How loud is that appliance?

Household noise is mostly in the 40–70 dB band, where nothing damages hearing but plenty ruins concentration.

The level Measured in

Almost exactly a washing machine

55 dB is louder than 4 of the 9 references on this page.

Reference figures are measurements and are rounded; the unit conversion behind them is exact.

Every reference on this page, with its size and its ratio to your number
Reference	Size	Yours ÷ theirs
a quiet bedroom at night	25 dB	2.2×
a fridge humming	40 dB	1.38×
a quiet dishwasher	42 dB	1.31×
rain on a window	50 dB	1.1×
a washing machine	55 dB	1×
conversation	60 dB	0.917×
a vacuum cleaner	75 dB	0.733×
a food blender	88 dB	0.625×
a hairdryer	90 dB	0.611×

The WHO recommends bedroom noise stays below 30 dB at night; the average urban bedroom is nearer 35–40.
A "quiet" 42 dB dishwasher is only just above a fridge, but because it is a broadband hiss rather than a hum, it is far less noticeable.

Frequently asked

The WHO night noise guideline is 30 dB indoors for undisturbed sleep, with 40 dB as the level above which health effects become measurable.

Barely — 3 dB halves the sound energy but is around the threshold of perceptible change. A 10 dB reduction sounds like half as loud.