Central Vac silencer

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I want to truly silence my Hayden central vac. I bought a muffler for it, but it's not really of much use since I've already vented the exhaust to the outside via an unused dryer vent. The facts are that it's a high RPM motor and it whines and wakes people up when it's in use when someone's sleeping. My plan is to box it inside something lined with acoustical foam and to provide two auxilliary fans (one low mounted push, one high mounted pull and thermal monitoring) to keep the motor cool and shut if off if the temperature in the box gets too high. I know the motor's got a built in thermal shutoff, but since I am going to be running it in an abnormal environment and what a replacement costs, I'd feel safer with two.
I am going to make some preliminary and crude sound measurements wrapping in a different material to see if any has particularly good sound deadening properties. Anything I am missing? What sort of materials (I was thinking 3/4" ply and that bumpy acoustic foam) should I use? How much distance to leave around the unit for good airflow? What CFM rate? What sized fans? I intend to use 120MM 12V PC case fans, but I'm worried that a lot of sound will leak out through the fan ports. I thought perhaps "top hatting" them the way chimneys and vent pipes are covered would reduce the leakage, especially if the cap had some acoustical foam facing the fan.
Any thoughts appeciated. Any flames will be cheerfully ignored!
Bobby G.
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<stuff snipped>

That's a good idea and one I am ashamed to say I didn't put in my sketch!
Thanks!
-- Bobby G.
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I would talk to Hayden , I bet they know what is most cost effective and works. The Sound- frequency, frequencies, you are deadining have a wave length that some materials absorbe better than others and foam may not be as effective as something cheaper. An example of why you only hear bass from cars or homes that are to loud is the wave of the low frequency can be 3-4 feet long, and carpet stops the real high frequencies as they can be only 1/4" long. The frequency of the whine, Hayden or a musician could figure out, then an enclosure needs to be designed for that area of frequencies. I guess a 1" drywall box with 6" fiberglass batts open to the motor might be better and cheaper but i cant hear the vac from here, the fan idea and completely closing it is risky, you cant rely on the thermal cutoff in their unit for saftey. Maybe rubber mounting bushings of the vac would do alot as its probably vibrating the wall.
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Before I undertook all that work, I'd get a new, quieter unit. I have a 25 year old unit located in the basement and most of the noise in the living space comes from the head unit that sounds similar to a conventional vac, not the motor in the central vac.
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On Aug 15, 7:32am, snipped-for-privacy@optonline.net wrote:

Right I thought a main selling point is those were supposed to be quiet, could the instal be bad? but I wonder if its really noisy.
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<stuff snipped>

I'll be waiting for your check! (-: I think you've got a point in that I should try cheap solutions like a water heater blanket to see if that has any effect. New vacuum not an option since this is new, sort of. Not very many miles and was the top of the line at the time. It just sat in the box a long time before the preliminary work got done. Who doesn't have such a project waiting around their house?
-- Bobby G.
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wrote:

the
sleeping. <stuff snipped>
<<I would talk to Hayden , I bet they know what is most cost effective and works. The Sound- frequency, frequencies, you are deadining have a wave length that some materials absorbe better than others and foam may not be as effective as something cheaper. An example of why you only hear bass from cars or homes that are to loud is the wave of the low frequency can be 3-4 feet long, and carpet stops the real high frequencies as they can be only 1/4" long. The frequency of the whine, Hayden or a musician could figure out, then an enclosure needs to be designed for that area of frequencies. I guess a 1" drywall box with 6" fiberglass batts open to the motor might be better and cheaper but i cant hear the vac from here, the fan idea and completely closing it is risky, you cant rely on the thermal cutoff in their unit for saftey. Maybe rubber mounting bushings of the vac would do alot as its probably vibrating the wall.>>
Good points. Acoustics can be tricky. It's quite possible just wrapping the motor end of the assembly will reduce noise enough to not wake anyone. It's fairly quiet, and you can't really hear it if you're not near it except when the house is very quiet. If I do my own fans, I will monitor the internal temperature and kill power to the vac via relay if there's an overheat. An extra thermal shutoff can't hurt much.
Thanks for your input!
-- Bobby G.
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Would it be easier to use the vac when people are awake?
That said, you can use a bathroom exhaust fan, to draw the heat from the top of the room / closet where the vac resides. Also, please consider that the sound may be going out the bottom of the vac through the floor. So, lift the unit and put sound deadening under the unit.
--
Christopher A. Young
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Shift work. Not an option. If the foreclosures ramp up, might even have to "hot bunk" like they do on subs if homeless friends and relatives have to be taken in. Let us pray for economic recovery. (-:

It's hanging from a plate attached to a piece of 3/4 ply attached to cinder block wall. I am moving it, so I think I will use some of the big rubberized mounts I've seen in my junk pile but quite can't remember where I got them from. Like car motor mounts, just much smaller. Good point, though, to insulate the mountings as much as I can acoustically speaking.
-- Bobby G.
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Ah, shift work. I heard that. Having been a shift worker.
Mount on a foam pad is good idea -- camping section at Walmart, buy a foam sleeping pad for six bucks or so. Cut it up with a razor, to the right size for under your central vac.
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Christopher A. Young
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A central vac should not be making this much noise. Mine is in the garage, in a 2x2x3 wooden box (no fans in box), vented to the outside with a 4" duct. You cannot hear the unit inside the house at all, just the swish of the air through the cleaner nozzle. Barely audible outside.
You should not need fans in your soundproofing box. After all, you do not run your vacuum all day, maybe half an hour, unless you have a 10,000 sqft house :-).
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Walter
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It's mounted in the basement and that makes all the difference, noisewise. A high RPM motor of enough HP is gonna make noise naked to the world. Mine's not yet in a box, either, so that's two major differences between my install and yours and probably more than enough to make the difference, noisewise.
-- Bobby G.
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Robert Green wrote:

You may be trying to solve the wrong problem.
I'd put a timer on the electrical input so they thing won't even WORK during sleeping hours.
There's also an innovative fix involving three items: Pliers, blowtorch, and the person running the vacuum.
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Yea blowtorch the person running it at 2am
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in
thinking
I would use lead. You can get thin sheet lead in 1/32" that you can wrap around the noisy box and kill all of the sound.
--
Roger Shoaf
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Heavy carpeting works wonders, the stuff with a thick foam backing helps the most at the lower frequncies. I'd also contact the mfgr and see if they could tell you of other installations of your model in your area. Then go listen to a couple of those to see if yours is especially bad,
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wrapping
<<Heavy carpeting works wonders, the stuff with a thick foam backing helps the most at the lower frequncies. I'd also contact the mfgr and see if they could tell you of other installations of your model in your area. Then go listen to a couple of those to see if yours is especially bad,>>
Another good idea. Thanks. I have some kicking around that I could try.
-- Bobby G.
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wrapping
But it would make Superman suspicious and we all know how he loves to crash through cinder block walls when making an entrance. Good idea, but high risk.
I never thought of lead as absorbing sound waves, but it absorbs other waves quite well. I might look into acquiring a used X-ray apron. I'll bet that deadens sound and a torn up one could be had for cheap with a little searching. Thanks for the input.
-- Bobby G.
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Robert Green wrote:

You'll never get an FHA approved loan...
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