Randy,
I happened to run across,something else, ''While you were Missing,in PA''. I didn't know that!
Cheers,
Frank
Hi Randy,
You probably already know all of this stuff, but others might not and might find this info. helpful or at least something to mull over.
The underside of the bench top may be the most critical area for sound production reduction.
I once used a decibel meter to see which of my friend's layouts areas (some ply with cork, some foam with cork). The foam bench top area was louder, every time/everywhere. This surprised me as I've always read the opposite. I tried the same experiment on another layout with mixed sections and got the same results.
On both foam tops and ply tops, the track was caulked down not nailed. The nailed down track didn't see to make any appreciable difference but the glue of course is the main hard material as the nails are often pulled anyway. Neither of these layouts used vinyl or foam roadbed.
The decibel levels were higher under the bench tops than on top as that area is more "contained". These were layouts that had things stored under them so that stored stuff introduces a lot of variables. (Acting as baffles, wanna-be bass porting (a bit of a stretch), etc. etc.
The differences between top noise and bottom noise was very noticeable when we tried it after clearing out under the layout. Both of these layout room floors were hard, sound reflective surfaces so it made differences both aurally and with a meter pretty obvious.
Carpet changes the whole picture and is a very good idea at least under the benchwork even if you want linoleum or wood floor aisles, etc.
Radio shack sells cheap decibel meters if you want to explore that tool and don't already own one. It certainly would give more scientific results with some controls built in than by just listening which according to "psycho-acoustics" (another science and another class) is subjective and varies from room to room and the surfaces in the room. Maybe there's a phone app for that...
Once material combination might sound quieter in one room and much louder in another.
This is because room corners are "bass traps". Bass frequencies are non-directional and swirl around near the floor.
Higher frequencies are much more directional. Long rectangular rooms vs. square rooms (horrible acoustics) vary a lot. Various ceiling heights, open vs. enclosed, cathedral vs. standard flat overhead, etc.
This is why down firing dcc sound speakers usually (but not always) give better and more focused bass response. It's also why, when my wife calls me from two rooms away and she never can hear my normally baritone response, I answer her in a high pitched/higher frequency voice and she can hear me clearly.
I did some experimenting with one as described below:
I've taken some sound and acoustics coursework and have been a recording producer and most of the objectionable sound on our layouts (drumming, etc.) comes from the underside of the materials/bench tops. Acoustically, the vibrating table top is known as "drumming".
Model railroader did an experiment years ago where they found the same thing. I can't remember but I think they put some homasote or similar material on the underside of the table top and got the quietest results. It was an article that got a lot of attention for a short time. Sorry I have no idea of issue # or year...at the time is was kind of a "revolutionary" idea and received much discussion but seems to have been forgotten about.
Of course for optimum sound proofing you'd need to have a soft material between the support girders or benchwork grids and the table top but that's going a bit far. Anyway, it might be worthwhile to try tacking some absorbent material under the bench top and see if it's much quieter than only using quiet roadbed materials.
Of course I have enough junk stored under the layout to soak up some drumming sound but everytime we move our junk out of there or rearrange it, the acoustic picture changes.
I'll be very interested to see what your results are and how you go about your trials/experimentation.
I often rely on you for dcc electrical troubleshooting (I'm still in pre-school electrically) so thought maybe I could pay it back/forward a bit.
I borrowed the decibel meter and didn't write down the results, just informal comparisons at the time so can't give hard data at this point, from 5 yrs. ago.
I would think that using wood ties would help some even with caulk. Let us know what you find?
Might be another MR article in it !
Jim
Raised on the Erie Lackawanna Mainline- Supt. of the Black River Transfer & Terminal R.R.
Wow! You guys are to be commended for the depth of thought that goes into so many of your posts!
Randy had a good idea to get some objective data on the sound issue and that triggered more of you to expand on the subject! I for one, prefer quieter train operations, and keep my sound locos at low volume. So track noise is important to me.
I don't post often, but I know that when I start reading these forums it is always interesting!
Thanks fellows! -Bill
I forgot to say, above, that gluing/caulking the foam top down on a piece of plywood would eliminate a lot of the high frequency drumming right away.
Someone on an earlier page asked about acoustic caulking. I used it in my studio walls to isolate the sheetrock (2 layers) from the studs which were staggered to also reduce vibration/drumming, etc.
The acoustic foam is not as cheap as laytex adhesive caulks and I think the difference would be negligible in the benchwork applications-unless you have a cheap source!
That's it. All that being said, I have to admit to desiring some layout noise to simulate the vibrations/shaking of the ground of the prototypes. So I don't go for the really really quiet/sllent wheel noise thang that some folks do.
JIm
Depends on how thick a piece of plywood, I think. My previous layotu just had the foam glued right to the 1x4 framing. It wasn;t very loud. My current layout I put a layer of 1/4" plywood underneatht he foam, between the frame and the foam. It's much louder than the other one was.
A lot also has to do with the wheels I use pretty mch all Proto 2000 metal wheels, except in those cars that come with metal wheels already, or a few oddballs here and there where the exle length is not correct. Even on the current layout, the noise is more of a ssssssssssssssss of the wheels rolling over the track than any sort of rumble or drumming noise. On the club layout, my train is always louder than most everyone elses - most people use Intermountain wheelsets. I may have to switch, through one of our sponsors I can get 100 packs of IM wheelsets for pretty cheap - less than P2K these days, but back when I started repalcing all the wheels, Klein's had P2K wheels for less than any others - that was before Walthers bought LifeLike and ended Klein's sweetheart deal. Plus IM wheelsest are easier to put resistors on.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
Yes, the ply or foam placed directly atop joists, grid frames, etc. will produce and amplify acoustic drumming by-a lot.
An example: Our old motorsailer's previous owner had installed expensive leaded foam sound reduction panels in the lift/hatch boards over the engine room. Unfortunately, he had their frames (wood) placed directly on the support lips (wood) and he completely (well mostly) wasted his money and time on the leaded foam. The DB meter read 100 db! We had to wear ear protection when motoring if we wanted to keep our hearing over (a relatively short) period of time.
If soft/sound absorbent material is used it needs to be between every mating surface to be effective.
Look into acoustic caulking. In your application it's added cost would be negligible. I do not recall how adhesive it is (if you could ever dismantle anything after it's use) so you'll have to read up or ask a supplier.
I would think that at least a (removable later) laytex caulk would help quite a bit to reduce drumming. The center of the foam/ply will still "drum" if not supported closely together by framing members.
If you can get a copy through your library or used book store I highly recommend: "How to Build a Small Budget Recording Studio from Scratch with 12 Tested Designs" by F. Alton Everest and Mike Shea. TAB Books, Pub. My 10 yrs. old copy was $22.
I told my studio friends about this model railroading discussion and one of them has a 2nd copy that he'd sell or trade for some 1930s-1940s rolling stock, etc. I looked on Amazon dot com but didn't see it listed there.
At any rate, it covers in layman's language (and enough technical stuff to keep technical guys happy) all of the things plus a lot more, that I've discussed above.
Hope all this isn't too much, but it's really not a simple problem/solution without taking the room, the mating of materials, the moving sound in the room, etc. into consideration IF one is seeking perfection to their ears. I have to say, that in this age of (horrible!!!) mp3 sound recordings, etc. it's rare to find people who value sound and acoustics and can even hear the difference.
Cheers and hope this helps and isn't way overboard for the thread,