Diagnosis
A loose or misaligned pre-filter frame is the most common cause. The high airflow on Turbo (Speed 4) vibrates the plastic frame, creating a resonant buzz.
How to Fix It
Power off and unplug the unit. Remove the front panel and the pre-filter. Ensure the pre-filter's plastic frame is perfectly seated with all clips engaged. Reinstall the front panel, pressing firmly along all edges until you hear a uniform click.
If That Didn't Work
Inspect the rear grille for foreign objects. Debris like paper or plastic can get sucked against the intake, causing fan blade noise. Also check that the unit is on a perfectly level, hard surface. Flooring can amplify vibrations.
Heads Up
The Medify MA-40 V2.0 has a brushless DC motor. A high-pitched electrical whine on lower speeds is not typical and may indicate a motor or control board issue.