I was developing a seekable implementation of AES and when I ran it; a high pitched noise started coming from inside my computer.
I know it was NOT the hard drive because there was hardly any hard disk activity at all, and I had recently replaced my hard drive. This seems to happen when I memcpy a huge array of bytes from one location in RAM to another, then delete it, and refill the buffer with data from a MemoryStream.
It's such a high pitch that some people can't hear the noise. It's not coming from my speaker, and I have no modem or motherboard speaker in my computer that could be making the noise. What could be causing this noise, and why would it only happen when running huge memcpy operations?
Some motherboards allow variable loading on their supplied power to devices, which use high frequency voltage regulators. These are similar to the VRMs on your graphics card. Under load, the duty cycle and frequency of the voltage regulators ramp up to improve your system's stability (at the cost of more heat).
This can also present another side effect, a high-pitched whine. Unfortunately, it may be difficult to pin-point, but as you've said, you are using CUDA/OpenCL. I'll assume for arguments sake that you only implemented these as you yourself have a card that supports GPU computation,
so I would point my sights towards the GPU. (Update from question's author, offloading GPU computation has not helped)
Failing that, you might want to consider looking into the motherboard's power regulators (I know ASUS motherboards are usually quite customizable). It may be only a specific frequency which causes the noise you experience, and you may be able to set the VRM frequency manually.