My Classic 2 is no louder than say an XBox 360. I can remember though powering up the Mac Plus years ago, and being amazed at how silent it was. Other than the CRT buzz I could hear (BBC Micro monitors used to be bad for this).

My desktop homebuilt AMD system had a noisy fan pulled off a Compaq. I bought a "silent" fan from Maplin and it was just as noisy. Until I noticed the extra attachment for the power supply cable. Thought it was just an extension, plugged it in and it brought the noise down.

That extension cable - It just had an inline resistor!