Sound Proofing a container whilst facilitating good air supply.

Gosh, all I can do is guess, but a long insulated duct for both intact and one for the exhaust. The duct should be folded with sound deadening material lining the inside.

Environmentally, that idea would be a mess to maintain, but it would work.

I agree, this actionshould definitely reduce the sound levels, but the directional flow changes (which would likely be several) could make pressure drop an issue.

Can marine acoustic foam sheets be put to use? It can be cut and carved to shape in order to fit the engine compartment of any boat, and is simply attached to the engine compartment surfaces using an adhesive.

Many years ago the top half of a room with air-driven can-inversion equipment became lined with this stuff, achieving a 7dB reduction in ambient noise, which was sufficient in this case to enable operatives to use the machine without ear defenders while in compliance with Health & Safety best practice.

Can you "move" the radiator outside the engine compartment? That is, can you separate the engine from the radiator by placing sound-deadening board between them and allow free air to be blown over the radiator, or is its noise at a high level also?

Another possible solution is to use a water-cooled radiator, but that requires either a large, open water tank that has enough surface area to maintain a low enough temperature to cool itself by evaporation, or the use of an evaporative cooler with more fans and water spray, both with make-up water, or requires that the cooling water be wasted.

Have you tried staggered baffles? -_-_-_-_-_ sort of thing in some reasonably sound deadening material (think ductboard or something like that).

How about dual isolation. You know, an outer containment and inner containment type configuration. Or, a box within a box, one might say.

Design the air in and air out openings as labyrinth type seals and cover all the sound reflecting surfaces within the engine compartment and the labyrinth seals with the marine soundproofing material described in another post. That will more than do it.

There are quite a few options available to you. One is to use a horizontally mounted radiator on the roof of the shipping container with an electric fan mounted under, blowing vertically upwards. This is the most efficient arrangement for the radiator cooling system. If you then put the combustion air inlet just outside the container also, the airflow through for cooling is reduced to about one third of the current setup. This will make the noise attenuators to the container much simpler.

the next way, if you happen to be near a stream, is to mount a marine heat exchanger on the outside or inside. Use the existing fresh water circulating pump to circulate the engine coolant through the heat exchanger and a remote pump to circulate the stream (raw) water through the inside of the tubes of the heat exchanger.

Yet another way is to leave the machinery as is and arrange splitter boxes (air attenuators) both ends of the container. This achieves a more effective cooling air path, along the full length of the container. Cross flow is nowhere as good and usually ends up with very hot spots inside. Using 90 degree curved sections facing vertically upwards on the discharge end, downwards on the inlet end, often help also.

In all instances, the exhaust manifold, exhaust pipe and silencer need to be lagged and as much as possible mounted in its own enclosure on the roof of the container (again to minimize heat inside, thus enabling a smaller air flow, hence maximum noise attenuation)

Remember though that a diesel engine is only about 30% efficient, so a say 100kW set, has to get rid of about 100kW of radiated heat as well as 100kW of exhaust heat and 100kW of useful electrical output. I mention 100kW as I do not know the size of your set, but the same ratios apply.

Don't be tempted to use really cheap soundproofing materials, they usually burn well. Or if you do, then let us know and we can give you some tips on fire fighting systems.

Look up any manufacturer of stationary gen-sets and look at their enclosures.

My Kholer has one and the loudest part is the exhaust which I ducted outside with an additional muffler. You cannot hear it from the house 50 feet away.

Lets look at the individual sources of noise, quantify them then deal with them in order of size. The biggest noise has to be the exhaust or there is something very wrong. So get the exhaust away from the cabinet and make sure it's properly silenced. My experience of static gear and auxiliary power units is that they can be far below the standard of silencing many car manufacturers have to achieve. Nw there's the fan noise you mention and radiated noise from the surfaces of the engine and it's ancilliaries. If it's a diesel you'll probably have quite a bit if combustion noise, so I'd see if the engine surfaces can be surronded or insulated without affecting the cooling.Try to identify sources and frequencies, then solutions can be tailored.

Fan design can have a big effect on the noise emitted. Make sure the fan blades are irregularly spaced rotationally not evenly spaced.