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What is the high speed fan sound

Hi,
I have a 2008 Toyota Rav4 basic model. I periodically hear high speed fan sound coming from the car. Like every minute it speeds up for about 10 seconds. The RPM gauge doesn’t go up so i believe it’s the fan speeds up, not the engine. Even under cool weather with no AC on and no fan turn on. This usually happen after the car is turned on for over 30 minutes or so.
I have uploaded the video. You might barely hear it. But in the beginning of the video, you can notice the fan speeds up then almost at the end of the video, It quiets down.

Can you post the ECT read from a scan tool at the point where fans turn on?
If around 200 it would signal the ECM to turn on the high speed fans.

The electric radiator fan may turning on, as suggested above. On my Corolla normally that fan doesn’t turn on except in stop and go city driving and long idles.