Why is my trestle so quiet?

[selector]

I have only been using this forum for about two months, so if this is a well worn topic, please cut me some slack.

I used available EZ Track for my layout, and then ballasted it with cleaned beach sand. It worked well, especially since I overcame my lifelong impatience with detail and arranged it all carefully.

Later, when I ran the trains, there was, as you might expect, a fair bit of running noise over the ballasted track (it's on a foam base). But, when the loco and train passed across the trestle, it was like I had suddnely gone deaf! I'm not kidding.

Can someone with a semi-academic approach to this puzzle help me to understand why?

BTW, if anyone 'new' to railroading is reading this, I now realize that using 1" extruded foam as the base for my main line did little to dampen the anticipated running noise, and I fear that my choice of EZ Track may have been the major contributor to the problem. Perhaps the plastic ballast base amplifies sound?

For those who lay their own track, how have you overcome noise? It seems having a QSI - equipped steamer is almost counterproductive if it competes with rail noise of the type that I have. [V]

[Anonymous]

I prefer cork roadbed and spikes on track. The trestle does not provide a "sounding board" like one used in a guitar. There is no reflective surface for the sound to bounce back off below the engine.

I am willing to bet the plastic track probably "tunnels" the sound everywhere but the trestle.

[Anonymous]

I'm probably the only one on the planet that has never even seen EZ Track. (No LHS up in these hills.)

Is the base concave when looking at the bottom? If so, perhaps like a musical instrument, the air in it is vibrating and the tabletop below is acting like a soundboard to amplify the sound.

The sound board is not there on your trestle.

Wayne

[selector]

Thanks, fellas. So would you rate the cork as "highly effective at dampening track noise", "fairly effective", or "barely effective" if the noise coming from track tastened directly to plywood were an 8/10, and the awesome quiet of a train on a trestle were rated 2/10?

Thanks for your responses, in advance. I will not use EZ Track again.

Muddy, EZ Track is a godsend for those who can't, or won't take the time to hand lay track. Most commonly nowadays, it is silvery nickel steel over shallow black plastic ties secured to an all-grey plastic ballast. It comes in 9" lengths for straight pieces, and the various radii of curves have different lengths. The pieces are held together with thin metal tabs called rail joiners that generally do a good job of providing electrical connectivity and aligning the rail ends. As you would expect, the plastic ballast raises the track about 1/2" off the surface, and is hollow. I am sure that it has nasty acoustic properties, but the Flex-Track on the trestles is ultra-quiet.

[Javern]

i have noticed that noise increases a lot after glueing and ballasting, nice and quiet until then. Once the roadbed, track, ballast, etc all become a bonded one then it's a noise machine

[RoyalOaker]

Selector

This is just a thought and I don't know if it will work but.....

There is this stuff called "Great Stuff" that is an expandable foam used for sealing cracks between windows. It is designed to not push on the surfaces it is sprayed against. You can buy it in a spray can size from any home repair store.

Perhaps if you squirted a small amount under every "EZ track" piece it would act like a baffle and no longer tunnel sound.


Again, I am not sure how this could be done, just that I think it might work.


Good luck

[RedLeader]

Man this is weird! In my case it happens the opposite. I use cork as roadbed over playwood. The thing is soundless and I can even hear the squeechy noise of some old wheels. When the train passes through my trestle, the I can hear a noise amplification. The reason: Ahh... plain physics. The cork absorb the noise, just like foam would, preventing sound waves to reflect and/or amplify. In the case of the trestle, the track is directly placed over the beems and the piles that rest directly over the playwood. Sound travels through the very rigid structure down to the playwood and the cavity formed below my layout works as a soundboard, just like a drum.

[selector]

All interesting, and helpful, replies. Thank-you, Gentlemen.

I think I will try both techniques on a small strip of plywood and see which is the quiestest.

RedLeader, I fudged my trestle so that it only has slightly splayed bents in pairs. I don't use the four or more verticle pilings, but only two, with two bents bolted together, with stringers added.. Many would shake their heads and say it isn't a real trestle, but I think a scale prototypical trestle would look too busy. In any event, my 'airy' trestle is whisper quiet, perhaps for the very reason you menioned; sound propagation through the pilings dirctly into the base of the layout can't occur when there aren't enough pilings.