I have a single central air intake vent for the furnace (Goodman GMP050-3) which supplies my two-story townhouse. Unfortunately, this intake vent is located in my living room. Whenever the heater or AC is active, it sounds like a jet engine in the room. As per the pictures below, the furnace is only ~12" from the vent itself. Air intake comes via a 14x18" hole connected to the furnace by a metal duct. The hole is then covered by two 15x30x1 filters, and covered by a 30x30" grill.

As far as I can tell, the noise is entirely air flow - i.e. there does not seem to be any problem with vibration.

I am looking for any way to reduce the noise without too dearly compromising the system. I would also, for cost reasons, like to first try methods that did not involve the addition of new vents. Given that there is only a single 12" duct currently, I imagine there is little room for a bend of any sort. I was wondering if any sort of baffle might be appropriate.

Also, as the filters are in need of change - would any specific types of filters help with noise reduction.

I am sure it is evident that I do not really understand much of what I am asking about. I would appreciate any thoughts. Thanks.