Abstract

A propeller is said to be singing when it generates noise in a very narrow band of frequencies or almost at discrete frequencies with a typical waxing and waning characteristic. The singing of propellers is a phenomenon of resonant vibrations of blades excited by eddy shedding. Causes of the singing of propellers of ships and characteristics of the noise produced are discussed with data from a case study. Five frequencies of singing were observed at 50 Hz, 152 Hz, 250 Hz, 340 Hz, and 458 Hz depending on the state of the propeller. Marine fouling has a profound influence both on the frequencies and noise levels of singing. Airborne noise produced by singing propellers has deleterious effects on human habitability and working efficiency and may even cause damage to hearing. Modifications to trailing edge and lead filled grooves on the propeller blades are two important remedial measures to eliminate singing of propellers.