DIYbanter - View Single Post - How Quiet Can I Get From Boxing a Noisy Shop Vac?

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wrote:
The box I made initially had five 1 1/2" holes in the back of it for
exhaust ports. My vaccum exhaust its air from the canister into the
upper part of the space in the cube and I located the holes along the
bottom edge of the cube thinking that the interior air in the cube
would have to be more completely exchanged this way.

If I understand you correctly, the air outlet hole of the box is
actually far away from the actual air outlet of the shop vac itself. I
thought this might not help the air flow around the motor to cool the
motor. But now I think of this, I have a feeling that this probably
doesn't matter: The shop vac forces air through the motor to cool the
motor down and not depends on natural air venting; therefore, having a
shorter path between the motor and the air outlet probably is not
critical. On the other hand, having the motor far away from the air
outlet may have helped reducing the high pitch noise. I am just
guessing...

It works pretty well this way for me. Heat build up inside the cube is
completely acceptable with what I have. I think the thing to watch
for in your box is if there is much back preasure buldup in it when
the vaccum is running. I am sure different vaccums will have
different air flows through them when setting in an open room.
I discovered that if there is a large back preasure inside the
cube the peformance of the vaccum's suction in the intake
hose will be degraded.

I guess we can fix this "excessive back pressure" problem by enlarging
the air outlet, right?

The cube I am using actually has had two different vaccums in it. The
first shop vac was a 12 year old Sears that was on its last noisy leg
when I first tried reducing the noise by putting it in a box. I built
the box with more interior room than I needed for this vaccum because I
knew that this vaccum was not going to last too many more years. I
wanted a box that would not have to be rebuilt for a change of vaccums.
The first vaccum is now dead and I have bought another noisy Sears
12-15 amp shop vac. For some reason, the new vac sits much lower to the
ground than the old vaccum did and probably passes more air through it
than the old one did. Because it is much lower to the ground, it was
necessary to drill a new hole in the side of the box for the suction
hose to pass through. The hole I drilled in the side is the outside
diameter of the 2 1/2" hose that is standard for this vaccum. This
new vaccum probably needs the extra hole since I have observed that
there is air under very low preasure passing through it. Just check
your exhaust ports on the box you are building and make sure that the
air passing out through the holes (or through the port) you are
building is under very low preasure and that there is no signifigant
preasure buildup inside the box when the vaccum is running.

Conderning your question on the noise reduction. My box has worked so
well that as I said It has had two vaccums in it. The carpet on the
interior of the box probably contributes signifigantly to the noise
reduction. For me, the high pitch whine that is so typical of a cheap
shop vaccum is almost totally absent. What I hear is some noise from
the lower pitched sounds that the vaccum gives off. I do not have sound
measuring equiptment and am unable to give any science based accurate
measurements of the noise reduction. But, I maintain that you will be
able to talk to someone in your shop in a normal tone of voice or
listen to the radio without having to increase the radio volume
signifigantly nor will you have to turn the volume on the radio down
when you turn the vaccum off. I often use my vaccum attached to my
random orbital sander for long sanding sessions and the sander makes
much more noise than the vaccum.

I am very glad to hear that the noise of your shop vac is now
comparable to the noise from your random orbital sander. I find that
the noise from a random orbital sander is quite low and is quite
acceptable. Sound like I can keep my hope high in term of getting a
great reduction of noise from my shop vac.

The 1 1/4" vaccum hose that is used to attach to the sander
makes somewhat of a high pitched sound whistlening sound
when it pulls lose from the sander and the whistlening sound
of the vaccum hose is much louder than the shop vac running.

Because the cube that the shop vac is in is somewhat heavy, I have
purchased 18' of 2 1/2" vaccum hose and I move the hose to where I want
to use it instead of moving the vaccum. My cube is on casters, but
experience has shown that for me, I am more comfortable moving the hose
than moving the vaccum box. I also have adapters to attach various
tools to the 2 1/2' vaccum hose or a short length of 1 1/4" vaccum hose
to attach to various tools

Glad to hear that the suction of your shop vac is not impaired by the
18-ft long extension vaccum hose. I will definitely try a long hose
like yours; hopefully, I can keep the shop vac inside the garage and
run the extension hose to my boat (that is parked right outside the
garage).

You must be much stronger than I am. I find the box that I am building
_very_ heavy (it is made from 3/4" particle board). I have splitted
the box in half (a body and a lip) in order to minimize the weight of
each piece that I need to man-handle; but I still find it to be very
heavy. Anyway, I am pretty much giving up of the idea of moving the
shop vac and the box onto the boat -- too heavy to do this often. The
shop vac and the box will have to stay on the ground.

I liked this arrangement so well that I have build a cube to put my
Grizzley dust collector in. I have been disappointed in how large the
noise reduction has been for the dust collector. The box reduces the
noise but not nearly as much as it does for the shop vac Thinking about
why the dust collector noise reduction was not as dramatic as the shop
vaccum, I have come to several conclusions( None of which as of this
date have been proved).
1. The dust collector box was built out of 5/8" birch plywood,
2. The primary noise frequncies of the dust collector are much lower,
more energenic and more likely to pass through the box one way or
another,
3. I failed to line the interior of the dust collector box with carpet
or other sound deading material,
4 Because of the signifigant weight of the motor and fan, I am sure
that both of them will need to be futher isolated from the bottom of
the box in a way that lower pitched sound vibrations are not
transmitted to the box. They are currently bolted to the bottom of the
box.

I am sure I will eventually go back and make an attempt to reduce the
dust collection noise futher using improvements that are outlined in
the four unproven reasons above. When I do I will report on the
results if there is a large noise reduction in the dust collector.

I think you are right to say that the low pitch noise from a dust
collector is hard to reduce.

You may need to suspend the entire dust collector inside the box to
keep the virbation from transmitting out of the box. I think I read
something like that in one of the very popular DIY dust collection web
site (from Bill?).

Hope you will find a way to reduce the noise from your dust collector.

Jay Chan

wrote:
I have already partially finished building the body of the box (except
for the baffle air outlet). I am using 3/4" thick particle board. I
use particle board instead of MDF because particle board is cheap and
seem like it is dense enough; moreover, it is what the dust-collection
book recommends. Not sure if it is any better for the saw blade than
MDF though. But this box is really heavy (3/4" particle board). I
guess my idea of carrying it on and off the boat is not quite practical
afterall. I will have to leave it on the ground and use a long
extension hose to reach inside the boat.

Thanks for pointing out that the air flow volume is the key to keep the
motor cool. Would you please tell me how large the air outlet hole
that you have in your box? Then I can have something to base on.

How much quiet your shop vac is after you have housed it inside the box
that you built?

I will finish the body of the box quite soon. But I probably cannot
finish this project for quite a long time because I cannot find any
free carpet underlayment. Buying new carpet underlayment from home
center for three layers of insulation will cost me $75 -- this is more
than what I really want to spend on building the project. I will have
to wait until I come across a dumpster full of carpet underlayment to
finish this project. Meanwhile, I will have to make do with using some
left over fiberglass insulation as sound-dampening material.

Jay Chan

wrote:
I would like to make the following comments concerning my noisy shop
vac

1. I used 3/4" thick mdf to make my box because, in general, its
higher mass will deaden the high frequency sounds better than plywood.
I have a Sears shop vac and it gives off mostly high frequency sounds.
Also, a thiner plywood or partical board would not have worked as
well, but it would still reduce the noise considerably.
2. Cooling of the vaccum motor is dependent on the movement of air
into the cubical box(suction) and movement of air out of the
box(exhaust). The air comming out of the box will be warmer than the
air going into the box. The vaccum's cooling is dependent on a
sufficently large volume of air passing out of the box since the cube
acts as a thermal insulator surronding the vaccum motor. In use, the
temperature of the vaccum cleaner inside the cube will depend somewhat
on how large a volume of air the suction hose is able to pick up and
pass into the inside of the cube that the electrical motor is operating
in. You need to be sure that the suction is not completely block for
long periods of time. A portion of the electrical energy the vaccum
motor consumes is converted one way or another into heat that must be
exhausted to the exterior of the cube for long term cooling of the
vaccum motor.
wrote:
wrote:

I will use particle board instead of plywood to construct the box. I
am under the impression that dense material is better in term of
keeping the noise down. If this still cannot keep the noise down
enough, I will need to consider getting the expensive and quiet shop
vac from Fein.

Make sure you pad the bottom nice and thick. I don't know about density
as noise abater but I know solid wheels on a solid surface really
increases the vibration.

The better the lining is at sound deadening, and the thicker it is, the
better. The more room you give it to add soundproofing, the better. The
more I think about it, if you baffle the air flow out, and you really
pad those walls, you could probably get the noise down low enough so it
didn't make any more noise than an idling car.

I'd check it every few minutes to see how hot it was getting in there,
though. Best o' luck with that. :-)