how do DW manufacturers measure volume levels?

Derek87February 3, 2012

i'm curious...

we just replaced a GE Profile that supposedly was a 58db model, but in reality when going full bore, was about 70db standing in front of the dishwasher when it was doing it's "grinding thing."

our new Bosch we received yesterday is rated at 42db. it's MUCH quieter than the GE but by measurement, it still is in the low 50s at its loudest when water is hitting against a metal bowl inside the dishwasher and i didn't measure the sound level when it drains into the sink above the disposer, but i'm guessing that too is above 42db.

are these ratings largely a function of the ability of the cabinet/floor to absorb noise, etc? it would seem that where a dishwasher is installed would play pretty big role.

on the other hand, it seems uniform testing/spec would take a unit freestanding on a floor and put a mike/sound level meter X feet away and measure the volume. maybe the 42/58 db ratings we see on our two different dishwashers are from some distance closer to 5-10 feet?

not complaining, really...this is more just curiousity. funny thing: while i definitely know the DW is on now, even with the Bosch, when the fridge is running, i now notice how loud it is, not the Bosch dishwasher. that's progress! :)

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good question !

there is no industry standard, and few ,if any, manufacturers will tell you how they do it.

    Bookmark   February 3, 2012 at 6:54PM
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Quietness is usually a function of price. An expensive and noisy model will not be long on the market.

    Bookmark   February 4, 2012 at 10:07AM
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Derek: I'm so glad you posted about your experiences. As you know, we have the same DW, and it's not as quiet as we expected. My sister has an older (and a bit less expensive) model that you almost cannot hear when it is running. With ours, we hear it: as you said, when it empties and when water hits a metal bowl/pan.

It IS quieter than our 14 year old Bosch, but not the super quiet we had expected. We had wondered if the reason is that the DW sticks out from the cabinets about 1". We tried to get the installer to place it flush with the other cabinetry, but that just didn't happen. I've wondered whether it would be quieter if it were further back -- less noise leak? (In hindsight, we should have used our regular plumber instead of the appliance store's installer. Who knew?!)

In any case, what about your installation? Is it flush with your other cabinets? If so, then we're wrong in our diagnosis. Again, it's not obnoxiously loud; just louder than we had expected. But, as you say, not louder than the refrig.

BTW, to your question about db ratings ... at one point we were considering a Viking DW. We couldn't find a db rating and emailed the company. The response was that Viking did not test or provide that info. We didn't know if that was because their DW were louder than others in the same price range or if there just was no standard and so the manufacturer supplied ratings were pretty much meaningless.

    Bookmark   February 4, 2012 at 6:03PM
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kashmi, et al.

our DW is installed pretty flush with the cabinets (24" from the wall), with the handle sticking out. it's not perfectly flush because our cabinets aren't level (they are somewhat bowed out so the dishwasher face isn't perfectly flush with the cabinet. this is confirmed with a level: the bosch is perfectly level in all directions but the cabinets are not.)

so i've done some more research and investigation and here are some of my hypotheses/findings:

- i had been accidentally using a C-weighting on my sound level which has the Bosch checking in at 56-59db at it's loudest. but if i shift to A-weighting, which i'm sure Bosch would do (reduces the effective recorded volume measured for lower frequencies), the DW falls belows my sound level meters measurement threshold: it is below 50db standing 1-2 ft away from the front of the dishwasher.

- most of the sound is coming from beneath the dishwasher from the area around the toe kick. the volume goes up a significant amount if one measures at the level near the floor and even with A-weighting, i get a measurement of 54db (ie, measurable with my sound level meter)

- water being emptied out into the drain just above the disposer is louder too, but i don't think that is the dishwasher's fault and is unavoidable without a dedicated drain or something rigged to go below the disposer.

my conclusion: i may not be getting 42db (that may be attained with water not hitting any dishes, but it's probably performing to "spec" and that the 42 db is probably measured a few feet from the unit at standing level with nothing in the dishwasher. i do think some measure of sound could be further reduced by putting some sort of insulated toe kick below. that would surely help some of the noise.

i'm surprised your sister's older model is quieter, but it could be slightly a function of installation and perhaps ambient noise?

hope this helps. i'll have to make a few more measurement to satisfy my ardent curiosity (that's what i get for being a scientist for my day job), but i feel a bit better that the dishwasher is doing what it is supposed to as far as sound levels are concerned.

you owe it to yourself to buy or borrow a sound level meter to see if you 1" is affecting things. you still may be able to reduce the volume with it set back further, but it's hard to deduce with out any objective measures of the sound level.

    Bookmark   February 5, 2012 at 12:04AM
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