Fig. 5. On a cue, the whale dived from the surface (A) to the hearing test platform (HTP) and stationed (B) to listen for tones from the projector 2 m below the HTP. The whale responded to a series of tones projected at random intervals (see Fig. 3) until the trainer signaled the end of the test dive by sounding a frequency-swept bridge tone (BSt). On hearing the BSt, the whale returned to the surface (C) for a fish reward.