Engine Noise? Help please

This noise is not new but has anyone figured out what causes it?

Observations:
Happens at several different speeds.
Happens at a point where you are decreasing throttle almost feathering after acceleration.
There is no point where you can make sound continuously.
Happens usually between 3rd and 4th gear but have heard it between 2nd and 3rd
Does not sound like the rear diff noise.
One person said it is 1320 hz wondered if it is resonant frequency associated with heat shields.
Will not occur while not moving.
Reminds me of sound made by passing air over a glass tube
Don't think is is the A-arm holes since it is engine dependent

My guess; a venturi sound in the carburetor and has to do with the valve timing changing at the point the engine load diminishes.

Here is what it sounds like.
https://youtu.be/mV76JHlTVl4

 

Pretty sure that's the air conditioner. Try turning it off and driving. Mine does the same thing.

 

Are you thinking it is the compressor? If that is true it could be demonstrated without driving. Having the AC off would change the engine load.

 

OP Do you have an aftermarket intake? My GTI used to have a harmonic on the intake tube at a certain RPM.

 

It's definitely the AC compressor.

 

I have that happen on mine all the time but have never been able to catch it on video!

 

Stock intake.

 

also saying it's the AC compressor. I can almost always make mine do it on command in the morning when I turn on the AC at the end of my road.