Impacts of anthropogenic sound on marine mammals

Andrew Fischer, University of Tasmania, Institute for Marine and Antarctic Studies
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This page first made public: Aug 23, 2019

Summary

Marine mammals rely on sound for their daily existence. Therefore, the introduction of anthropogenic noise in the marine environment can have a profound impact on their behavior. Listening to sounds in the ocean is not only important to understand marine mammals behaviour, but also how their behaviour may be influenced by the changing anthropogenic soundscape. In this activity you will use MATLAB to visualise marine mammals and anthropogenic sound with a spectrogram and answer a few questions regarding the the impacts anthropogenic noise on marine mammals.

Learning Goals

After completion of this exercise you will, 1) become familiar with the types of sounds in the marine environment, 2) use MATLAB to listen to and visualize sound with a spectrogram and 3) learn how to read a and interpret a spectrogram

Context for Use

This exercise is for introductory marine science/policy students. These students will need to be somewhat familiar with MATLAB and understand directory paths, reading files and variables. The activity is executed within a LiveScript and therefore can be used with students that have minimal MATLAB experience.

Description and Teaching Materials

The activity is implemented with a MATLAB LiveScript. The LiveScript includes links to websites from which data can be downloaded. However, the two sound files used in their activity are included in the the attached file. This LiveScript also include a link to a lecture in YouTube given by Dr. John Ryan (MBARI) and Dr. John Johnson (NPS). Have the students watch the lecture and then work through the activity. Working through the LiveScript with the students is helpful, if you have. class that is less technically/MATLAB inclined.
MATLAB Live script and .wav files (Zip Archive 16.2MB Sep18 19)

Teaching Notes and Tips

This activity is part of an introductory class, Environmental and Spatial Data Analysis. It can be completed in about 2-2.5 hours. This includes watching the lecture. This LiveScript essentially makes this activity fool-proof. However, there are always the student who are unable to set the director path in MATLAB and have problems accessing the files. I make sure to walk through this with them every time they open MATLAB.

Assessment

The assessment for this activity is as follows. Students create a spectrogram of the zodiac engine using the .wav file included in this activity. They should have already created the orca spectrogram as part of the class activity. They hand in the following

1) Two spectrograms, one of the orca call and one of the zodiac motor. Make sure that you provide captions for each figure.

2) A brief description of the approximate frequencies and amplitudes of both sounds. They can create boxplots to help with that.

3) A brief page on how anthropogenic noise may impact marine mammal communication. Include some measures you think are importnat to lessen the impact of noise on marine mammals. (HINT: You may want to do some research on the attenuation of sound in water) Make sure that you reference your work appropriately.

Students are graded on the accuracy of their spectrogram and the presentation of their plots. Are axes labeled? Is there a colorbar? Are the units on the axes correct? By creating the boxplot of frequency, they should be able to provide a number mean frequency of the ocean and zodiac sounds.

In the discussion they should provide some information regarding the frequencies and intensity of each sound and see if they overlap. In other words, is the noise from the zodiac motor louder than the communication call of the orca? Students should also consider attenuation of the sound in the water and discussion potential conservation measures to protect the behaviour of marine mammals

References and Resources

Lecture: The Ocean Soundscape is a Whalefest, https://www.youtube.com/watch?v=oWXj2fiv6yA

Reading: Ryan et al., (2016) New Passive Acoustic Monitoring in Monterey Bay National Marine Sanctuary. IEEE Xplore. DOI: 10.1109/OCEANS.2016.7761363