This is a very sensitive listening device with multiple sensors that with the right training you can narrow down a person with as little as a scraping sound. Depending on the sub straight everything sounds completely different, so you would need a lot of experience with it to know the difference between a drip of water and a finger tap. We can even hook up to a microphone and drop it down to listen to a specific area to understand further what is happening or to maintain communication with a possible subject.