Why is there no sound in FaceTime?

Question

macOS

Hello.
A very strange problem.
There is a Macbook Pro, Late 2013. i7 2.6, 16 gig of RAM
OS X Yosemite (the same problems on the El Capitan beta)
The essence of the problem. The sound in FaceTime is very dependent on the load on the processor. If nothing is running, then everything is fine. If the processor is at least slightly loaded (chrome is open with 5-6 tabs, or a couple of unicorn instances are running), then there is no sound. I can't hear anyone, and they can't hear me. Both FaceTime <-> FaceTime and FaceTime <-> cellular calls (via iPhone) are equally affected. When calling from an iPad through an iPhone, there is no such problem.
I don't know which way to dig at all.
When calling through an iPhone, the utun0 interface is created. I did a tcpdump dump to a file. I called the autoinformer, so the length of the conversation was the same every time, 27 seconds. At rest, tcpdump writes about 30% more packets than when the processor is busy with something. The dump file size is correspondingly larger as well.
I made a FaceTime call through an iPhone to my wife's phone when the computer was under load. I counted the numbers in order, after 15 seconds I removed the loading process. After 10-15 seconds after that, on the phone I began to hear the numbers that I dictated 30 seconds ago.
If you call without a load and then add it, you can hear how the frames begin to fall out first, then silence ...
I have no idea where to dig ...

Answer 1

SMC, PRAM and NRAM dropped?
Take it to a normal service, let them clean it, I think something may be short on the motherboard if there was moisture.
There may be water, because when the processor is under load, the consumption increases.