[housecat]

My manual transmission 2014 BRZ makes a rattling/flapping noise sometimes between 5mph and 30mph when I am rolling in neutral. The most difficult thing about this noise is that it seems to happen randomly, sometimes it happens and sometimes it won't happen. Here is what I've noticed:

The noise sometimes happens while I'm braking
The noise sometimes happens when I'm NOT braking
The noise sometimes does not happen at all.
The noise only happens in neutral at idle RPM
The noise happens while driving straight, not turning
The noise sounds like it's coming from under the hood in front of the driver
The noise started happening around 4000 miles on the odometer
The noise started happening once summer began and I used the A/C more often
I've never heard the noise happen when the A/C is turned OFF (I need to test this more)
The idle RPM seems fine when the noise happens (tachometer reads ~600rpm)
The shift knob does NOT rattle with the noise
The car doesn't shake with the noise

Here is a video of the rattling (you will need to turn up your volume to hear it).
[ame="https://www.youtube.com/watch?v=xWO3pzi1ICU"]Manual BRZ flapping rattling noise while rolling in idle - YouTube[/ame]

I suspect that the rattling is coming from the compressor for the A/C turning on while the car is rolling in neutral at idle rpm. Maybe the compressor lags on the engine and causes that flapping noise. The workers at my Subaru dealership couldn't figure out what was causing this noise. However, one worker who rode with me thinks the noise does not sound mechanical, rather it sounds like something is flapping around. We agreed that I would check back with them later, and if the noise continues or gets worse, we would test drive a BRZ on their lot to see if other BRZ's make that noise. I have made no changes to my BRZ besides a K&N air filter and mudflaps, but I'm very sure neither of those things are causing the noise.

My questions are:
Does anyone else's BRZ/FRS make this rattling noise?
Is this rattling noise a symptom of a serious problem?
Can this rattling be ignored, like we ignore the idle chirping/cricket noise?
Do you know what is causing this noise?

Thanks