), I could not believe what I was hearing. I thought I knew acoustics and then I am sitting there gasping as I am told these things. It just made no sense that a reflection would be better than none. It take a 2-year journey of extensively reviewing the literature, sitting through a ton more presentations, arguing the points with others

, reading Dr. Toole's book over and over again, and digging through 50 to 100 AES and ASA papers that I realized the amazing consistency of it, and lack of disclosure in public. This is a subjective field but to see so much agreeing with the point of view, is quite surprising. And pleasantly so thankfully.

I don't know that I have ever studied a field this extensively and intensively. My hope is that with these articles you get a good summary of it so that you don't have to go through the same effort

. And expense

. Of course, it is no substitute for the experts work and research. With these primers and summaries in hand, it will be easier to read what they have written.

Phelonious Ponk · Oct 12, 2012

amirm said:
Thanks for the corrections guys. Please keep them coming. The ones you pointed out are the ones I edited in the online version trying to make it more readable. So thankfully they were not in the print version.

And thanks for the kind words. When I was first exposed to this in a presentation by Alan Devantier (Harman/Infinity designer), I could not believe what I was hearing. I thought I knew acoustics and then I am sitting there gasping as I am told these things. It just made no sense that a reflection would be better than none. It take a 2-year journey of extensively reviewing the literature, sitting through a ton more presentations, arguing the points with others , reading Dr. Toole's book over and over again, and digging through 50 to 100 AES and ASA papers that I realized the amazing consistency of it, and lack of disclosure in public. This is a subjective field but to see so much agreeing with the point of view, is quite surprising. And pleasantly so thankfully. I don't know that I have ever studied a field this extensively and intensively. My hope is that with these articles you get a good summary of it so that you don't have to go through the same effort . And expense . Of course, it is no substitute for the experts work and research. With these primers and summaries in hand, it will be easier to read what they have written.

Amir, this is one area where I would join the subjectivists and say "trust your ears." Anechoic rooms sound bad, and they start sounding bad before they get to absolutely anechoic. Of course most of us don't get much of a chance to hear them, but there are a couple of reasonable substitutes -- have some stand mount speakers you are very familiar with? Take them outside and play them into an open space. Dry as unbuttered toast. Some in-ear monitors, with very flat FR just don't sound right either. Which is why, if you look at FR charts on headroom, for example, you'll see substantial amounts of "room gain" built into the very best headphones on the market. I love the confirmation all your good work provides, but I'm not surprised by the results. And it's good news for people who don't want to live in domestic spaces that look like studio control rooms.

Tim

RBFC · Oct 12, 2012

Typos

Amir,

I hope this helps:

But peel the layers of the onion and a far more complex picture emerges. And one that is anything but intuitive at times.

Second portion is a sentence fragment, and shouldn't stand alone.

Without that understanding you would easily miscompute the dynamic range by tens of decibels! Not a small error.

Sentence fragment at the end again.

So I thought I would continue the theme by covering more topics related to how we hear sound in a room. Specifically how we perceive sound above the so called “transition frequency.“

Sentence fragment at the end.

Not a pretty sight.

Same.

As we see in the there,

"As we see in the graph there.."

The higher the auditory filter tuning frequency, the lower the resolution of the ear at that frequency.

Sentence fragment, no verb.

These are what I had time to do so far. This editorial view extends up to "Listening Tests". I sincerely hope this helps!

Lee

amirm · Oct 12, 2012

Thanks a bunch Lee. On the fragmented sentences, what is the consensus about that? I know strictly speak it is wrong and I used to obey that religiously. But then I see the style repeatedly in articles to give them less formal feel so I have started to use them. Are folks bothered by their incorrectness or see them as I just mentioned?

Here is a quick example: http://news.cnet.com/8301-1023_3-57...rality-is-incompatible-with-internet-freedom/

"So, no worries? We're all for "Internet freedom" now?

Not so quick."

What say you?

Phelonious Ponk · Oct 12, 2012

I'm personally a fan of the well-placed sentence fragment.

Tim

jkeny · Oct 12, 2012

Yea, right on

microstrip · Oct 12, 2012

Phelonious Ponk said:
I'm personally a fan of the well-placed sentence fragment.

Tim

Tim,

Are you going to change your signature to:

" In high-end audio, you can't even fight an opinion with the facts, you must fight it with sentence fragments" ?

RBFC · Oct 12, 2012

You asked for editorial help, I provided what I know about technical writing. I still got your points.....

Lee

Phelonious Ponk · Oct 12, 2012

microstrip said:
Tim,

Are you going to change your signature to:

" In high-end audio, you can't even fight an opinion with the facts, you must fight it with sentence fragments" ?

The facts can usually be conveyed just fine with fragments. It's the BS that requires long, convoluted compound sentences.

Tim

amirm · Oct 12, 2012

RBFC said:
You asked for editorial help, I provided what I know about technical writing. I still got your points.....

Lee

And I was very appreciative of that

. Please keep them coming. So you know how bad my writing can be, I pay my son to proof read my articles! Even with that I miss some typos

.

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