Electronics technician Mike Williams told a federal government hearing in Kenner that the general safety alarm had been routinely placed on an "inhibited" setting in order to limit the number of noisy alerts.
"They did not want people woke up at 3 a.m. from false alarms," Williams told the panel.
The Washington Post said its review of federal enforcement records indicated other rig operators in the Gulf of Mexico routinely bypassed alarm systems and paid fines.
The alarm was one of a number of perceived shortcomings Williams testified about, The New York Times reported. Williams also recalled a balky computer system that routinely displayed nothing but a blue screen and a system to removed gases from the rig's drilling shack that had been in a bypass mode for five years.
The Times said Williams confirmed that the crew had nicknamed Deepwater Horizon "The well from hell" due to their worries about safety. He said the moniker was first coined by Stephen Curtis, one of the 11 crewmen killed in the April 20 explosion that sank the rig and unleashed an undersea gusher of crude oil.