Fig. 2. A comparison of nasal cavity pressure and hydrophone recording during clicking (A) and whistling (B) for white whale MUK. For this recording, the animal was stationed at a depth of 1 m in San Diego Bay. The upper trace in each part shows pressure rising in the nasal cavity before the animal produces sound. The trace in B illustrates nasal pressure in response to a 500 ms tone. In response to the tone, the whale whistles approximately 400 ms after the suprathreshold tone is presented. The rise in nasal cavity pressure begins approximately 200 ms after the onset of the tone (not shown). Soon (220 ms) after the pressure rise begins, the whistle is recorded. Whistling requires considerably more pressure than clicks of similar amplitude (see also Ridgway and Carder, 1988). Because the click train is longer in duration, the axes are different for the two recordings (A and B).
