High pitched turbo like whine following rpms
 

So I am trying to figure out what's going on with my car. I have a 2013 sport Tech BRZ and today, a loud high pitched turbo like whine/whistle that follows the rpms appeared. My car also randomly shut off right before I noticed the noise while parked on a inclined driveway. I have heard that this could be my alternator dying but I haven't had any issues other than that so it would be hard to pin it on that. Here's a link to a video with the sound.

https://youtu.be/uswKlkAai4s



It's very high pitched and you can hear it come in around the 8 second mark. If you have any ideas on what this is please let me know! :)

i don't hear anything in the video.

what mods are done to the car, both mechanically or electrically?

The car has an aftermarket head unit and it seems that there's wiring for a sub going to the trunk. Other than that the car has a cat back exhaust and coilovers. The video doesn't capture the noise the best but around 10 secs you should hear a faint high pitched turbo like sound.

so you didn't install it? but it just started randomly?

the whine is a ground loop. it means that there's either a bad ground, or more than one component to the audio system and there's a voltage potential between the grounding points of the components. it shows itself by presenting an audible tone as voltage swings between the different grounding points.

pull out the head unit, make sure that the black wire in the head unit wiring harness is connected to solid metal within the dash.

it might not hurt to disconnect the sub wiring as well if you're not using it, or inspect the unused rca cables metal ends for touching metal where they shouldn't.

Yeah I bought the car as is and the noise just started today. That is great advice tho, I will pull the head unit out tomorrow and I'll update on the situation.
Thanks!

I am guessing feedback from the audio setup. Engine sounds normal to me

Alright so plot twist, I checked everything out and nothing changed, so then I started looking at other sources for the noise.

https://youtu.be/AvGCZzSOFQk

I think it might actually be an exhaust leak. Don't hear it in the engine bay but it's at its loudest underneath the car.

Opinions?

time to put it on jackstands and look the exhaust over

yes I can hear it, sounds normal.