Dolphins produce one type of sound called whistles, which they use to communicate. Whistles can be aurally and visually detected and extracted. To do this, the project uses a computer programme called Raven.

1. Raven

RavenLite is a free programme made by The Cornell Lab Center for Conservation Bioacoustics. Raven allows audio recordings (called .wav files) containing dolphin whistles to be displayed as spectrograms and waveforms.

Once a whistle is detected in a sound recording, it can be selected by drawing a box around it in RavenLite (Figure 1). This allows whistles to be extracted as short, individual .wav file clips, which can later be analysed in PAMGuard (see page 3).

Figure 1: User interface of Raven during whistle extraction. The blue boxes are drawn manually around whistles to select them. This allows whistles in underwater audio recordings to be extracted as individual .wav clips, which can then be analysed further in PAMGuard.