Introduction: The Sound Wave Analysis experiment is a discovery-based activity. Students will develop an understanding of sound wave properties: frequency, period and amplitude, and observe the beat frequency between two similar frequencies.

This activity is modeled after Vernier: Sounds, Waves and Beats experiment: http://www.vernier.com/

Timing: This activity should take about 60-90 minutes to complete.

Group Size: Small groups (3 or 4)

Learning Objectives: The objective of this lab/activity is to:

a) Introduce the following key concepts:

-Sound waveforms

-The relationship between pitch and frequency

-The relationship between amplitude and loudness

-Beat frequency

b) Reinforce the following concepts from the previous lab work:

-Frequency

-Period

-Amplitude

Guiding Question: What is a pure note and what does its waveform look like?

Materials: This lab requires the use of a microphone and wave analyzer for each group. The instructions provided are based on the use of Vernier: Labpro or Labquest, a Motion detector, and the Logger Pro software.

Labpro -

Most of this equipment can be found in any modern Physics classroom. There are also less expensive options through Vernier. Their Logger lite or Go Pro setups are capable of running this activity and will not cost as much. Other companies have similar probes. The Pasco probes seem capable, but I have not had much experience with them.

Photocopy enough activity sheets for each student.

Procedures:

Students should read the opening discussion as a group and highlight the important points. Take a moment to answer any general questions before starting the experiment. The procedure is relatively straight forward. Connection issues may arise with the probe. Make sure students have plugged the microphone into the correct port. The waveform should be sinusoidal, if there is any roughness, have the students redo the trial. Students will need to analyze the graph for the time taken between successive crests. As the stylus passes over the wave, it should give amplitude and time readings.

The beat frequency is probably the most difficult to visualize. When two notes are sounded at once, the interference pattern will look like a wave within a wave. Look for the variations in amplitude…. It almost looks like pulses, or the body of a caterpillar. Students will also need to analyze this graph for the time taken between successive crests (or bulges).

Sound Wave Analysis is a collaborative learning activity. To succeed, students will need to work together and use their time wisely.

Note: Sound waves are actually longitudinal, but the program shows them as transverse for ease of viewing.

Assessment: Much of students grade will be determined by their calculated results for frequency and how they compare to the known frequencies of the tuning forks. They will also be assessed on their closure question answers.

1) Compare the known values of frequency (written on tuning fork) to the calculated value of frequency for each tuning fork by using percent error.

Answers will vary depending on results. Fewer than 5% error would be appropriate for this activity.

2) How does changing the amplitude of the waveform affect the sound we hear?

Increasing and decreasing amplitude, increases or decrease the loudness of sound we hear.

3) How does changing the frequency of the waveform affect the sound we hear?

Increasing and decreasing frequency, increases or decrease the pitch of sound we hear.

4) How would increasing the frequency of the tuning fork affect the waveform?

Increasing and decreasing frequency would either, bunch the waveform or spread it out.

5) Does the beat frequency correspond to any other data you have collected? Look carefully; you might be surprised at the pattern at the pattern you find.

It is the same as the difference in frequencies of the tuning forks.

6) How do you think musicians use beat frequency to tune their instruments?

Varying answers, but it could be… They try to eliminate the rising and falling loudness (beats) until it is one clear tone.

Resources:

GoMotion (cheaper option for motion detector) - ?

General use of Vernier sensors -

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