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G'day guys,
Got a water tank with a on-demand pump hooked up to it which has quite a loud high pitched whine when it operates. Have checked with the manufacturer and plumber and apparently this is normal. Was thinking of trying to soundproof it by building a box around it and lining the inside with foam and/or eggshell cartons. Just wondering if anyone had any better ideas.
Cheers
Anything solid over the pump will make a difference. I made a box for the FIL's pump out of 19mm ply with high density foam glued to the inside. I also had the lid hinged so that you could lift it up to check anything. FIL concreted two loops of wire in to concrete base so he could use some bungee cords inside the box to hold it down. These could be easily removed to lift the box off for repairs/servicing etc.
You might need to make two boxes that nest over the pump motor. Generally, the heavier the material the better. also,I read somewhere that you need to make the sound waves change direction at least twice for good attenuation. Don't forget motor cooling.
Sand bags
Thanks for the replies. Anyone had any problems with overheating the pump. Ours is under the house so plenty of shade, but still have doubts about the summertime. Cheers:)
Try your local coolroom maker and ask him if he has any scrap bits he doesn't want, being styrofoam, it costs him to dispose of, so any he can get rid of for free saves him, it is the al/foam/al or steel/foam/steel, either way it is moisture resistant and very good at sound proofing. At the worst he may charge you a few bucks, it is usually joined with extruded al, but you could just use al angle and silicon sealant with tek screw or rivets. Don't forget to put some vents into it.
We have big and small vacuum pumps at work that operate from 2000 to 50,000 rpm which we constantly battle the noise from.
For typical electrical motor rpm. The degree of success depends on the volume and frequency of the sound coming from the pumps. We have had the most success using dense heavy barriers. Lead would be real good. For small pumps we have used bits of acoustic panelling (it's basically a fairly dense 50 mm chipboard same as is used in commerical room divider panels) which we formed into a box and place the pump inside this. In some situations this box is then placed inside another box on top of a couple of tubes of dense foam rubber lagging. We then ventilate the boxes using computer fans. Definitely worth doing
The 50,000 rpm pumps, . . . . well, you can't do much about them apart from providing ear plugs or placing them in another room and padding the room with around $20k worth of special acoustic panelling.
I have seen sound hoods from older printers that have been used with some success with vacuum pumps in laboratories. The hoods are lined with ripple foam, have heavy perspex lids and already have vents in either end. I saw one recently during a kerb side clean up on the north side of Brisbane. That sort of thing is effective inside but I'm not sure how it would stand up to outside use. There are products around specificaly built to sound insulate generators . They are sold through camping stores and one version is made of 50mm cold room wall panel material with ripple foam lining and vents. 3 - 4 metres from it and you can hardly hear it running.
I soundproofed my 6kVA backup generator at the house with a double-skinned box. The inner layer is cement sheet as used for wet-area flooring, which is lined with 2 layers of wool carpet. The outer layer is 20mm MDF which is mounted to a separate base from the inner box and braced with "studs" of MDF on 200mm centres. They don't have any points of contact anywhere. the lid is a double-skinned affair made as a torsion box from 20mm MDF and filled with sand. It is borne on the outer skin and hinged with a couple of gas struts from a van rear door to help lift it (it weighs over 100kg).Quote:
Originally Posted by Flyboy
Ventilation is provided by inlet and exhaust ducts about 200 square, which are made of MDF and also lined with wool carpet. These are mounted to the outside of the MDF box and enter the enclosure without touching the cement sheet. They double back on themselves 4 times. There is a good quality exhaust fan blowing into the inlet tract and no fan on the exhaust. The engine exhaust enters a 2" exhaust pipe which is rubber-mounted inside the exhaust duct and silenced by a catalytic convertor and muffler (off a subaru, if that helps). The genny frame is mouted to the floor on 4 rubber engine mounts.
The unsilenced noise of the genny is 79dBA at 1m, which makes it too loud to hear the TV in the lounge-room directly above. The silencing reduces it to the point at which it is comfortable to work using the lid of the enclosure as a torsion box and to talk normally while doing so. I'm guessing that this arrangement achieves at least 30dB of attenuation, possibly more.
The whole thing, not including waste due to false starts, cost me about $400. I tried steel for the inner lining initially, but found too many unwanted harmonics and weird emergent noises which managed to get through the outer skin. If I'd had the money, I would have invested in some of that lead-filled accoustic curtaining, but it's as dear as poison.
To sum up: the critical factors are mass, isolation of the inner skin from the outer and damping of reflected sound. How you achieve that is the fun bit.