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Fans and their associated ventilation ducts are amongst the major sources of airborne noise encountered within a submarine. Health & Safety Standards require that the ship's crew are not exposed to unnecessary high levels of noise and have a suitable environment free from intrusive noise in order to work and rest. The problem with noise emitted from fans and ducts in submarines can be categorised as follows:
a) In machinery spaces where there is a significant population of fans, for recirculation and cooling purposes, their combined contribution is significant compared with the total airborne noise level due to all machinery sources in such compartments.
b) Noise can be transmitted via supply and exhaust ventilation ducts from noisy fan plenums to quiet compartments elsewhere in the boat.
c) Due to necessary space constraints within a submarine, a fan plenum can be situated adjacent to a quiet compartment, and hence airborne noise transmitted via common structural boundaries then becomes significant.
Using selected case studies this paper shows how one can determine the airborne noise contribution of fans and ventilation ducts in submarines, and the appropriate acoustic treatments that may be necessary, through the use of computer-based predictive models.