Talk but not walk?

prof,

I kind of enjoyed this thread. Probably due to its bizarre turns. There were inexplicable characters, weird responses ("your adult diapers are elastic", or something to that effect), some concise and sharp observations, strange non-questions, a few topics completely unrelated to the original one floating around at random, a little bit of basic physics ("what is sound"), some pointers to other websites, one potentially interesting link on youtube (even if it was me who posted it), and food for my own thoughts rising from all the jungle I just mentioned. It was all quite entertaining. I learned, prompted by the thread but not in it, about some design features of airplanes, paint quality issues, how drums get tuned, botany (Nevada trees), CD-making process, dynamic ranges of albums I have, and a few more things. I have to give Michael Green credit and thanks for that. Had I started a thread, it would have died after a post or two. As this is supposed to be "hobby" website, I consider coming here "waste of time" or "entertainment" so I will have to admit that it served the purpose. All along, while following discussions on audiophile website Audiogon, I sat in silence or, at best, listened to Internet radio on $50 Bluetooth speaker. Not that I did not need room tuning, I probably would not have been considered worthy of logging in. Life is good. Just do not take it too seriously. I am sorry you got so upset.

Turbulent flow occurs at high Reynolds numbers and is dominated by inertial forces, which tend to produce chaotic eddies, vortices and other flow instabilities.

The Reynolds number Re is defined as,

Re = fluid density x fluid velocity x characteristic linear dimension / dynamic viscosity of the fluid

where:

ρ is the density of the fluid (SI units: kg/m3)
u is the velocity of the fluid with respect to the object (m/s)
L is a characteristic linear dimension (m)
μ is the dynamic viscosity of the fluid (Pa·s or N·s/m2 or kg/m·s)
ν is the kinematic viscosity of the fluid (m2/s).

Reynolds number is proportional to the velocity of the fluid (air) which is rather low in a listening room, so Reynolds number will be relatively low. I don’t recall my pants legs flapping in the breeze whilst listening. It’s not exactly a wind tunnel. So turbulent flow is very unlikely or perhaps impossible. This is not to say there might be some advantage sonically to “organizing” laminar flow using shutters. Remember organizing laminar flow doesn’t mean there has to be turbulent flow or that turbulent flow is prevented.

I personally would have to experiment with the shutters to see what happens sonically. The viscosity of the air in a given room will be fairly constant except in the case of bowls of ice cold water, one or two or three or more, that I mentioned, in which case the viscosity and thus the Reynolds number will be different lower in the room than higher up. Reynolds number is mostly a function of temperature. And the speed of sound is slower in cold air than warm air. Therefore the part of the acoustic wave higher up in the room will be faster than lower down so that the wave will bend over and down toward the listener position. He will hear more of the sound, especially the treble, including ambient information. But because of the speed of sound issue not really Reynolds number.

geoffkait,

That is the beginning of what I was thinking about in my hypothetical room, or let’s say that room that you had copied the article about. Although, I was, in my mind, playing with multiple variables of the equation. I was mostly wondering about density and that was, in fact, how I imagined the change in Reynolds number. You picked viscosity. All the same for practical purposes of theoretic imagination. I envisioned different air composition. In my thoughts, I used Helium. I guess 80/20 would be preferred. That led me to thinking what happens to the sound perception (actually, I called it simply "sound") with changes in density of the medium and how it would affect the direction, energy transfer, and whatever else may be involved. Even that unfortunate laminar flow would be greatly affected or enhanced so, if it actually matters, it would affect the sound based on that fact, too. I went through those mind exercises without coming up with any conclusion I would be able to stand behind, but it was a fun exercise for me. Sure, it would be quite complicated to do it in real life, not impossible but prohibitive on more than one level. Making a room Helium-tight would be a decent challenge. For most, just the price of HeliOx would be ridiculous even for a relatively small room (and the one I was imagining was the one on the picture on MG’s website next to where laminar flow is mentioned and it seems quite large). I think that canister is around $700, but may be very wrong about that one. You would likely need many of them. All in all, it was just an exercise, not anything I would consider doing. I was not thinking of change of Reynolds number as means to enhance laminar flow (although that is how I remembered it at first), but as a product of changed density. In my mind, I changed the density which then changed the Reynolds number, and conveniently that would also do something to flow characteristics, in case anyone is interested in that part.


However, it all did come to me from my post you may not recall. In it, I mentioned how I was interested in what methods Michael Green uses to determine where to place his shutters as it seems impossible that placing them in the same position in different rooms would yield same results. You could get it by luck, but then you could also just throw a few pillows around and call it a day, too. That is when I mentioned I find it hard to imagine how it may be done because I would guess it would require equipment and staff for laminar flow measurements and then doing it at different heights and temperatures which I cannot imagine being very convenient even for a well-run business. I may be wrong on that. Temperature was that link from Reynolds number as it, as you pointed out, affects at least viscosity. That is why I actually did stop and think about your ice-cold water for a moment.

Velocities in any kind of listening room are probably very low and likely cannot be greatly influenced, but viscosity and density could, as above. However, there will practically always be some turbulent flow of air in a vessel, in our case the vessel is listening room. If the walls are perfectly smooth, paints differ wildly on that one I just learned, turbulence will increase with distance from the wall, making the middle of our listening room the most vulnerable spot. Of course, add a chair or two and all bets are off. I speculate that, barring a hurricane in the room, turbulent flow will not have much influence on the propagation of sound. I am not saying none, but not much. Of course, for this purpose anything may be important.

That all was just trailing on my initial question about "organizing laminar flow". All of this above had nothing to do with that initial question, but it somehow got out of hand when I thought of it.

The more I think about that "organizing laminar flow", the more I am getting a feeling it is just poor choice of words. Not that I am a firm believer in it for CD-listening purposes, but am focusing on basic statement I read on website.


I am sorry if all of this above is not written clearly, I just wrote as fast as I was thinking about it and as fast I could write it, I did not edit it as it is very late.

For the purpose of this thread, I just talked the talk. If anyone is willing to walk the walk and do what I imagined above, I will humbly admit you are a real walker.

glupson, as a matter of fact Michael and I both talk the talk AND walk the walk. He and I have both been exploring room acoustics for a very long time, independently. He and I have spent extraordinary effort and time finding out how things work. I was one of Michael’s first customers around thirty years ago and have measured the effectiveness of his Echo Tunes and Corner Tunes. Of course many others also were getting their hands dirty and developing products.

I designed and developed quite a number of room acoustics devices that address a wide range of room acoustics problems. My very first product was going to be Ortho Ears for improving dynamic range, modeled after Mr. Spock’s ears, but that product was overcome by events, perhaps fortuitously. Off the top of my head I have at least SEVEN room acoustics products, including some quantum mechanical ones. I developed the first comprehensive crystal-based product line for resonance control and room acoustics control. I have also spent much time and effort studying room acoustics dynamics, including mapping out the sound pressures of the entire 3D space of the room. I have built my own Helmholtz resonators of various sizes, including a 15 foot long folded horn resonator for very low frequencies. I have my own ceramic version of the tiny little 1” bowl acoustic resonators. My hands have not been soaking in Ivory liquid, Junior.

Getting back to the whole laminar flow issue for a second, we know that air moves in the room while music is playing. We also know that acoustic waves themselves travel through air at the speed of sound. These high speed acoustic waves striking a surface would be like waves of water striking the beach, no? So the dynamics of the acoustic wave + air hitting a surface would obviously have a much greater impact than one might imagine. That’s why I measure sound pressure peaks in some locations around the room that are 10 times higher than the average sound pressure in the room. That’s a lot of energy, no?

I do believe the whole subject of room issues is very real and goes way beyond what  alot of people work at with bass traps and wall diffusers etc.
After all you only need look at some websites to see what some are selling just as off the shelf items,
And I do believe certain people spending years in the research and counterpoint of these effects has been productive.
I wonder though with the wave of the latest electronic correction devices if this has somewhat negated all of this effort?

I wonder just what effect a unit like the Lyngdorf 2170 or Anthem would have on the rooms that already been heavily massaged and tweaked?
Would they be able to improve still further?
Or would they possibly make matters worse?
Be interesting to note the amount of room correction they attempt to make.

Personally I have known my room was acoustically terrible for years but then came along the 2170 and as far as I am concerned it did the "walk" for me and in all honesty I am just about done and really just sit down and enjoy the music for hours on end.
Maybe ignorant bliss and contentment but its my room...lol.