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A ceiling of this type, combining mass, decoupling, resilient mounts and insulation is capable of attenuating noise 60-75 dB over 1000-5000 Hz.<ref>The Green Glue Company, http://www.greengluecompany.com</ref>
Similar techniques could be used on the bulkheads where feasible. Consider alternate arrangements to simplify construction. For example, in the engine room use a viscoelastic glue to stick a non-combustible panel on the bulkhead, then attach the composite insulation. In the living space on the other side attach furring strips using neoprene rubber. If more isolation is needed incorporate rubber mat or more insulation. Always leave an air gap to prevent acoustical conduction.
If there is ductwork originating in the engine room, use round lined ductwork (insulated on the inside). Round ducts transfer less sound than square ones. In the engine room coat the exterior of the duct with a viscoelastic material, and cover it with a soffit to prevent exposure to direct sound. Consider a 90 or 180 degree bend to force sound to interact with the duct liner. Where possible, use serpentine lengths of lined flex duct to create a more complex path for sound.
