Close the hood latch on driver's side and lock the doors. Listen again after 4 minutes and see if the noise is gone. Until the network shuts off all modules you could have the TCM pulsing the STH solenoid. You really need to measure the current draw with an ammeter. You will have to fashion a way to...

You don't need to lock the doors for a drain test, just serial plug the multimeter to the battery, leave it on then wait 10 minutes. Pretty much everything shuts down - may want perhaps to remove the alarm siren fuse to be sure. Only my trunk lights refuse to go off at 10 min so I usually disconnect...