[C320-list] odd noise from house battery area

[Nat Antler]

Nat Antler, Natiki, #161 1994
A subtle but persistent frog-like gentle croaking noise recurring every 3-4 seconds was driving us crazy while overnight in the slip. It seemed the loudest around the house battery compartment under the starboard settee. Tried switching off everything I could but it continued... would stop for 10 seconds or so and then recur. Any ideas? Pretty sure it was not coming from outside.