as the wall street journal, reports , after a spill in 2000, the [minerals management service] issued a safety notice saying that such a back-up device is "an essential component of a deepwater drilling system." the industry pushed back in 2001, citing alleged doubts about the capacity of this type of system to provide a reliable emergency backup. by 2003, government regulators decided that the matter needed more study after commissioning a report that offered another, more honest reason: "acoustic systems are not recommended because they tend to be very costly." i guess that depends on what they're compared to.the system costs about $500,000 per rig. bp is spending at least $5 million per day battling the spill, the well destroyed by the explosion is valued at $560 million, and estimated damages to fishing, tourism, and the environment already run into the billions.