Is the sound coming from the speakers or the PC itself? The internal component most likely to make loud hissing noises and cause crashes/instability would be the PSU. Some GPUs, sometimes in conjunction with specific PSUs, also have issues with noisy VRMs.
The little system speaker is connected to the motherboard. Which tells the errors about pc components.
I can't tell you solution quickly. You need to check every component to solve this problem. Try another PSU. Another components. Figure out why this sound coming.