News Finding: In other words, the dolphins whistled more, but with much less complexity.
Paper Finding: In addition to modifying the shape, dolphin whistles were also higher frequency during increased broadband and 2.5 kHz TOL ambient noise immediately prior to the call.
News Context: What they found was that the increases in vessel noises resulted in higher whistle frequencies with reductions in complexity. In other words, the dolphins whistled more, but with much less complexity. Analyzing the data, the researchers found that with background noise, the dolphins' typically complex whistles essentially flatlined.
Paper Context: The ambient noise environment could also affect vocal learning, as young animals exposed to elevated noise may hear adjusted calls from conspecifics . In addition to modifying the shape, dolphin whistles were also higher frequency during increased broadband and 2.5 kHz TOL ambient noise immediately prior to the call. Increased low-frequency ambient noise may be causing dolphins to change their vocalization behaviour to avoid or compensate for masking.