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It is likely that the walls are acting as drum skins. They seem to have similar resonances, from your accounts.
This is not going to be an inexpensive fix, unless you engage the right expert.
Your problem will be in finding a functional fix as few folks know what they are doing in the case of ultra low frequencies. This is the hard reality of sound and noise control. It being so prevalent that the measurement weighting standards totally ignore these sounds, as they don’t know how to deal with them.
Or put the fence back up.
"The whole building is being shaken, especially upper floors. This is an obvious case where you would ideally want the entire building up on springs."
You mean suspended like a Linn turntable?
The practical solution is to isolate the speakers and your stands using a spring based solution such as the Townshend products, or for that matter Geoff’s springs. If you are feeling flush (very) an active isolation system such as the Herzan tables would also be very effective ... as others have noted this sort of interference is endemic and most audiophiles have never adressed it
Geoff -- as far as I am aware no turntable suspension (barring ones such as the Dohmann Helix with an integrated minus-K isolation system) has a suspension that deals with vibration outside the audio range. Agreed the Linn is exceptionally floppy (i.e. high resonant frequency) but most are like that - my EAR has among the stiffest springs I know but again is no use against the sub 10Hz issues we are talking about here
It does seem however that the OP has a secondary issue in so far as the room itself is exacerbating the sub-sonic issues. Bass traps will not help as they are also tuned to the audio range and cannot deal with sub 10Hz (think how large such a bass trap would need to be)
I wonder if the issue is the floor acting as a resonator then mass loading the floor in the appropriate manner might break things up?
Failing that as others have suggested an isolation fence could be a good idea -- many suppliers make such a thing but again it will not deal with the sub-sonic problems ...
If a suspension is exceptionally floppy it means the resonance frequency is low, not high. If the suspension is very stiff it means the Fr is relatively high. Resonant frequency is proportional to the square root of spring rate (all springs total). Almost all isolations systems extant deal with vibration with frequencies outside the audio range, I.e., seismic vibration, in range 0-20 Hz. Like that produced by Walmart trucks.
Folkfreak and all, the big problem is the room resonating. It is not a problem caused by speakers, although I am sure it affects both speakers and turntable.
I was hoping I would be able to do something inside the room like Bass Traps. I will look into the issue via the internet, but like all, I was hoping for a magic bullet, I had not thought of. I guess I have to put the fence back up or live with it.
@acman3 we get it! All of the responses you received were relating to external subsonic vibration. That is the problem you are trying to work with and that is what springs, Herzans and the like will deal with. You cannot use a bass trap -- it would have to absolutely enormous!
Our solutions are practical in so far as if it proves impossible to remove the source of the subsonic issues (which frankly it will be, subsonic vibration is present all of the time from mini earthquakes and the like) then the only solution is to isolate the audio equipment from its effect which the solutions we are suggesting will do.
Does your city/county have a noise abatement officer? If so, ask the officer to stop by when the trucks are there so you can have your complaint verified. Then take it up with WalMart management. See if you can convince them to put up a sonic barrier on their side.
If not, move ,cause you'll never be satisfied trying to stop what's going on from inside the house. Don't waste time and money with bass traps, etc. 'cause none of that stuff was ever designed or intended to solve your dilemma.
Best of luck.
Thanks for ALL the ideas.
I know the trucks are not allowed to idle for longer than 5 minutes in my city, which they seem to ignore, but the only time I notice the problem is around 9:00 pm, on various odd days. On the first night when I was doing investigating and after discussing with night manager, the noise became intermittent, so I will try talking to the main store manager.
My hope with something like Bass Traps, was that since along the walls there is no problem, I could somehow get the nodes in the center of the room to cancel each other. Also, I was thinking it would be the only way to get bass traps in my living room, sorta two bird, one stone.:)
We have been discussing moving to a different city, farther away from the city. I guess it is time to decide.
elizabeth +1, that could very well be where the noise is filtering through: your window, which acts like a drum skin, or a passive radiator, and passes the noise right into your home. That, or the fence, which could be argued, prevented the noise from reaching your windows.
I'd google all the different ways to isolate all manner of noise abatement for windows, if after testing for it, like elizabeth suggests, proves to be the culprit. Maybe heavy duty double or triple pane windows that face Walmart.
All the best,
I appreciate all the ideas, and will play around with them in the next few weeks.
I was thinking today, why is the noise strongest in the middle of the rooms, with both rooms being different sizes. It dawned on me there is a fireplace insert in the center of the two rooms. It is open to the living room and backs up to the bedroom. I am going to check that out a little better too.
There is a wall of double pane windows, with shutters, facing in the direction of the Walmart, in both rooms, so I suspected that would be a problem. They have done a great job on cutting down on the noise, and give us what light we have in these areas. The house is fairly tight and that may hurt with internal resonance.
The strangest thing is I actually looked into the possibility of having a problem when taking down the fence and the several articles said a fence would have to be 12' tall to have an effect, due to the waves going around/over the fence. I guess they were wrong in this case.
I have been landscaping, and will add more plants along the fence, but the greenbelt is a forest, except for a gully in the center. I like more plants so no big deal.I have four 20' trees in the back yard, but only two in the line of sight of these rooms.