2022 G26 M440ix high frequency cabin noise

I’ve got a 16 kHz noise (measured with spectrum analyzer) in my cabin whilst the HVAC is enabled and it drives me nuts. If the fans are completely off, you can hear it abruptly cease. Personally sounds electrical, it’s a relatively pure tone. If it was constant, it would be easy to convince yourself it was tinnitus, but being able to disable it with the climate control makes it very obvious. if anyone else has encountered this and found the cause, or whether or not replacing the entire hexagonal HVAC module/panel has resolved their issue.

I will bring it to the dealer, but given the nature of the high frequency it’s hit or miss on whether or not a technician will be able to hear it and I’d rather give them some sort of basis to go off of. I’ve put my ears up to the HK tweeters to see if it could be some sort of ground related issue that caused the tone through the speakers, but it does not seem to be originating from there at all.

The one interesting thing is that it does not seem to have any dependence on A/C or heating versus cooling, however the noise did not begin until the temperatures transitioned from freezing to spring

(AI summary below, easier than retyping all of the diagnostics I’ve tried):

•	Noise type: steady, narrowband, high-pitched electrical tone

•	Measured frequency: \~16.0 kHz, \~40-45 dB 

•	State dependence: present whenever HVAC is enabled; disappears when HVAC is disabled

•	Audio evidence: recorded clip showed the \~16 kHz component remained stable while HVAC was on and dropped out in the last \~5 seconds when HVAC was turned off

•	Fan speed: no meaningful change with fan speed increase or decrease

•	Temperature setting: no meaningful change with temperature increase or decrease

•	A/C setting: no meaningful change with A/C explicitly on or off

•	Vent selection / airflow mode: no meaningful change in the steady high-frequency tone across vent mode combinations

•	SYNC vs dual-zone: no meaningful change with synchronized vs asynchronous climate settings

•	Rear climate: no meaningful change with rear seat climate enabled or disabled

•	iDrive reset: performed; no change

•	Engine sound settings: changing cabin engine noise / engine sound settings made no difference

•	Localization: audible throughout the cabin, with similar apparent loudness near the passenger-side footwell and directly in front of the small HVAC display/control screen. Difficult to determine exact directionality.