My new build is completely stable until I attach the glass side panel, then one front fan starts making a low hum that travels through the desk like a musical instrument nobody ordered

The case is a mesh mid-tower with three 140 mm front intakes and two exhaust fans. With the side panel removed, every fan sounds normal. Once the glass is attached, the middle intake produces a low pulsing hum between roughly 800 and 950 RPM. Light pressure on the glass stops it immediately.

Temperatures are fine, no cable touches a blade, and loosening the panel screws helped only slightly. Is this likely the panel resonating with that fan, or does attaching the glass change airflow enough to create the noise? I’m deciding between rubber washers, moving the fan a few milimeters, or simply avoiding that RPM range.