In humans, long or repeated exposure to sounds at or above 85 decibels can cause hearing loss.
K Venkataraman, director of ZSI in Kolkata, said, “The sonic waves from warships might have caused the stranding of the whales (in shallow waters).” He added that similar incidents had been reported from the Bahamas, where the US navy conducts its exercises.
Avijit Mitra, former head of the marine science department of Calcutta University, said, “Sonic waves from warships can burst the thin membranes of a whale’s swim bladder, which it uses to maintain buoyancy.”
The Andaman and Nicobar Command (ANC) — the unified command of the Indian armed forces and coast guard — however, was sceptical. “I am not sure if sonic waves have any effect on marine life,” said its spokesperson.
On October 22, fishermen found 40 dead pilot whales in Elizabeth Bay in Andaman.