For a water leak a sound imaging device is not going to help you.
You should definitely try a thermal camera. Any moisture will create small temperature differences which are easily picked up by a thermal camera.
You should definitely try a thermal camera. Any moisture will create small temperature differences which are easily picked up by a thermal camera.
A leak only turns invisible if the water has the exact same temperature as the wall and there is no meaningful evaporation happening (as that cools the affected area).
Of course don't let me stop you from actively probing your all using RF. Though also there you might have good chances with IR, since wet $stuff should behave differently than dry $stuff ;-)