Bioacoustics Lab- Spring 2013
BRING LAPTOP & HEADPHONES
Lab Preparation: Bring your Laptop to the class. If don´t have one you can use one of the COH´s
laptops for the duration of the Lab.
Before coming to the Lab: Download a copy of the free version of Raven Lite onto your laptop,
download only the “Software & Documentation”, for Mac or PC, from the Cornell Lab of Ornithology
website:
http://www.birds.cornell.edu/brp/raven/RavenVersions.html#RavenLite
After you download the program (RavenLite10_Executables) you will also have to register for a code to
use the program. You will register for the license by clicking on the link to the right of the Raven Lite
1.0 heading (“Get a free license). Fill out the form and an Email will be sent to you with the registration
code, use it and you’ll be ready to go.
Sound Files: Download the mystery sound file that you received by e-mail. If for some reason you did
not receive one by e-mail, your TA will give you one during class.
Objectives: The purpose of this lab is to describe (quantitatively and qualitatively) the diversity of
sounds produced by marine mammals, and use what you have learned about marine mammal
communication to relate to marine mammal behavior. All analysis will be conducted using the program
called Raven Lite 1.0. For each file, you will create a waveform and spectrogram for analysis. For each
species you will obtain a variety of measurements including the duration of a call, the peak frequency,
the frequency range, and any qualitative descriptions such as downward or upward frequency sweeps
(i.e. upward sweep from 1.5-2 kHz), harmonics, estimated number of animals vocalizing, etc. If there is
more than one animal vocalizing, you should also note the overall frequency range of that species’
sounds.
**In your report, you should print out or draw by hand at least one spectrogram in order to
illustrate a typical call and how your measurements were made. In addition, you may want to
save/print additional graphs or you can draw the sounds from the spectrograms by hand (make sure to
label appropriately) to remind you of what you were looking at.
To Begin: Double click on the Raven Lite icon. In the pinnipeds folder, open the file titled
“CAsealion_male.wav.” You will have an Oscillogram (or waveform) and a spectrogram, which
should look like the following:
Waveform:
Pressure
fluctuations
Time
Spectrogram:
Waveforms show pressure fluctuations from sound over time. Sound travels through air or
water as waves of high and low pressure. For example, when your stereo speaker vibrates - as the
speaker cone moves out, it pushes air molecules together (higher pressure), and then as it pulls away
from the compressed molecules there is a relative decrease in pressure. These pressure waves travel
away from the speaker towards your ear. The changes in pressure are what you hear as sound.
Relative, ambient (normal environmental) air or water pressure is usually “0” in the waveform. Louder
sounds will have much greater fluctuations in pressure (variations above and below 0) than quieter
sounds. (For the CA Sea Lion Male plot the ambient pressure level is 128 U). You can use the
waveform plot to determine where the sound is the ‘loudest’ in the call by finding the point were the
amplitude it the highest.
The command panel in Raven– Use the illustration below for working with both
waveform and spectrogram plots throughout the lab
To play the sound – click the
icon
Use to change the color pattern
of the spectrogram (color,
grayscale, etc.) This is VERY
useful when trying to visualize
the calls.
Playing commands
Show/Hide
Waveform
Hide Axes
Show/Hide
Spectrogram
Changes speed of
playback (↑ to hear
blue/fin whale
sounds). 0.5= half
speed, 1= real speed,
5= 5x fast, etc.)
Zoom in to
highlighted area
or zoom out. Very
useful for taking
measurements.
Play the sounds a few times and see if you can follow what you hear on the spectrogram
(sometimes changing the playback rate helps). In the spectrogram, frequency (Hz or kHz) or pitch is
shown on the Y-Axis and intensity or loudness of sound is shown with darker shading. Now take some
time to play around for a bit with some of the controls on the command panel (highlighting, filtering
and listening). Open the sounds of different species, make spectrograms, highlight various calls and
listen!
**See Tips/Suggestions later for suggestions of how to work with various sounds.
Once you feel comfortable using the Raven program, move on to making various
measurements on files in the “Files for analysis” folder. Use your cursor to carefully highlight the
calls both horizontally and vertically in the spectrogram. “Click and drag” in the spectrogram to
highlight the frequency range and length of the call you are interested in.
+
Time: 2.249 S Frequency: 8465 Hz
Power: 62.9 dB
Parameters to measure
To make measurements of what you’ve highlighted you will need to use your cursor. Place the
cursor in the spectrogram/waveform and see how the different parameters change. Place your cursor
at the highest point on the call to determine high frequency or the lowest point to determine low
frequency.
By moving your cursor in the spectrogram and waveform windows, you will be able to
measure different parameters: Time (s or ms), Frequency (Hz or kHz), and Power (dB) of the sounds
you are analyzing. Power is the amount of energy in the sound. To get peak frequency find the
highest power and determine where that is along the frequency scale.
Use the attached data sheet to make your sound measurements: In some of the sound files there
will be multiple signals. Just pick one or more and highlight the horizontal and vertical edges of it
carefully. Using your cursor determine: ∆ Time (call duration); High Frequency; Low Frequency;
Peak Frequency and Power at Peak Freq.
 For some files, you can also count the number of harmonics.
 Be careful not to confuse High frequency, which is the Highest “pitch” of the call, with Peak
Frequency- which is the most intense or loudest frequency of the call.
 For the ∆ Frequency measurement, record the range of frequencies used by the species for all
signals shown in the file.
 Carefully note the units (Hz or kHz, s or ms) as these will change between files.
 Use the comments column to add any qualitative information you think is relevant (i.e.
downward sweeps, pulse sound, many/few animals, etc.).
Tips:
 Changing the playback rate (speed) can help you hear features of sounds like pulsing (slowing
down rapidly pulsed sounds). Try slowing down some of the odontocete sounds. Increase the
rate of playback of the blue and fin whale sounds to hear them. Some files are already set at a
faster play rate. Watch as the cursor scrolls during playing to determine the speed.
Progressively make these sounds slower (and lower frequency) until you can no longer hear
them. In real time they are close to or outside of the low range of human hearing.
 For some files the calls are best visualized with the cool color scheme or standard gama color
scheme.
 Some files contain many animals calling simultaneously, such as the common dolphins. Try to
pick one or two whistles out to do your measurements.
 Use the zoom in feature to get a better image of individual calls and to take your
measurements.
Lab Report:
The lab will not follow the standard scientific paper format (Introduction, Methods, Results, etc) but
rather a more standard essay format that will emphasize your understanding of the acoustic ecology of
marine mammals. The purpose of this lab is to determine the marine mammal that produced your
mystery sound, describe the various acoustic components of the signal, and then discuss how this
sound relates to their social systems, group behavior, or habitat. This lab will require you to focus on a
specific species, and discuss what is currently known about the biological significance of the mystery
sound they produce. Because this lab report requires you to review what is currently known about the
acoustic behavior of your species, the lab will emphasize more background research and focused
reading than previous lab reports, and will require at least 3 scientific sources.
Lab Report Format
Acoustic Identification: Describe the mystery sound descriptively and quantitatively. Include the
analysis program that you used to investigate your mystery sound, how you measured the data, and
what parameters were measured (peak freq, high freq, call duration, etc). If you were listening to
this sound for the very first time, how would you describe it to other researchers? What were the
measurements that you took that helped you identified the species? Include a spectrogram in this
section, and make sure to include axes and do not forget to include the proper units (e.g., Hz or kHz,
mS). End this section with your best guess as to what species produced your sound and the relevant
measurements that you took that helped you to identify it. (1-2 paragraphs)
Sound Production: How is the sound produced (larynx, nasal passage, etc)? Who produces the
sound (males, females, pups)? During what time of the year is the sound produced (during the
breeding season, year round)? Where is it produced (in air or underwater)? This section will require
you to do a bit of background reading, and should demonstrate your understanding of how, when,
and where your species produces its mystery sound. (1-2 paragraphs)
Biological Significance/Function: What is currently known about the primary purpose of the sound?
Is it used during social contexts, and if so, which ones? Who is the sound intended for? Depending on
the sound you were assigned, you may find that there is either a lot of information (signature whistles)
or very little (some manatee sounds) available. If you find very little information, state that, and
include some ideas as to why you believe it is difficult to study the communication and behavior of
your marine mammal. Again, this section will require you to do some background reading using
scientific references. (2-3 paragraphs)
Relationship to Habitat/Environment: Describe the typical habitat that your animal can be found in,
and discuss why this signal might be effective in this type of environment. Discuss again whether
this sound is produced in air and underwater, and note why the acoustic characteristics of that signal
would be well designed for that medium. Include references. (1-2 paragraphs)
Conclusion: End with a concluding paragraph, discussing in general why sound is so important for
your species. Including possible future research directions based on what is still unknown about your
species communication system. (1 paragraph)