The LD-18 digital water leak detector from SubSurface Leak Detection is designed to significantly reduce ambient, intermittent noises from dogs barking, cars passing by, footsteps and people talking. The 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 these continuous leak sounds even in difficult conditions, like busy streets. It is not necessary for the user to listen with the headphones if the unit hears the leak sounds on the asphalt or the ground directly over the pipe. 408/249-4673; www.subsurfaceleak.com.