Noise in a shared home

A noise figure is useful when it states three things together: a number in decibels, the distance it was measured at, and the speed and load the device was running under.

Distance matters because sound falls by roughly six decibels each time the distance doubles. Without its conditions, a figure cannot be compared with another device, or even with the same device a year later.

A motor with nothing to work against makes a different sound from one that is working. A figure taken while the device runs free describes a condition nobody uses.

Most people also use a speed well below the maximum, which is another reason a single top figure says little on its own.

Structure-borne sound. A device resting on a bed frame passes vibration into the frame, the floor and the wall, and the same device on a folded towel does not. That difference is often larger than the difference between two devices.

The wall behind it, the floor under it and whether the building is timber or masonry all play a part. A device is quiet or loud somewhere, never simply quiet or loud.

Put something soft and heavy underneath. A folded towel or a foam mat breaks the path into the floor and costs nothing.

Move the device away from a shared wall before turning it down, because distance and decoupling do more than speed does.

Try it at the speed you will really use and at the time of day you will use it. A device that goes unnoticed in the afternoon may be noticed at midnight, because the background has changed.