When you first turn the ignition on, the fuel pump briefly runs to pressurize the system. That is a mechanical sound. If the pump runs more than a second or two, and you hear gurgling or other noises, odds are you have a leak in the fuel system. It's not just the lines that may develop a hole, but there have also been problems with the fuel filter housing a few years back. As Twolane recommended, open the gas cap and listen closely as you turn the ignition on. If you get something other than a very brief whirring noise from the pump, it's time to open things up and take a good look at everything from the pump to the filter and housing to the lines.
JMHO - Jerry