Diagnosis
A persistent buzzing or high-pitched whine usually points to coil whine from the power supply or the laser light source driver, not the cooling fans.
How to Fix It
First, try to isolate it. 1) With the projector on, gently press on different areas of the top and side casing (don't block vents). If the noise changes or stops when you press a specific spot, it could be a component vibrating against the chassis. 2) Check if the noise changes pitch when you switch picture modes (like from Vivid to Cinema) or when you display a very bright vs. a very dark scene. If it does, it's likely related to the power load of the light source.
If That Didn't Work
If the buzz is constant and loud, it's a component-level issue. Ensure the projector is on a stable, level surface and not sharing an outlet with a high-draw appliance like a fridge. If it persists, it's a defect. Document the noise with a video from your phone to share with support.
Heads Up
Don't confuse this with the initial 30-second fan spin-up when you turn it on, which is normal and louder. This is about an abnormal noise during steady operation. Ignoring a serious electrical buzz can lead to further failure.