Today I arrived on site Initial Assessment: Investigated vibration noise reported in the AHU attic. Zone Identification: Confirmed the equipment services the heating and AC system. Fault Diagnosis: Identified the noise source as originating from the ductwork. Resolution: Discovered a dirty filter in the return ductwork. When arriving at the client's property. The client explained to me that he occasionally hears a very loud noise in the AHU of the attic. The client described the noise as a vibration sound. I proceeded to verify the system. I found a very dirty air filter in the return box of the master bedroom. 20x25x4 I removed the dirty filter from the return box. This unit also has a filter 20x25x4 in the return box of the unit. I also found the blower wheel of the unit full of dust. I showed him and recommended the client to consider doing the deep cleaning of this unit. I informed the client that I would send him the status to do the deep cleaning blower of the attic u