Lesson Plan

Acoustics 1: The World of Underwater Sound

Harbor porpoise in Glacier Bay

The underwater world of Glacier Bay is filled with amazing sounds.

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Grade Level:
Sixth Grade-Eighth Grade
Subject:
Biology: Animals, Marine Biology, Oceanography, Oceans, Science and Technology, Wildlife Biology
Duration:
One Class Period (50 min)
Group Size:
Up to 36
Setting:
classroom
National/State Standards:
NS.5-8.1 Science as Inquiry
NS.5-8.3 Life Science
NS.5-8.7 History and Nature of Science
Keywords:
marine mammals, underwater, ocean, acoustics, humpback whales, orca, alaska, marine biology, sound, Hearing, water

Overview

Students begin this investigation by watching the seven-minute video, "Underwater Acoustic Monitoring." Students discuss their reactions to the video and then listen to sound clips of ocean animals and human-made sounds. This will familiarize them with sounds commonly heard in the ocean. This investigation demonstrates how humans and marine mammals rely on sound for communication and even survival.

Objective(s)

Focus Questions:

  1. What is underwater acoustic monitoring?
  2. What sounds can you hear underwater?
  3. Why is underwater acoustic monitoring important?
  4. How is sound important to marine mammal survival? 

Background

Our "Underwater Acoustics" curricula unit is divided into three lesson plans, each taking one class session to complete. They are part of our "Middle School Scientists" series that explore the fascinating research and resources of Glacier Bay National Park.

Check out the other lessons:

Acoustics 1: The World of Underwater Sound
Acoustics 2: Echolocation in Action
Acoustics 3: On the Trail of a Whale


Sound travels in waves. Waves are rhythmic disturbances that carry energy through space, like water ripples traveling across a pond's surface. Sound waves can travel through different solids, liquids, and gases. The study of sound is called acoustics and researchers in Glacier Bay conduct underwater acoustic monitoring. 

The ocean is full of sound, some natural and some anthropogenic (human-made). Most anthropogenic sound comes from boat traffic, especially large shipping freighters. Other human noise contributors come from industrial activities such as drilling, mining and militaryobservations using sonar. In Glacier Bay, most boat noise is produced by small recreational boats, cruise ships, and tour boats. Other natural sounds you can hear underwater include, surf, rain, wind, underwater earthquakes, glaciers calving, fish, crustaceans, marine mammals, and more! These underwater sounds are heard and recorded by a hydrophone. Many marine animals, especially mammals, rely on sound to communicate, navigate, find food, and interact with their environment. By studying underwater sound and analyzing data, scientists are trying to understand how ambient noise, or background noise, may impact or alter the behavior of marine mammals and other ocean animals. 

Your ears allow you to hear sounds because they are caused by the vibration of objects. For example, your voice is produced by the vibrations of your vocal chords. The energy produced by these vibrations is carried to your friend's ears by sound waves. Loud sounds have more energy than soft sounds. The volume (or loudness) of a sound is measured in decibels (dB). The rustling of leaves measures about 15 dB while a jet plane taking off measures about 150 dB. 

Wave frequency determines the pitch of a sound. Pitch is defined as the highness or lowness of a sound. The pitch you hear depends on the sound waves' frequency, how quickly the sound waves complete a wave. The higher the frequency, the higher the pitch, and the lower the frequency, the lower the pitch. Pitch or frequency is measured in cycles per second, or Hertz (Hz). For example, most people can hear frequencies from between 20 Hz to 20,000 Hz. Sound frequencies over 20,000 Hz are called ultrasonic waves and are out of our range of hearing. A dog whistle frequency is optimized to produce sounds above 20,000 Hz, which is inaudible to the human ear. 

High frequency sounds do not travel very far in water because their wavelengths are short and the energy gets rapidly absorbed by water. Low frequency sound waves travel farther in water because of their longer wavelengths. Humpback whales produce sounds that are within the range of human hearing. Their songs can travel 20-30 kilometers or more. A blue whale produces infrasonic sound, which is well below our range of hearing. These low frequency waves can travel thousands of kilometers in water.   

Materials

Materials Needed · 

Procedure

Assessment

Underwater Acoustics Assessment

The following pre and post-tests provide assessment for material covered by the entire Underwater Acoustics Curriculum series (Lessons 1-3)

Extensions

Extensions:

"Try Listening For Yourself" activity.
This link provides three audio clips of humpback whale vocalizations that will allow students to compare pitch and frequency. The site also provides in depth information on humpback whale song. Students can also link to this site and conduct this activity at home.
http://www.learner.org/jnorth/tm/hwhale/SingingHumpback.html 

"Soundscape Constructor" activity.
This link will allow students to construct their own soundscape by choosing their favorite sounds. http://www.exploratorium.edu/listen/activities/soundscapes/deploy/SoundscapeConstructor.swf 

Play additional sound clips of natural or human-made sounds heard in the ocean. Choose five clips from the list below that reflect a variety of sounds. Draw five columns on the board and write each sound at the top of each column. As you play the clips, have students write down what emotions they associate with each sound on sticky notes. When the listening activity is complete, have them place their sticky notes in the appropriate columns. Discuss the emotions they associated with the various sounds. In their journals, have students reflect on how this noise might affect marine mammals.

Vessel Noise

Cruise Ship
Freighter
State Ferry
Small Diesel Engine
Outboard Engine (60 hp) at 20 knots
Outboard Engine (60 hp) at 10 knots
Mid-sized Vessel
Propeller Whine

Ambient Noise

 

Heavy Rain
Light Rain
Snowfall
Light Winds
Moderate Winds
Wind with Ship Noise

 

Additional Resources

References/Resources:

http://www.nps.gov/glba/naturescience/acoustics.htm
Official Glacier Bay National Park website. Acoustic monitoring research. 

http://www.dosits.org/audio/marinemammals/
Discovery of Sound in the Sea Audio Gallery. 

http://www.dosits.org/
This website will introduce you the science and uses of "Sound in the Sea." 

http://oceanlink.info/index.html
Marine biology education. 

http://oceanlink.info/oinfo/acoustics/acoustics.html
The Bamfield Marine Sciences Centre also has lots of information on underwater acoustics and recordings at

Vocabulary

acoustics, ambient noise, anthropogenic, decibel, frequency, hydrophone, infrasonic, pitch, ultrasonic