Edit: solved! https://youtu.be/VVQz6jE3X50?si=qkItmXh5HbkKpZ8x

So it's somewhat old, as far as video memes are concerned. I think it was a vine.

There is one guy in frame. There is a high pitched tone playing. Maybe a fire alarm or something.

The guy says something like "hey does anyone hear that? Kinda sounds like aaaaaaAAAAAA".

He attempts to mimic the obnoxious sound, too low of a pitch at first, but adjusts upwards to nearly match it right as the video ends.

He holds his arm up with his hand horizontal as if to describe the pitch of the sound as he tries.

All of this is only maybe 5-6 seconds long.

I cannot find it. I have searched high and low. Google has failed me, or rather my googling skills have failed me.