A/C sound insulation?

[ARoss]

PO had a 16k btu a/c installed in* the aft hanging locker of my MT34. One air outlet into the salon. Probably not optimal. *

After it crashed, (probably early 90's installation) rather than trying to get it repaired I installed a new, bigger a/c unit last year (20k),* and ran additional ducts so that it could put more cold air* both in the aft cabin and forward. * It's great for cooling, but the Adm. complains about the additional noise, and* it's in our sleeping quarters.

I think if I install some sound-baffle insulation inside the locker it'll* help.* Any thoughts on soft foam vs rigid foam, or any other products that'll work?* I am thinking that I can "liquid-nail" it to the inside of the locker on the aft side and the door.

I* also plan to put some rubber insulation of some sort* between the shelf and the base of the unit, so any thoughts on that aspect will also be welcome.*

 

[Great Laker]

First you need to determine the source and nature of the noise. Is it airborn from the AC unit (motors/fans) or vibrations through the mounting structure to the boat or via air intake and exit ducts or all three? These are treated differently.*

Airborne noise can be absorbed with materials such as Owens Corning 703 Rigid Fiberglass Board or Thermofiber Safing Insulation mounted on the inside walls of the cabinet. Vibrations can be absorbed by mounting the AC on energy absorbing feet (cork with rubber on both sides commonly used for furnaces)*or adding mass under the unit. Air ducts can be lined with insulation and have multiple right angle turns to avoid straight runs into the cabin. If the fan noise is high you might operate the unit on the lowest setting.*

Hope this helps.