7+ / 256 / Matte Black / TMobile/GSM/Intel
Apple sent me a replacement phone. Original phone was Week 37. Replacement was Week 38.
They arrange an advanced replacement by calling 1800-apl-care, and put a temporary hold for the full value on my credit card until i return the original.
The hissing on the original week 37 was plainly audible even without 'stressing' the cpu, and was of course louder when stressing the CPU.
I never noticed the hissing of the 6S+ before, but after this whole thread, I decided to go and check -- yes, it does make a very slight hiss in the same spot if i put it right up to my ear, but honestly if i wasn't looking for it i would never hear it.
IMHO, all iPhone 6S and 7's have hissing to some extent, and the slight hiss is 'normal and not a problem'.
The hissing on the defective 7+ was probably 10X louder than the 6S+. The replacement 7+ is the same level of quiet as the 6S+. I am very happy with the replacement.
In all honesty, this morning, before my replacement arrived, I had very low confidence, and assumed that I was going to end up having to return both the replacement phone and the original, and get a full refund. Fortunately, all is good and I am keeping the replacement.
Good luck to the rest of you, hopefully you manage to get a replacement to your satisfaction. I've seen others say 'only 10% of 7+ do not have the problem'. perhaps I should buy a lottery ticket today that I only needed to get one replacement.