Today I arrived on site AC System Inspection and Repair Identified noise issue at the 2nd floor AHU. Located the AC system for the 2nd floor. Found the return box duct flex was twisted. Observed the air filter was a 13 Merv. Upon arriving at the property, contact the client to access the property. The client told me how to access the property. The client mentioned that the system on the 2nd floor is making a noise in the AHU. I proceeded to verify the AHU. I found this unit making a noise. The cause of this noise came from the duct flex being gone and was causing an air flow restriction. I also found that the air filter is 13 Merv. I contacted the client and explained the situation. Re locate the duct flex, replace the air filter. The sound disappeared. I recommended the customer to consider using an 11 Merv air filter. The client mentioned that he would like to meet with the project manager to verify if a hard metal ductwork can be installed for the return box. I told the