Every morning when I step into my shower, I hear a lovely tapping sound that appears to be coming from beneath the floor on the other side of the (small) bathroom. The tapping sounds like a pipe may ave a slow leak in the somewhere in the floor. The tapping does not happen when the shower is off.

Is there a tool that can help me search/pin point the possible wall moisture before I dig into the wall? If so, where might I find it, and what can I expect to pay?