The answer to 'air filter making noise' is that a noisy air filter is usually caused by the filter being clogged or obstructed. This can create air turbulence and vibration as the air is forced through the filter, leading to a rattling or buzzing sound. Common causes include dust buildup, pet hair, or debris getting stuck in the filter.
In most cases, the solution is simply to replace the air filter. Depending on your HVAC system and usage, air filters should generally be changed every 1-3 months. If the noise persists after replacing the filter, it could indicate a larger issue with the HVAC system that may require professional diagnosis and repair.