DNV SILENT class

DNV SILENT is a class notation that certifies a ship’s underwater radiated noise against defined limit curves, sold in tiers for the ship’s purpose: SILENT-R for fisheries research, SILENT-F for fishing, SILENT-E for environmental work, SILENT-S for seismic survey, plus a general SILENT-A for acoustic comfort. Compliance is shown by measured sound pressure levels over a frequency range, dominated at low frequency by propeller cavitation and at mid frequency by machinery and gear tones. Designers meet it with low-cavitation propellers, resilient machinery mounts, and quieted auxiliaries. The notation supports marine-mammal protection and survey data quality.