Hi @Sloth,
The most likely scenario is that the increased noise output you hear is your system fans ramping up to handle the load ZBrush is placing on your CPU. Using fewer threads would also reduce CPU usage (and performance), and so reduce system load as well.
A reminder that ZBrush performance is mostly CPU-based. Unlike some other 3d programs, in most cases the GPU is not used. So even basic navigational actions are seen in the CPU burden. You can see heavy CPU usage just from constantly panning a relatively low poly model around the viewport for an extended period of time.
Most healthy systems can handle those kind of CPU spikes. But if your system has marginal cooling, high CPU use could be generating a lot of heat that your fans are struggling to deal with. Older devices with a lot of dust accumulation can also begin to experience heat issues, and a program like ZBrush will expose this by placing the CPU under heavy load.
While there certainly could be a noise issue associated with your SSD hardware, this would tend to be affected by the size of the file you are working with and not the thread count. Depending on available system memory, the SSD may need to be accessed more frequently when working with a large file to write virtual memory files to your scratch disk.
This is a known issue in the current release of ZBrush.
Please be sure to contact Maxon Support for all technical issues with your ZBrush installation, as well as to report any bugs. We can’t conduct technical support in the community usage questions forum, so our ability to assist you here is limited.
Thank you! 
