The airborne path in shipboard noise control

Abstract

Reverberant noise in living and working spaces other than the machinery room is typically controlled by structure‐borne paths. However, as machinery vibration isolation and foundation damping techniques are perfected, airborne flanking paths discussed in this paper become increasingly important. In contrast to representative masonry walls, the finite extent of shipboard partitioning and bulkheads is an essential factor in determining transmission loss (TL). Consequently, structural damping is beneficial not only near coincidence, but also at higher frequencies. A second distinguishing feature of much shipboard partitioning is frame stiffening. This extends the beneficial effect of damping to frequencies below coincidence. Stiffening frames cause marked TL degradation below the TL of the underlying uniform plate, in spite of the latter's smaller mass. In conclusion, the concept that mass per unit area is the single most important factor in determining TL is not relevant to the shipboard situation.