Alternator A/C voltage question

[Bmwe5320023.0]

I'm trying to diagnose a nagging alternator whine with a new stereo install. Checking if the alternator is causing issues or not.
I've been trying to solve this for months and can't figure it out
https://www.diymobileaudio.com/threa...3#post-6033045
I'm trying to figure out if I should be a new alternator.

I just wanted to compare the readings and see if mine are out if whack.

I set the multimeter to AC, positive to alternator stud, negative to the battery or ground.
I'm getting a reading of about 0.150V AC

What I'm trying to find out is if this reading is normal or if I need a new alternator.