What is causing the 5.5 kHz noise in my recording setup

Question

Recently I noticed a high pitched noise in my recording setup in my new house, 5.5 kHz to be precise as you can see in the image below of me playing a bass note. This noise only is present when actually playing a sound. You can see the noise stopped when I muted the string.

I've tried to figure out what is causing this noise. The noise is present on both the XLR and the jack input on my Roland Tri-Capture, it does not matter which instrument I am recording (electric drums, bass guitar, electric guitar, acoustic guitar, vocals). I have tried unplugging all other electronic equipment from the power strip of the PC (except the PC and the monitor) and change to a different power strip and a different outlet but that didn't change anything.

Somewhere someone had a noise that changed pitch when he changed the sample rate between 48 kHz and 44.1 kHz, my noise stays the same regardless of the sample rate.

What are other steps I can take to find the source of this noise? Or any ideas how to get rid of the noise (aside from EQ'ing it)?

Find the WAV of the sample here.

Answer 1

This is a broad sweep at the issue, some guesswork & experimentation required.

First of all, if you have an alternative DAC try it, no matter how basic, just to eliminate the simplest explanation.

Secondly - if anything has batteries, replace them.

Up at 5k, it's unlikely to be directly related to 'mains hum' itself, grounding issue etc.
A very simple test for 'mains hum' is hold the strings, let go the strings, see if the sound changes. It's worth a go, but I don't think this is going to be the root cause. It may be acting as a radio, though, picking up leakage from somewhere nearby, so the second test would be to rotate yourself & guitar & see if pointing in a certain direction changes anything.

I think the main possibility is going to be a switch-mode power supply. These would be anything with a 'wall wart' or such as computer screens, lighting circuits & laptops. These things can be producing RF at anything from a few KHz to well outside audible range.

Screen & lights are the simplest to test for, because the computer will still work without the screen on - record something with the screen unplugged from the wall & all lights off.

After that it gets harder, because not all switch-mode PSUs are simple 'wall warts'. There may also be one on a desktop computer's PSU or one in even an ostensibly mains-powered screen.
If it's a laptop, simple - record on battery power & see if it goes away.

For a desktop, if you got this far with no discernible change, then I'd be looking at its power supply - but there I have no method for testing; I'm not an electronics guy.

If you do find the source & it's not easily replaceable, then your options come down to distancing it from anything that can pick it up, or something like a Faraday cage.

Answer 2

5.5kHz is suspiciously close to a fraction of 44100Hz, a typical sampling frequency. This could be a resampling artifact if your audio interface is working with 44.1kHz and your DAW with 48kHz or vice versa.