Biology

The main roles of those interested in the biology aspect of the project were to select, extract, and analyse dolphin whistles. This involved using RavenLite, PAMGuard, and ARTwarp

Ultimately, analysis of whistles in this way will aid the conservation of dolphins, and allow researchers to learn more about the geographic differences in dolphin whistle types. See the ‘Home’ page for more information on our aims and goals.

Raven

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.

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.

PAMGuard

Once individual whistle .wav file clips are extracted from Raven, they can be traced and analysed in another computer programme called PAMGuard.

PAMGuard is a computer program used to measure and classify sounds produced by dolphins. In this project, we use PAMGuard to trace and measure dolphin whistles (Figure 2). Tracing whistles gives us lots of information about them, such as their lengths and frequency ranges. This information is often used in research on marine mammal behaviour, abundance, and distribution.

Within PAMguard, we use the ROCCA module. ROCCA stands for ‘Real-time Odontocete Call Classification Algorithm’. ROCCA is what allows us to trace and analyse whistles. This helps us understand the behaviour and geographical distribution of dolphins. So, both PAMGuard and RavenLite are important for the project, as well as more broad marine mammal research and conservation.

Figure 2: The left image shows the user interface of PAMGuard, with a spectrogram of an individual .wav clip extracted from Raven. Drawing a box around the whistle on the spectrogram opens a pop-up window shown in the image on the right. This allows the whistle to be manually traced by picking points along the whistle contour. The traced whistle is shown by the yellow line.