1st Test Results - no ballast

I just completed my first VERY subjective test of the two tracks without ballast and I can't tell any difference between the sound of the two when running my sound loco both with the sound off and sound on.  It's my understanding that gluing down the ballast (with the cork directly on the 2" foam) will increase the sound level.  That will be my next test.

" It's my understanding that gluing down the ballast "

   It's not a scientific study but I was checking the rolling characteristics of an N scale car I had just changed wheels sets on and I found that rolling it on a piece of loose flextrack just sitting on my plywood benchwork was quieter than rolling it on a piece of flextrack glued down to cork and the plywood.  This seems kinda counter intuitive to me as I would guess that loose flextrack would vibrate more than glued down flextrack and that an N scale car could not move the plywood base enough to make any increased sound from transmission. I have no explanation for the phenomenon ? ....DaveB

Foam drum- use underlayment

There has been a lot of discussion about this on the Yahoo Layout Construction discussion group. The conclusion there was gluing the foam to an underlayment of tempered hardboard like Masonite cuts the foam drumming sound down dramatically. It is important to glue the foam to the hardboard with a foam friendly glue, usually in the large tubes that contractors use. I have used both the DAP 230 Flex and the blue and tan tube product "Liquid Nails" or something like that (senior memory moment). The contrast between that foam and just plain foam over nothing was very clear.

Also I usually lay down a sheet of cork on top or lay track on Homosote (California Roadbed's "Homabed") but those by themselves over the foam will not cut the noise from the foam. It is the underlayment of Masonite which somehow cuts the drumming sound.

Rob Spangler who is an MRH member runs the Yahoo Layout Construction group and probably will have more information on that topic.

John

More Info?

Not really.  Threads on reducing noise in the roadbed structure don't hold much interest for me personally so I mostly let them run their course while only reading enough to ensure people are behaving.

Who needs calibrated ears?

Dear Rick,

Your ears may not be calibrated to a 0.01 of a dB SPL @ 1kHz, but they do have the unique advantages of:
- being part of you (no need to rememember to carry a dB meter),
- being wired directly to your brain (which is where you actually make sense of the airpressure changes your ears consider to be sound)
- and automatically adjusting for various test "listening distances"

SO, if a given option sounds better to you than another, don't apologise for it, it's what your ears say sounds right...

Now, couple of caveats:
- I'd reccomend testing with a non-sound loco, as the thing you're actually trying to "test" is the mechanical "noise floor" over which the "onboard sound system" has to be heard.
(reduce the "noisefloor", and the onboard gear doesn't have to work as hard/loudly to achieve a "pleasing" result)
- Stay off the alcohol before/while performing these tests. Alcohol in your system impairs your sensitivity to high frequencies. In extreme cases, this could mask a higher-frequency harmonic "ringing" in thinner benchwork.

Happy Modelling,
Aim to Improve,
Prof Klyzlr

Dear Dave, Transmission of

Dear Dave,

Transmission of soundwaves thru various materials is all about the contact surface area, contact method, amplitude of the vibration being applied/transmitted, and the frequency we (may not) want to transmit. Your "just placed on a surface" flextrack is minutely bouncing on the underlying plywood, and only really transmitting the noise enough to resonate the plywood at very small moving contact points.

Flextrack glued with a continuous thin layer of glue has a far larger surface area with which to transmit vibration, which both makes it easier (if the amplitude is enough to overcome the increase in mass-to-be-moved and laminated rigidity), and tends to lean towards transmitting lower (more "rumble") frequencies.

Happy Modelling,
Aim to Improve,
Prof Klyzlr

my only measuring device will be my ears

That's the best tool around. One thing I have discovered is there is a very definite threshold between "drumming foam" and "non-drumming foam". Locos with quiet mechanisms may not (should not?) trigger the resonance, but once it kicks in it is unmistakable. Just drag your fingernails along the foam to experience the sound you are looking for.

pqe

Resonant Amplitude VS Material properties

Dear PQ, MRH "Harmonic Rock" fans,

Yep, in order for any material to "resonate" it has to achieve/exceed a certain amplitude (in aural terms, volume).

Below that, the material's own internal structure is able to absorb the energy (presents enough "inertia" or "resistance" to the applied force) and "returns to rest". (The average current-generation "precision loco mech" operation generally does not produce enough amplitude of vibration to push the track and material into obvious/audible "harmonic" behaviour state)

However, exceed the resonant amplitude of the material, and the harmonic vibration within the material will start summing with the existing/applied motion, to the point where they will re-inforce each other, (Sometimes referred to as "Sympathetic Resonance"). 

with (at best) audible annoying rumbling
(or pleasing harmonic tone, think any form of acoustic instrument with a hollow body, like a guitar),

thru to (at worst) actual physical failure (think metal fatigue).

Remember the Tacoma Narrows, the bridge was designed to handle a given amplitude of wind-induced sway, but when the wind "turned it up to 11" at around-the-right-frequency, the induced movement overcame the bridge's  own structural rigidity/resistance/inertia, (which by design we know wasn't really all that high anyway),

and started "sympathetically amplifying" the rocking motion/'vibration".
Catastrophic results followed, once the metal simply exceeded it's design capabilities. 

Happy Modelling,
Aim to Improve,
Prof Klyzlr

PS Physics tells us that all materials have a resonant frequency at which they will react, even if that frequency is outside the range of human hearing. (Think Dog Whistles at the high end, and steel-reinforced concrete structures at the low "Earthquake" end of the frequency spectrum). 

FWIW, the average human body is oft-quoted as being "resonant" at down around the 7Hz mark. (Realistically, if you apply any significant amplitude of vibration below 10Hz to a human, it's likely to make them feel "uneasy" if not downright "unwell"... :-( ).

Calibrated ears

Prof,

I think that might make the solution to this problem real easy. All operation sessions are required to have a three drink minimum.

thats what I thought

That's what I thought but I had no way of articulating it as well as you did nor did I have the scientific background in the field necessary to back it up. Thanks for making it understandable.

Rob in Texas

Colateral damage

Dear Rick,

Might make crew communication a bit difficult, and it might require enlarging the crew lounge to handle all the "gotta sleep it off after the op session, can't drive home right now" bodies...

Happy Modelling,
Aim to Improve,
Prof Klyzlr

On a side note

This will be bordering on the smart posterior type of comment and it is not meant to be so. It is also half in jest but some things have come to mind regarding noise and its transmission. I am also taking pain killers at this time for some back issues. So if this is too far off in left field attribute it to medication and pain.

Background: I have several sound locos and they are loud, they could be louder, they are loud enough that fellow club members ask if I can turn them down. This is not full volume.

What would happen to this unwanted noise if the volume were really cranked up and one installed some cotton in ones ears to reduce it to a volume that was acceptable? I think the unwanted noise would be drowned out by the wanted noise. The unwanted noise does not have a volume control so should be constant what ever level it is.

Installing cotton balls in ones ears has little effect on the cost of the layout and may have the added benefit of wax removal.

Better living through medication. I sure wish it was April 1st.

Rob in Texas

If they are loud enough that others ask you to turn them down ..

... perhaps you should get your hearing checked?  Not joking ... my mother-in-law was always shouting on the telephone and would have the volume of the radio/TV set high enough that it could be heard in adjoining rooms (disturbing other occupants of the house).  Now that she has a hearing aide, things are a lot quieter around here, and it is much easier for her to follow along in conversations.  Of course, sometimes she prefers the 'peace and quiet' and removes it ... heh.

my hearing has been checked

My hearing is fine and has been checked. Real trains were loud as well. I appreciate your concern over my well being. I am just wondering if you noticed the comment about April 1st.

Rob in Texas

Good work, Rick! Thanks for

Bruce - rip up the track with a ripcord!

Bruce,

You're welcome - I'm glad that you found the post helpful, if not entertaining.  As far as removing my test tracks I'm going to use a ripcord - the same once discussed on my thread HERE.  I'll just slip the ripcord under the cork / WS foam and use a sawing motion to separate it from the foam benchtop.

Results are in

Track removal tool

Given the experiments I'm doing (see the foam drum threads) I knew I'd be removing track a lot. So I invested in a tool:

This is an artist's palette knife from my local art supply store. The blade is .02" thick. I ground an edge on it and honed it a bit, and it pops caulked track right up. Cost was $6.

pqe

Pelsea - great idea!

I like the idea of using the palette knife and I believe that I have one around here somewhere.  Thanks!

Tips and tricks

  Looks like a couple of these ideas need to go to the "Tips" guys in MRH ...

Toni

calibrated ears

I send my ears out every 6 months to an NIST-accredited lab for re-calibration.  It's a really great service.  The only down-side is that while they're out for re-cal I can't hear anything......

I have first-hand experience with some of the above construction methods.  I'm in a modular group.  I had a new module with flextrack glued to cork, which was glued to 1/2-inch ply, no ballast yet.  My older modules were flextrack, cork, 2-inch pink foam, glued to 1/4-inch ply, and the track is ballasted.  A friend had another new module with flextrack nailed thru cork, into 1/2-inch ply, no ballast yet. 

The nailed track was very much quieter than any of my modules.  Both types of mine had equal track-noise levels.

I'll fill in more info after I ballast the new module, to see if there's a change.  Also, whenever my friend gets his ballasted, as he intends to pull out the track nails after the ballasting is done.

I would like to try the method of cork put on top of "camper tape" (foam-rubber tape).