While at home, I was able to see the V_in just fine. But it didn't reveal anything. So I swapped out my existing USB power supply for an IPad power adapter. Looking at the V_in, it is worse than the Anaker USB power adapter I bought. But the bigger deal is that it had NO effect on the noise.
So now I'll wait until everyone leaves the house and start flipping breakers to see if the noise is in my house.