Giant Toilet Paper Tubes

Post and discuss acoustic topics, Studio design, construction, and soundproofing here

Giant Toilet Paper Tubes

Postby Bob » Fri Aug 13, 2004 5:02 pm

http://web.archive.org/web/200108030528 ... mTubes.asp

Chapter 1 has some beautiful room mode GIFs.
Chapter 2 talks about the usual trapping
Chapter 3 is where it starts to be a new construction method.
Regards
Bob Golds
"The only thing we regret in life is the love we failed to give."
"Be a rapturist -- the backward of a terrorist. Commit random acts of senseless kindness, whenever possible" - Jake Stonebender
Bob
 
Posts: 4358
Joined: Sun Feb 08, 2004 4:37 am
Location: Oakville, Ontario, Canada

Postby Scott R. Foster » Fri Aug 13, 2004 7:35 pm

Bob!

Neat site, great animations, clever fellows... but as I read to the conclusion of their story, I find the results are supportive of the objections myself and others here have long pointed to with regard to the narrow band approach to resonance control [Helmholtz bottles, pipe traps, membrane absorbers, etcetera]. That being, that in a narrow band approach you have are tuning and tweaking a set of absorption wells in an attempt to achieve balance against an extraordinarily complicated vibration field... the sensitivity to initial conditions, and iterative nature of that field is a ripe field for results that are kinda sorta almost right... better over here, but worse over here... we've got the 73 Hz hum tamed, but now the 111 Hz drone seems worse.

To be fair, the author does explain some of the complexities... but he then goes on to ignore em because physics simply does not allow a mere mortal with a stack of cardboard tubes and a couple of "rule of thumb" acoustic formulae to address phyical realities like oblique modes and non perpendicular angles of incidence.

Also, there are what the site's author calls "artifacts". The left overs from the treatment process that re-emit into the room cause groan and rumble.

I know some the smartest folks in this forum [and that is amrt indeed] have used narrow band devices effectively - I aint saying they can't be effective - I restrain myself to comment for the benefit of new comers to our field of discussion who are looking for the "magic bullet"... and say to such folks, there aint no magic bullets but there are many paths to Buddha, and some are low cost and uncomplicated.

For a quick down and dirty fix to an elusive problem, I guess I can see resorting to the sonotube approach, and indeed this idea [cardboard concrete column form] is a clever / cheap way to go... especially when one is able to focus on results for a single listening position. For example this sort of thing might be a great quick, cheap portable solution for a guy trying to tame the worst of the resonances in the spare bedroom of his apartment where he wants to mix up some demo tapes for his garage band. I reckon noticeable improvement would be achieved - quick and cheap - and that's a very good thing.

BUT, for a similar cost and effort, and a lot less calculation [where a noobie could easily get lost - I have been fiddling around with this stuff for years now and I always get my first set of calcs wrong somehow], one could use a broadband approach such as SCA's and get something equally portable and there would be a lot less risk of endlessly tuning the thing to try and get results... in fact I'd reckon SCA would work better first try - I am even more willing to predict superior results if our hero will add a couple of polys to back walls to provide some diffusion to work in conjunction with the absorption of SCA's.

For a home theater guy I'd guess that either a SCA or SSC and a few polys would be a much better way to go as the listening positions are spread around the room and small imbalances in the tuned absorber array and their artifacts are likely to cause noticeable problems to some users / positions no matter how you arrange the pieces.

OTOH if $ are exchanged for time, effort, calculation, one could simply purchase some ML's and some form of back wall diffusion and probably solve the problem as good or better than either of the above approaches by any measure.

My $0.02

*edited for clarity ["tube" replaced with "pipe"] thnx Z]
Last edited by Scott R. Foster on Sat Aug 14, 2004 12:43 pm, edited 1 time in total.
SRF
Scott R. Foster
 
Posts: 3854
Joined: Mon Feb 02, 2004 12:41 pm
Location: Jacksonville, FL USA

Postby Ido » Fri Aug 13, 2004 7:40 pm

Scott R. Foster wrote:Bob!

Neat site, great animations, clever fellows... but as I read to the conclusion of their story, I find the results are supportive of the objections myself and others here have long pointed to with regard to the narrow band approach to resonance control [Helmholtz bottles, tube traps, membrane absorbers, etcetera]. That being, that in a narrow band approach you have are tuning and tweaking a set of absorption wells in an attempt to achieve balance against an extraordinarily complicated vibration field... the sensitivity to initial conditions, and iterative nature of that field is a ripe field for results that are kinda sorta almost right... better over here, but worse over here... we've got the 73 Hz hum tamed, but now the 111 Hz drone seems worse.

To be fair, the author does explain some of the complexities... but he then goes on to ignore em because physics simply does not allow a mere mortal with a stack of cardboard tubes and a couple of "rule of thumb" acoustic formulae to address phyical realities like oblique modes and non perpendicular angles of incidence.

Also, there are what the site's author calls "artifacts". The left overs from the treatment process that re-emit into the room cause groan and rumble.

I know some the smartest folks in this forum [and that is amrt indeed] have used narrow band devices effectively - I aint saying they can't be effective - I restrain myself to comment for the benefit of new comers to our field of discussion who are looking for the "magic bullet"... and say to such folks, there aint no magic bullets but there are many paths to Buddha, and some are low cost and uncomplicated.

For a quick down and dirty fix to an elusive problem, I guess I can see resorting to the sonotube approach, and indeed this idea [cardboard concrete column form] is a clever / cheap way to go... especially when one is able to focus on results for a single listening position. For example this sort of thing might be a great quick, cheap portable solution for a guy trying to tame the worst of the resonances in the spare bedroom of his apartment where he wants to mix up some demo tapes for his garage band. I reckon noticeable improvement would be achieved - quick and cheap - and that's a very good thing.

BUT, for a similar cost and effort, and a lot less calculation [where a noobie could easily get lost - I have been fiddling around with this stuff for years now and I always get my first set of calcs wrong somehow], one could use a broadband approach such as SCA's and get something equally portable and there would be a lot less risk of endlessly tuning the thing to try and get results... in fact I'd reckon SCA would work better first try - I am even more willing to predict superior results if our hero will add a couple of polys to back walls to provide some diffusion to work in conjunction with the absorption of SCA's.

For a home theater guy I'd guess that either a SCA or SSC and a few polys would be a much better way to go as the listening positions are spread around the room and small imbalances in the tuned absorber array and their artifacts are likely to cause noticeable problems to some users / positions no matter how you arrange the pieces.

OTOH if $ are exchanged for time, effort, calculation, one could simply purchase some ML's and some form of back wall diffusion and probably solve the problem as good or better than either of the above approaches by any measure.

My $0.02


OK, but what about the mushrooms?
Ido
 
Posts: 2201
Joined: Mon Feb 09, 2004 7:47 pm
Location: Israel

Postby Bob » Fri Aug 13, 2004 8:38 pm

Scott:

I thought/guessed you'd say something like this: "Use SSC's or MegaLENRDs (ML) first, and then fill the back wall and the near-back sides with these tuned cylindricals (cause I love polys!) to take just a little more edge off the measured modes discovered by ETF5! But by themselves they won't absorb enough of the modes, unless you had the room 80% full of them." :)

(I missed the 'artifacts'. I'll go back and have another read)
Regards
Bob Golds
"The only thing we regret in life is the love we failed to give."
"Be a rapturist -- the backward of a terrorist. Commit random acts of senseless kindness, whenever possible" - Jake Stonebender
Bob
 
Posts: 4358
Joined: Sun Feb 08, 2004 4:37 am
Location: Oakville, Ontario, Canada

Postby Scott R. Foster » Fri Aug 13, 2004 10:48 pm

He did find that the three tubes that end up at the side of the room tend to want to interact with each other and that a bit of fidgeting with position has been needed to reduce acoustic artifact from these tubes.

Our experience in the HeadRoom listening room is that as you carefully move the tubes around, you can hear a faint growly sound when the tubes interact....


On this page

http://web.archive.org/web/200108091931 ... erFive.asp
SRF
Scott R. Foster
 
Posts: 3854
Joined: Mon Feb 02, 2004 12:41 pm
Location: Jacksonville, FL USA

Postby Andrew Steel » Fri Aug 13, 2004 10:53 pm

Interesting site and discussion. What I would like to know is how to quantify any of these things? For toilet tubes and helmholtzs and membranes how many Sabins do they equate to? Does anyone know the relationship?

Andrew
Andrew Steel
 
Posts: 139
Joined: Sun Feb 08, 2004 9:38 pm
Location: Brisbane Australia

Postby Scott R. Foster » Fri Aug 13, 2004 11:12 pm

Interesting site and discussion. What I would like to know is how to quantify any of these things? For toilet tubes and helmholtzs and membranes how many Sabins do they equate to? Does anyone know the relationship?


Andrew:

I think the key is established in the famous "4 devices" thread which in my mind resolves to a question of Sabins per $. In the case of all types of narrow band devices it is important to note that for vast stretches of the band the Sabin count is next to nothing without regard to $ expended.

*edited to lower incoherence
Last edited by Scott R. Foster on Sat Aug 14, 2004 12:39 pm, edited 1 time in total.
SRF
Scott R. Foster
 
Posts: 3854
Joined: Mon Feb 02, 2004 12:41 pm
Location: Jacksonville, FL USA

Postby Zaphod » Sat Aug 14, 2004 8:33 am

Scott R. Foster wrote:Bob!
I find the results are supportive of the objections myself and others here have long pointed to with regard to the narrow band approach to resonance control [Helmholtz bottles, tube traps, membrane absorbers, etcetera].


Scott:

When you say tube traps, you mean the "giant toilet paper tubes"
or something like this: http://www.teresaudio.com/haven/traps/traps.html ?

Since i'm building some myself (only using a lot more rockwool for
the inside layer), i'm really worried of your statment of tube traps being
narrow band absorbers.

Here's a pic of my first prototype (still unclothed) :mrgreen:
Attachments
Da Lontano.jpg
As you see, a lot of furniture here :)
Da Lontano.jpg (63.31 KiB) Viewed 34002 times
Zaphod
 
Posts: 1931
Joined: Wed Jul 28, 2004 9:51 pm
Location: Rome, Italy

Postby Brian Dayton » Sat Aug 14, 2004 9:26 am

those really are some great animations. people are so pictorial in thinking/understanding, sometimes a picture really is worth a thousand words.
Content posted by me is copyright 2004, 2005, 2006  Brian Ravnaas, but may be reproduced without permission for any non-commercial purpose so long as the intent is preserved.  NRC Canada data is copyright them and used with permission, www.nrc.ca
Brian Dayton
 
Posts: 1301
Joined: Fri Jul 02, 2004 5:29 am
Location: fargo, ND

Postby Eric.Desart » Sat Aug 14, 2004 9:28 am

Hello Zaphod,

Nice work.

The tubes described in the beginning of this thread are 1/4 wave resonators executed as narrow band silencers.

Your's are broadband absorption devices, working on a different principle.
So this is not related.

To Scott:
I find those diameters rather small for broadband diffusion.
Very superficial of me: This also relates to the previous thing about those half circles and slightly bend polys.

This is wavelength related. If a frequency reaches an object (see this for the sake of argument as a plain front) where
1) the size of the wavelength is much smaller than the diffuser width it acts as ping pong balls reflecting.
2) the size of the wavelength equals the diffuser width the wave gets scattered (reflected in random direction). This even happens with flat slats. That's why a John sayers slat type Helmholtz absorption approach will also act as diffuser in those higher frequencies.
3) the size of the wavelength is much larger than the width of the object, the wave will not notice the object.

Therefore in most cases the slighter bended panels (are that what you call polys?) will go lower in frequency because the diffusing width is larger when made from the same basic material.

I've seen Bob's link.
That's a clever guy knowing what modes are, and nice explained.
However I'm still struggling with a likely reasoning error for defining the length of the tubes for the tangential modes.
His reasoning seems based on the wrong assumption that 50% of the diagonal is 1/4 wavelength of the related mode frequency.
Must read this again to check if I don't misinterpret anything. Anyhow something doesn't feel right here.

I MUST BE VERY CAREFUL HOW I FORMULATE SENTENCES.
ETHAN READS ANY OF THEM.
EVEN PART OF WHATEVER SENTENCE, OUT OF CONTEXT OR NOT, UNDERSTANDING WHAT IS SAID OR NOT, HE COLLECTS IN HIS SO-CALLED "ERIC's STUPIDITIES" DATABASE.
It becomes his traditional approach to prove how clever he is, as substitute for ....., everytime when he's out of arguments. Simultaniouly he claims that he's the only guy who stays on topic. (Exhausting guy, he probably even believes himself )
Last edited by Eric.Desart on Sat Aug 14, 2004 5:04 pm, edited 2 times in total.
Image
divinely-inspired
Eric.Desart
Moderator
 
Posts: 2461
Joined: Tue Feb 10, 2004 4:29 am
Location: Antwerp, Belgium

Postby Zaphod » Sat Aug 14, 2004 10:27 am

Eric.Desart wrote:Hello Zaphod,

Your's are broadband absorption devices, working on a different principle.
So this is not related.


Glad to hear that.

I assume scott called "tube traps" these tuned wave resonators.
(well they are traps, they are tubes, what else would you expect? :mrgreen:)
Zaphod
 
Posts: 1931
Joined: Wed Jul 28, 2004 9:51 pm
Location: Rome, Italy

Postby Eric.Desart » Sat Aug 14, 2004 11:39 am

:lol: :lol:
Image
divinely-inspired
Eric.Desart
Moderator
 
Posts: 2461
Joined: Tue Feb 10, 2004 4:29 am
Location: Antwerp, Belgium

Postby Scott R. Foster » Sat Aug 14, 2004 12:51 pm

(well they are traps, they are tubes, what else would you expect? )


Yeah!

At least I'm not stupid like that Eric Desart guy.

:roll:

PS: changed it to pipe traps.. how's that... will the judge take that?
SRF
Scott R. Foster
 
Posts: 3854
Joined: Mon Feb 02, 2004 12:41 pm
Location: Jacksonville, FL USA

Postby bert stoltenborg » Sat Aug 14, 2004 12:58 pm

I MUST BE VERY CAREFUL HOW I FORMULATE SENTENCES.
ETHAN READS ANY OF THEM.

Hey Eric,

You can use my name and shout some BS (Bert Stoltenborg) around and nobody will be surprised. :mrgreen:

bert
bert stoltenborg
 
Posts: 4555
Joined: Sun Apr 18, 2004 11:03 am
Location: Achterhood, Netherlands

Postby Zaphod » Sat Aug 14, 2004 1:24 pm

Scott R. Foster wrote:PS: changed it to pipe traps.. how's that... will the judge take that?


Great scott. 8)

I'd say now this thread is Dummies-compliant (myself included :mrgreen:)
Zaphod
 
Posts: 1931
Joined: Wed Jul 28, 2004 9:51 pm
Location: Rome, Italy

Postby Scott R. Foster » Sat Aug 14, 2004 1:53 pm

1) the size of the wavelength is much smaller than the diffuser width it acts as ping pong balls reflecting.
2) the size of the wavelength equals the diffuser width the wave gets scattered (reflected in random direction). This even happens with flat slats. That's why a John sayers slat type Helmholtz absorption approach will also act as diffuser in those higher frequencies.
3) the size of the wavelength is much larger than the width of the object, the wave will not notice the object.


Well if it isn't that dummy Eric Desart come around to have me explain basic acoustics to him again.

SIGH

:wink:

Ya, that makes sense to me - the tubes are what, 12" in diameter? So that's a full wave size for 1130 Hz? I would reckon the collective diffusive effect of a room full of these pipe traps is worthy of mention, but it would be easy to over state. I reckon 6 of these at 6 feet tall and 1' wide are equal to what... a single 4'x8' poly on the wall? Or, does the free standing installation [versus flat to wall] give an all aspect effectiveness [both front and backsides are at work] to make em more like a pair of 4x8 polys?

And of course that ratio [whatever it is] is effective only above the minimum frequency... whatever it is for a 12" tube, a 4x8 poly is gonna be much lower, so for frequencies below the pipe's limit the ratio is infinite.

Also, there is the supposition we previously discussed of a perfectly circular aspect have reduced diffusive qualities versus a flatter polyclindrical shape as you allude to above. FWIW I would be inclined to guess it'd wouldn't be much different than a 6 = 1 ratio [six 6' tall tubes gives about the same diffusion as one 4x8 poly], but that is an absolute WAG... real data would be a fascinating read [hint hint... anyone?].

Hmmm

And, how much wave must a gross diffuser catch to have an appreciable effect?*

* by "gross", I am trying to label that class of diffusive elements that work because of overall shape as opposed to some smaller surface convolutions / feature such as bumps, grooves, wells or slats

This is a question that has irked me re polys for sometime... does it take an 11.3' poly to work down to 100 Hz - or is it half wave [5.65'], or even the dreaded 1/4 wave at around 3'??? Anyone run across a clue in their reading?

Extra credit homework**:

** previous homework for this weekend was a joke - them shrooms have worms in em and are hard on your liver... don't do drugs - stay in school - I'm talking to you Mr. Dayton!]

A 4'x8' poly bent along its long axis is an effective diffusive element down to __ Hz?***

What if it is bent along its 4' axis?

***to simplify, ignore 2d aspect surface area losses caused by the bend - assume the size is 4x8 after the bend is made.

Extra Extra credit homework:

How many of these

http://cgi.ebay.com/ws/eBayISAPI.dll?Vi ... 3831337980

do I need to make a portable keg cooler... assume you can get a broken refrigerator box from the junk yard and use it in your design / answer if you want... like this one

http://www.sportys.com/acb/showdetl.cfm ... uct_id=984

WARNING! this guy has a head start on you, AND he has funding!

http://www.case.edu/news/2004/4-04/keg.htm

PS: best solution will use an even number of devices so I can series [series / parallel] the the loads to match the 24v outlet on the back of my Pinzgauer [located just to the right of the LED tail light].

Image
SRF
Scott R. Foster
 
Posts: 3854
Joined: Mon Feb 02, 2004 12:41 pm
Location: Jacksonville, FL USA

Postby Eric.Desart » Sat Aug 14, 2004 2:41 pm

Scott,

I haven't checked your links yet.
Exact scattering/diffraction is complicated. It's a typical weak point in simulation models.

So just practical:

A reverberation room of (advised in both ASTM and ISO) 200 m3 = 7063 cft (minimum in ISO = 150 m3 = 5297 cft, in ASTM = 125 m3 = 4414 cft ) is designed for a cut-off of 100 Hz.

ISO recommends diffusers (those bend panels, NOT 1/2 circles) of 0.8 (8.6 sft) to 3 m2 (32.3 sft), they don't define a lenght/width ratio, with a weight of at least 5 kg/m2. (1.024 lb/sft)
They describe: the sheets may be slightly curved but without defining a radius.
Those biggest diffusers are often a standard commercial panel sizes here of 1.22 m x 2.44 m (4' x 8') or 1.2 m x 2.4/2.5 m.
AFAIK, in practice lots are close to the maximum size (since they also diffuse higher frequencies, but smaller are used too for additional corrections). They are meant to assure good diffusion in the room down to 100 Hz (but they are often/sometimes also bended diagonally or anything in between).
As such these diffusers use a combined effect (most are free-hanging):
1) Scattering caused by the relation size versus wavelength (=diffraction).
2) Diffusion caused by the bended shape (effect on higher frequencies).

They will have effect lower too, but that's all gradual and difficult to calculate.
Diffusers in a reverb room are added and mounted or adjusted emphirically (tuning the room to show maximum absorption of a typical absorption sample), not calculated or simulated (one could do that but that's more then to check the simulation model with real live results).

I have more about this but it's time consuming, complicated, which is why I didn't respond previously. I'm plagued with good intends, but this aren't easy questions.

EDITED:
1) With the 100 Hz I meant the lower Cutoff of the 100 Hz 1/3 octave band equaling 89.13 Hz (rounded */- 90 Hz).
2) I completed the conversions now (saving your energy a bit :wink: )
3) Aug 15: adjusted and extended text somewhat
Last edited by Eric.Desart on Sun Aug 15, 2004 8:59 am, edited 14 times in total.
Image
divinely-inspired
Eric.Desart
Moderator
 
Posts: 2461
Joined: Tue Feb 10, 2004 4:29 am
Location: Antwerp, Belgium

Postby Ido » Sat Aug 14, 2004 9:21 pm

[quote="
Image[/quote]

We have a converter, goes into cig sockett, comes out 240 V. you probably know those.
How about a Pinz update? it's been a while. How'd it take summer heat?
did you give it a bigger airblower or something? no need?
did you find it a girlfriend? (mate > little Pinz's).
There is a Japanese artist, who's art is, um, screwing cars (if you must know, in the exhaust tail pipe. where else?).
Nice guy, gave us a lecture at art academy. I love cars and all, and I was thinking like maybe there was something deep, so I ask him why did he choose that specific car (there were pics), and he said: "it was cute".
Ido
Ido
 
Posts: 2201
Joined: Mon Feb 09, 2004 7:47 pm
Location: Israel

Postby Scott R. Foster » Sat Aug 14, 2004 10:07 pm

Apologies for the OT crap - skip the following if you're not interested in non-acoustic home school physics

Ido!

As you may recall we installed a 5kw A genset in the PInz last year and run a 13.5 btu rooftop AC - since we added some thermal insualtion to the roof this works fine.

The reason for the interest in the low voltage cooling solution is that the Peltier chiilers are CHEAP, small in size, efficent, vibration resistant, and easily adaptable to any existing insulated box - project one will be the simple conversion of a standard ice loaded drink cooler so we no longer need to buy ice and we make our drinks cold all weekend without returning to the hard roads and "real" life.

Later, once we we have a base camp with a pond and a pole barn built [way out in the woods] I'll add some high voltage devices to run off the pinz gen when we are out there [well pump for a fountain, fans, a few work lights, outdoor theater, etcetera], but the interest in some low voltage stuff will always exist for stuff we might want to leave running [off a solar panel] when we ar out driving around in the woods... like a keg cooler [massive quantities of coldbeer awaiting our return from the mudholes].

All this stuff is just goofing around... little science projects for me and my kids... but Im having troubling with some of the thermal physics soooo - back method "A", the WAG and see what works.
SRF
Scott R. Foster
 
Posts: 3854
Joined: Mon Feb 02, 2004 12:41 pm
Location: Jacksonville, FL USA

Postby bert stoltenborg » Sun Aug 15, 2004 3:33 pm

Scott,

"Also, there is the supposition we previously discussed of a perfectly circular aspect have reduced diffusive qualities versus a flatter polyclindrical shape as you allude to above. FWIW I would be inclined to guess it'd wouldn't be much different than a 6 = 1 ratio [six 6' tall tubes gives about the same diffusion as one 4x8 poly], but that is an absolute WAG... real data would be a fascinating read [hint hint... anyone?]."

You may shoot me, but I still am not shure what a "poly" is exactly. Is it a panel bent in two perpendicular directions?
And if you want to do measurements on 'm, you would IMHO have to scale them down or you would have the problem that for low freqs you would have to have a very large room to be able to measure them in the free field (= at least 7 wavelengts away). I don't know if a scaled model gives a valid impression. It may sound strange from a bloody Dutchman, but maybe that our friend from Belgium has an idea? :mrgreen:

regards,

Bert
bert stoltenborg
 
Posts: 4555
Joined: Sun Apr 18, 2004 11:03 am
Location: Achterhood, Netherlands

Next

Return to Discussion

Who is online

Users browsing this forum: Bing [Bot] and 4 guests