Some of my modules are located in central junction boxes in the ceiling with a lid and a light fixture mounted on top of it, but standing under it, I can still hear it. Other modules are mounted in junction boxes in the wall with a switch or an outlet mounted on top of it; Those I can hear throughout the room. A few modules are mounted in the base of a floor or desk lamp and one of those is on my night stand so it's not an imaginary problem.
To check my sanity I have removed one of loudest modules I could find and I've made a recording. Unfortunately I couldn't post here because the forum doesn't accept .wav files (Pieter?)
But I did a couple of measurements and it appears that these modules produce a very distictive sound: A high pitch sound of around 11kHz with a light rattle on it. Almost like a tiny, yet persistent cricket. It even briefly increases it's pitch periodically. Some modules are louder than others, but the sound is the same. <b>Warning</b>: Once you know what they sound like, you will hear them everywhere, no matter how soft they are. So if you never heard it, don't go looking for the sound and don't listen to my recording or you will unwillingly train yourself to hear it.
But looking at the spectrum is quite safe. The illustration below shows the full audible spectrum and the xanura sound clearly stands out. The waterfall diagram shows the periodic frequency shift:
When zooming in on the spectrum, the rattle can be explained with of the bandwidth of the sound:
Does anybody experience similar noises?
