Lesson Six: How does an animal’s environment affect the frequency of sound they use?

Introduction:

Animals use songs and sounds to communicate. Some of these sounds are produced within human auditory ranges, which for most of us is between 20 and 20,000 vibrations per second. (20 HZ-20kHZ) Sound that is lower than 20 vibrations is called infrasound. These are sounds that we cannot hear, but can be seen on a spectrogram. Thunderstorms and earthquakes produce sounds that are in the infrasound ranges. Elephants communicate with infrasound. This allows them to communicate with each other over very long distances. Some animals produce sounds that have more than 20,000 vibrations per second. These are called ultrasounds. Bats use ultrasound to communicate and find insects to eat. A bat will produce a high pitched squeak and the echoes of the ultrasound wave will bounce off of the insect indicating its position to a hungry bat. The human ear can recognize single sine waves because sounds with such a waveform sound "clean" or "clear" to humans; some sounds that approximate a pure sine wave are whistling, a crystal glass set to vibrate by running a wet finger around its rim, and the sound made by a tuning fork. To the human ear, a sound that is made up of more than one sine wave will either sound "noisy" or will have detectable harmonics; this may be described as a different timbre.

Learning Outcomes:

The learner will infer that vibrations are needed to make sound. They will demonstrate how low sounds have slower vibrations and high pitched sounds have faster vibrations.

Curriculum Alignment:

National Science Education Standards

Content Standard A: Abilities necessary to do scientific inquiry

• Understanding about scientific inquiry.
• Employ simple equipment and tools to gather data and extend the senses.

Content Standard B: Physical Science

• Position and motion of objects
• Sound is produced by vibrating objects. The pitch of the sound can be varied by changing the rate of vibration.

Content Standard C: Life Science

• The characteristics of organisms
• Organisms and their environments

Content Standard E: Science and Technology

• Abilities of technological design
• Understanding about science and technology
• Abilities to distinguish between natural objects and objects made by humans.

Content Standard F: Science in Personal and Social Perspectives

• Characteristics and changes in populations
• Changes in environments
• Science and technology in local challenges

Content Standard G: History and Nature of Science

• Science as a human endeavor

NC SCOS Music Curriculum

Goal 8: The learner will understand relationships between music, the other arts, and content areas outside the arts. (National Standard 8)

• 8.01 Identify similarities and differences in the meanings of common terms used in the other arts.
• 8.02 Identify ways in which the principles and subject matter of other content areas taught in the school are related to those of music.

Time:

60 minute period

Materials:

• Bat and elephant pictures and spectrograms
• Textbook
• Tape
• 30 cm long wood ruler

Technology Resources: Raven Lite

5E

Engage:

Show students a dog whistle. Blow the whistle and ask students what they know is special about dog ears? Discuss how dogs can hear things that we are unable to hear with our ears. Tell students that they will be investigating how to make sounds change.

Explore:

Give each student pair a ruler, tape and a text book. Ask students how we can make sounds with the ruler. Have students work in groups to develop strategies for making sound. If they are having difficulty, demonstrate for students how to place the ruler flat on the table, cover the end of the ruler with a book and pluck the end that is hanging off the table. The ruler will vibrate causing sound. Have students test different lengths of the ruler and listen to each sound. Students fill in data table about the sounds they produce and hear.

Example:

Length off table	Observations	Pitch
5 cm	Ruler is difficult to pluck, vibrate quickly	High
10cm
15cm
20cm	Ruler vibrates slowly	Low

Explain:

Discuss the data collected. The higher sounds were created when shorter ruler length was hanging off the table. The lower sounds were created when the longer ruler length was plucked. Discuss how we can hear the different pitches because our ears are sensitive to a certain range. Discuss how the dog whistle was not in our range. What does this tell us about animal hearing? Have students discuss how certain animals hear things that we cannot.

Elaborate:

Examine pictures of a bat and an elephant. Discuss what types of sounds and pitches they create. Ask students what we could use to detect sounds that were out of our range. Review the spectrograms that the students used in previous lessons. Ask students how spectrograms help us to see the sound. Show students two spectrograms (one bat, one elephant). Discuss the frequency of each animal. Students should infer that the bats have a higher frequency (ultrasound) and the elephants have a lower frequency (infrasound). Ask students how this is adapted to suit each animal’s environment.

Draw two sine waves (see diagram below) on the board without using the words and ask students what they notice about the lines? Accept all responses. Discuss how there are more peaks in the top picture and they are closer together. Discuss how the bottom line has the same height but that there are fewer and the distance between the peaks is longer. Discuss the lines as waves and do “the wave”

Compare the high and low frequencies of the bat and elephant to distance. Establish how lower frequencies travel farther than high frequencies. Allow students to demonstrate by striking soft tip mallets on their desk to replicate sounds/stomping of the elephant. Contrast the low sounds with the high frequency of small bells, finger cymbals or choir chimes. Also, explore how cultural instruments are created in their original habitat. Cultural communities choose materials due to their environment. Human and animal communicators alike utilize materials that produce sounds pleasing to the ear. A cockatoo uses a twig to beat on a log. If the cockatoo likes the sound of that twig it will save the twig. Many human musicians favor a particular instrument over another. A concert pianist will choose a grand piano over a console piano. Allow students to explore instrumentation from various international cultures.

Extend:

Use the Wild Music website to test your range of hearing. As we age our hearing is not quite as good so there may be sounds that your students can hear that you will not be able to hear.

Evaluate:

Science Notebook Data table

Vocabulary:

• Frequency - the number of waves produced per second which is the same as the number of vibrations produced per second
• Pitch – the highness or lowness of a tone, as determined by the frequency of vibrations per second.
• Infrasound - sound with a frequency too low to be heard by the human ear
• Ultrasound - acoustic energy in the form of waves having a frequency above the human hearing range

Websites:

• http://www.birds.cornell.edu/brp/elephant/ELPFAQ.html
• http://www.batdetective.com/sonograms.htm