Development of direct acoustic energy flow analysis (DAEFA) for ship cabin noise in the medium-to-high frequency range

Noise analysis from heating, ventilation and air conditioning (HVAC) elements in ship cabins is needed to satisfy the strict noise regulation for the ship cabin, and it is very important for their effects to be evaluated in the early stage of design. In this paper, a direct acoustic energy flow analysis (DAEFA) model is presented for the noise analysis of the ship cabin to reflect direct fields of the sources from an HVAC element. Total acoustic fields are considered by deriving the fundamental solution of the energy flow model for direct and reverberant fields in a closed space. Sound propagation in the direct field is implemented using the geometrical acoustics concept, and noise sources introduced into the reverberant sound fields are considered by using the relationship between direct fields and the closed space boundaries. For cabin noise analysis using DAEFA, interior boundaries of the cabin are discretized, and boundary integral formulations for each field are integrated. Noise analysis is performed for various cases with the DAEFA model to minimize cabin noise. The optimal design derived through the analysis was applied to an actual ship, and cabin noise measurement was conducted onboard the applied ship. Comparison of the analysis and measurement results confirms the effectiveness of the proposed design.