The dolphin's search for food is aided by a form of sonar known as echolocation: it locates objects by producing sounds and listening for the echoes. A broadband burst pulse of clicking sounds is emitted in a focused beam in front of the dolphin. When the clicking sounds hit an object in the water, like a fish or rock, they bounce off and come back to the dolphin as echoes. Echolocation tells the dolphins the shape, size, speed, distance, and location of the object. To hear the returning echo, they have two small ear openings behind the eyes, but most sound waves are transmitted to the inner ear through the lower jaw. As the object of interest is approached, the echo becomes booming, and the dolphins adjust by decreasing the intensity of the emitted sounds. (This contrasts with bats and sonar, which reduce the sensitivity of the sound receptor.) The interclick interval also decreases as the animal nears the target. Evidently, the dolphin waits for each click's echo before clicking again. Echolocation details, such as signal strength, spectral qualities, and discrimination, are well understood by researchers. Bottlenose dolphins are also able to extract shape information, suggesting they are able to form an "echoic image" or sound picture of their targets.