# Too Cold to Chirp?

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#### Updated on Feb 06, 2012

Grade Level: 6th - 8th; Type: Life Science, Physical Science

### Objective:

This projects looks for a correlation between temperature and the intensity of cricket chirping.

The goal is to have the student formulate and test a hypothesis about the relationship between temperature and cricket metabolism.

• Does temperature affect the sound intensity of chirping produced by crickets?
• Can a mathematical relationship be obtained that described the relationship of temperature and the intensity of cricket chirping?
• Can similar relationships be predicted for other kinds of singing insects based on the results found for cricket chirping?

Choruses of cicadas, katydids, and crickets are a familiar sound during the warmer months of the year. Cicadas sing in late afternoon, while crickets start chirping at dusk. Late at night, katydids take up their songs, which continue until the early hours of the morning. The songs are all used for communication.

Male crickets and katydids make sounds with their wings. The singing of cicadas comes from the vibrating membranes on the sides of the abdomens of males.

Insects are cold-blooded, which means their metabolisms increase as temperature goes up. Crickets need a certain amount of energy to rub their wings together to produce chirping. At higher temperatures, the energy threshold is easily reached. At very low temperatures, less energy is available and the rate of chirping is slower.

Cricket chirps are produced when a cricket contracts the muscles in its wings, creating wing beats. Each wing beat produces many small vibrations. The vibrations determine the rate (number per unit time) and sound intensity (energy content) of the chirps. (Sound intensity is a quantitative measure of sound volume.)

In 1897, an American physicist by the name of Amos Dolbear published a paper in which he proposed a correlation between temperature and the rate at which the Snowy Tree Cricket chirps. He did not consider sound intensity.

Sound waves are introduced into the air by vibrations. The amount of energy that the cricket’s sound wave carries depends on the amplitudes of the vibrations produced by the wing beats. If more energy is put into rubbing the wings together, the vibrations increase in amplitude and the chirp acquires a higher sound intensity.

The scale that is used to express sound intensity is based on powers of 10. Known as the decibel scale, it assigns a level of 0 decibels to a sound intensity of 1x10-12 W/m2. A sound that is 10 times more intense is assigned a value of 10 dB, and a sound 100 times as intense is given a value of 20 dB. This means that if a sound is 10x times more intense than another sound, it has a decibel reading that is 10x higher than the less intense sound.

• Digital outdoor thermometer
• Flashlight
• Sound level meter

Materials can be found on the Internet.

1. Read about the effects of temperature on the metabolism of insects and formulate a hypothesis about the relationship between temperature and the sound intensity of the chirping of choruses of crickets.
2. Find a location from which you can listen to a chorus of crickets without disturbing them.
3. Measure the ambient temperature at that location.
4. Measure the sound intensity in decibels of the cricket chorus using a sound level meter.
5. Return to the monitoring location each evening for a month, and make the same measurements.
6. Tabulate and plot your sound intensity versus temperature data.

Convert the sound intensities in decibels to units of W/m2.

1. Look a mathematical relationship that summarizes any trends observed in the data.
2. Evaluate your hypothesis in light of your data. Revise it if necessary use it to predict temperature-intensity relationships for other singing insects.
 Date Temperature Sound intensity (dB) Sound intensity (W/m2)

Terms/Concepts: Cicadas; Katydids; Crickets; Metabolism; Temperature; Sound intensity; Decibels; Loudness; Sound waves; Amplitude; Vibrations

References:

Dr. Frost has been preparing curriculum materials for middle and high school students since 1995. After completing graduate work in materials science at the University of Virginia, he held a postdoctoral fellowship in chemistry at Stanford. He is the author of The Globalization of Trade, an introduction to the economics of globalization for young readers.