Theory of Sound
Marine diesels create very high noise levels – often well over 100 decibels. Engines are always located close to the boat user, generally in engine spaces made from GRP, timber or steel. Engine noise is then amplified by bouncing around between the hard bulkheads and the steel of the actual engines. Noise contributes seriously to fatigue and seasickness, as well as spoiling life on board.
There are several ways of reducing engine noise. Adding weight and thickness to the bulkhead with an insulation layers is one way since it helps to reduce noise transmission. Reducing the hardness and altering the texture of the bulkhead surfaces is another since a softer bulkhead facing will absorb more noise and stop bouncing it around and possibly even amplifying it.
Just like double or triple glazing windows at home, it pays to construct the noise barrier using multiple layers of thin material rather than a one simple layer many times thicker.
If you cocoon the engine with noise insulation you can reduce airborne noise by 85% and transform the comfort for all on board. Remember structure borne noise and exhaust noise are separate subjects, and Halyard can help with both.
Insulation should be used on as much of the total surface of the engine room as possible. Cut around pumps, filters and electrical items, but don’t leave large areas of hard surface for noise to bounce off. (Fig 1)
Hatches and steps must fit neatly and should have a noise tight cushion such as our hatch tape. (Fig 2)
Bulkheads around the engine should go right down to the hull. Don’t leave openings where noise can leak forward – for instance under a cabin floor. Remember that fuel and water tanks absorb and amplify noise. If you can’t put a bulkhead in front of them, at least insulate the actual tank.