Low pitched humming sound at cold start idle

[sapphire black]

Hey everyone, wanting to ask if anyone has experienced the noise above.

This sounds like a low pitched humming sound like a wind instrument. Only occurred at cold start or partial cold start and goes away very quickly after driving for a few minutes, sound is consistent/independent of rpm. No perceived loss of power. It does not seem to be PCV or belt related as those sound much rougher and higher pitched. This is like a smooth consistent low pitch hum.

Next time I hear it I will take a video to post here. Planning to take it in for an inspection next week.

Thanks in advance, all advice is appreciated!