Intermittent high pitched whistling sound

I've got a 2.7 2021 Taco, just a week old. Three or four times, I've heard a quiet, high pitched whistling sound - sounds a little like a flute - that lasts about 2 seconds and sounds like it's coming from the engine or just behind the dash, toward the middle or passenger side. Has anyone else heard this? Any idea what it is?

 

https://www.tacomaworld.com/threads/whine-during-acceleration-update-finally-got-it-on-video.672022/

Does it happen when the AC in on? AC expansion valve resonance? Mine makes a similar sound to the video in that thread.

 

Extremely common, especially shortly after starting the truck and turning on the AC.

 

I haven't had the truck long enough to see a pattern, but based on your response and others, I'll be watching for that.

 

Never heard that in my 2017 but my 2020 definitely has this. Girlfriend thinks it's a turbo.

For me, it really shows as I accelerate, just like the video in the link @pjtx808 posted.

 

Mine is more pronounced under hard acceleration. I searched and saved several threads about it on this website trying to figure out what the sound was.

https://www.tacomaworld.com/threads/3rd-gen-tacoma-a-c-noise.550627/ (Massive thread - it's a discussion related to two separate sounds from the AC, the whistle and a "Darth Vader" breathing sound)

https://www.tacomaworld.com/threads/a-c-compressor-noise.497694/

https://www.tacomaworld.com/threads/help-me-out-what-is-this-noise.440062/

Mostly Toyota faults it as "normal" operation. In one of those threads a guy had his entire AC replaced (compressor, lines, etc.) and it went away. Another stated a Toyota service advisor told them that it was low on compressor oil and that's why it was making the noise. It has something to do with how Toyota designed the AC expansion valve in our trucks versus how most manufacturers do it.

Whistles go woo woo.

I thought maybe at first it was my transmission because that's the area it sounded like it was coming from. Then found those threads related to the sound I was hearing being the AC and chalked it up to being that. The truck had less than 1,000 miles on it when I first heard it.

 

Mine does it in second and third gear, from previous vehicles i just assume it's the air in air box or filter. Only around 2500-3100 rpms.