International harmonization of procedures for measuring and analyzing of vessel underwater radiated noise

The habitat of the endangered southern resident killer whale (SRKW) overlaps major international shipping lanes near the Port of Vancouver, British Columbia. Shipping is a dominant source of underwater noise, which can hinder SRKW key life functions. To reduce environmental pressure on the SRKWs, Vancouver Fraser Port Authority offers incentives for quieter ships. However, the absence of a widely accepted underwater radiated noise (URN) measurement procedure hinders the determination of relative quietness. We review URN measurement procedures, summarizing results to date from two Canadian-led projects aimed at improving harmonization of shallow-water URN measurement procedures: One supports the International Organization for Standardization (ISO) in the development of a URN measurement standard; the other supports the alignment of URN measurement procedures developed by ship classification societies. Weaknesses in conventional shallow-water URN metrics are identified, and two alternative metrics proposed. Optimal shallow-water measurement geometry is identified. •Numerical experiments help optimize geometry for measuring vessel underwater radiated noise (URN) in shallow water.•Recommended receiver location is at the seabed, at ranges up to 4 water depths.•The URN metric source level exhibits undesirable dependence on one's choice of nominal source depth.•The URN metric radiated noise level exhibits undesirable dependence on the measurement geometry.•An adjusted source level and adjusted radiated noise level are proposed to address the weaknesses in the conventional source level and radiated noise level.