Sound transmission in the porpoise head

By using small hydrophones implanted in porpoise tissue and an external sound source, pulsed sound was found to be channeled by the blubber coat and strongly reflected by blubber‐muscle interfaces. Implants in the head showed concentration of sound in the proposed sound channel of the throat and jaws, complete acoustic isolation in the peribullary air space, and sound focusing in the melon. Sound‐velocity measurements in the melon showed a low‐velocity core extending from just below the anterior surface toward the right nasal plug and a graded outer shell of high‐velocity tissue. Such structure should beam sound generated or transmitted from the area of the superior narial passages forward and impedance match it closely to the surrounding water.