Dolphin Air Sac Motion Measurements During Vocalization by Two Noninvasive Ultrasonic Methods

Abstract

Method one uses short pulses of 2 MHz sound in a sonar system. A probe on the subject’s head projects impulses downward or inward. Echoes from successively deeper structures return to the probe to brighten a downward moving spot on a cathod ray tube. The spot jumps back to the top of the display and moves slightly to the right for the next pulse. Traced from left to right (Fig. 1) is the time pattern of movement of a line of internal reflecting structures, all correctly laid out in relative depth within the animal. Instead of being held stationary, the probe can be angulated on a small waterfilled balloon (flexible coupling) to outline internal structures (form image) and thus achieve the desired aim for time recording.