Ten to 15 years ago, dishwashers whooshed and washed and clunked and clanged with the vigor of a pile driver. It was annoying, but most people didn’t know it was possible to wash any other way. Dishwashers were loud, a Bush or Clinton was running for president, and everyone was excited for the new James Bond and Star Wars films.
Over the past decade or so, things have changed—at least when it comes to dishwashers. While there are certainly some stragglers, most name-brand dishwashers on the market today are quiet enough to run in a library. Typically, they range from 45 to 50 decibels—roughly the noise level of typing on a keyboard, and just below the threshold needed to wake someone up.
Now compare that to dishwashers from the mid-2000s. Those machines averaged about 60 decibels—just below the sound level of a vacuum. So today’s machines are much quieter, but the trend has had an interesting effect on consumers: Shoppers tend to overvalue the significance of the industry standard noise rating—the decibel A-weighting, or dBA.
The dBA rating is complicated, but it basically boils down to this: Compared to straight-up decibels (dB), dBA puts emphasis on noises that we hear most clearly and de-emphasizes sounds that are harder to hear. The result is a rating that should, in theory, give shoppers a better idea of how much their dishwasher will annoy them.
But how did a quiet dishwasher become the envy of homeowners everywhere, and just how quiet is quiet enough?
A Quieter Kitchen
It was actually a German brand, Bosch, that first got Americans thinking about sound back in the early 2000s. The manufacturer already had a line of quiet dishwashers in the European market, so it had a leg up when it came to developing new models for quiet-hungry American buyers.
In short, Bosch anticipated a need that customers didn’t know they had. Americans were starting to spend a lot more time in their kitchens, thanks the rediscovery of cooking via foodie culture and the growth of the “open kitchen” concept. Suddenly, a demand for quieter dishwashers was born.
The German giant met that need by fundamentally redesigning the dishwasher. Bosch engineers first incorporated a solid base made of heavy-duty plastic—the same material used in football helmets. They also installed a sensor-based drain pump that only ran when it detected the presence of water, eliminating much of the loud sucking noise heard during draining. Bosch also redesigned the hydraulic system, introduced a new filtration system to replace the hard waste disposer, and began using two motors instead of one to spread the work load.
(Not long after Bosch revolutionized the industry, a few retailers partnered with a sound lab to develop a standard measurement of dishwasher noise output. That’s the reason for the ubiquitous dBA ratings you’ll see in stores, in ads, and online—we’ll explain those later.)
The result was a line of “SuperSilence” dishwashers that, today, operate in the range of 38-46 dBA. It also led to a race for the lowest possible sound rating. That’s why Bosch’s primary competitor, Miele, pushed hard to hit an impressive 37 dBA with its Futura Diamond model. Using a specific “Extra Quiet” mode, it limits mechanical action and prolongs the length of its wash cycles. In other words, it’ll wash your dishes silently while you sleep, but it may take all night.
“Although there are peaks and valleys in measuring the sound levels during a wash cycle, we have managed to suppress even the portions of the cycle where the pump and drain noises are at their highest, turning them into a low-pitched hum,” said Hiroko Kawaguchi, a product development manager at Miele.