Switches of different types, mounted onto keyboards with different designs and materials, certainly make different levels and types of noise, and because of that, some try to measure the decibel level of the switches on a keyboard.
There is no point to measuring decibel level by hand, though, because each person will bang the keys with different levels of force. Even if the same person performed the test the same way each time, he or she would be unable to strike the keys in a consistent manner each time. And even if this was possible, at best you would be achieving only a baseline, not an objective decibel level that anyone else could replicate.
However, the audio experience of a keyboard is important. What is more important than loudness, though, is the quality of the sound being produced.
For example, a Red switch does not sound like a Blue switch. They have different mechanisms, and therefore they have different sound qualities. Reds are linear and have a single clack sound, when you reach the bottom of the key travel, whereas Blues have an extra "click" during the travel. One may be perceived as "louder" than the other, but that's not really important here; what's more notable is the fact that one has an additional event in its travel, and it makes a certain type of sound. Besides, a great many factors affect noise, including switch materials, tolerances, lubrication, and so on.
Further, the design of the keyboard can affect the sound the switches make. A keyboard with a metal top plate and switches mounted directly on top will have different sound qualities than a keyboard with a plastic backplate and switches mounted into a "bowl" with a top panel covering up parts of the switches. This is not to mention how sound is affected by keycaps (the material they’re made from and its thickness), how well a keyboard chassis is assembled, and even whether or not the feet underneath are flipped out or not.
Therefore, our methodology concerning audio is to record a reviewer typing on a given keyboard, describe the sound qualities he or she perceives, and offer that recording so readers can listen for themselves.
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