The LD-18 digital water leak detector from SubSurface Locators reduces ambient, intermittent noises from dogs barking, cars passing by, footsteps and people talking. Its digital electronics sample the sounds every few thousandths of a second, and if it detects an intermittent sound, it suppresses it instantly. Water leak sounds are almost always continuous noises, and the unit can identify continuous leak sounds, even in difficult conditions like busy streets. 775-298-2701; www.subsurfaceleak.com.