Switch off the AC and listen carefully to where the sound is coming from.
Make sure the front cover is properly closed and not loose, as loose plastic can create vibration sounds.
Dust build-up in the filter can reduce airflow and create unusual sound while running.
Start the AC again and listen for the sound. A light airflow sound is normal, but rattling or buzzing is not.
If the sound continues or becomes louder, technician support may be required.
Regular cleaning helps prevent vibration and unusual AC noise.