Tones Vowels and Telephones

Tones, Vowels and Telephones

In this experiment, you will analyze various common sounds. You will use a Microphone connected to a computer. Logger Pro will display the waveform of each sound, and will perform a Fast Fourier Transform (or FFT) of the waveform. The FFT tells you the amplitudes and frequencies of a collection of sine waves that, when added together, would sound the same as the original waveform. In the first part of the experiment, you will study the sound of a tuning fork which produces a tone composed mainly of a single frequency. Next, you will observe the production of overtones on a tuning fork. Overtones whose frequencies are multiples of the fundamental are called harmonic; other overtones are called inharmonic. You will also analyze the sound produced when you say two vowels. An FFT graph will reveal that your voice is composed of a large number of individual frequencies. In the last part of the experiment, you will be given a problem to solve. How does the telephone company know what numbers you dial? Do those tones that you hear when you press the buttons on the telephone contain some kind of code? You can solve this problem and crack the code using the Microphone, the FFT analysis, and a cell phone!

OBJECTIVES  Use a Microphone to analyze the frequency components of a tuning fork and your voice.  Record overtones produced with a tuning fork.  Examine how a touch-tone dialing works.

MATERIALS computer Vernier Microphone LabPro or Universal Lab Interface 2 tuning forks (one ~256 Hz) Logger Pro Cell phone

PROCEDURE Part I Pure Tone 1. Connect the Vernier Microphone to Channel 1 of the interface.

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2. Open the file “34 Tones Vowels Telephone” in the Physics with Computers folder. The display will include both a graph and an FFT. The vertical axis of the graph corresponds to the variation in air pressure; the units are arbitrary. 3. Gently strike the palm of your hand or a rubber mallet with a tuning fork and hold it near the Microphone. Click to begin data collection. The data should be sinusoidal, similar to the sample on the first page of this lab. If you strike the fork too hard, it will create overtones, or a blend of higher frequencies in addition to the main frequency. 4. Print the wave that you observe. Use the value of the tuning fork as a title (graph options). 5. Use the Examine function to determine an average value for the period. Record this value in your data table. What did you do? ______6. Calculate the frequency and record in the data table. How did you determine the frequency? ______7. As you move the mouse across the FFT graph, record the predominant frequency as displayed in the data table. It should be close to both the stamped value and the frequency you calculated above 8. Calculate the % difference between frequency value stamped on the tuning fork and the value calculated from the waveform (question 6, above). Use the stamped value in the denominator. Is this number within 10%? 9. Repeat with the second tuning fork. Print the graph and title it with the value of the tuning fork.

Part II Overtones on a Tuning Fork 10. In this step, you will make the 256 Hz tuning fork produce an overtone. This time, strike the tuning fork on a piece of wood. The sound should be different than in part 1. Describe the difference, if any, between this sound, and the sound made when the tuning fork was struck in Part 1. 11. Strike the tuning fork and hold it near the Microphone. Click to begin data collection. Your waveform should now be more irregular. When you get a good data run, PRINT your graph. 12. Compare the waveform and the FFT to the ones produced in Part I. How does the waveform compare with that of Part 1. Is there more than one frequency? How do you know? ______

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______

13. Use the Examine button, and move the mouse cursor across the FFT graph to determine the fundamental frequency and the first overtone. Record these values in the data table.

Part III FFT of Two Vowels 14. Hold the Microphone near your mouth, say the vowel “e” and hold it while you click the button. Print the graph and FFT graph. The title should be “vowel sounds – E”. 15. Repeat, only this time say “o”. Print this graph as well with vowel sounds – O” as the title. 16. Describe the difference in the frequency structure between the two vowels. Does one have a higher frequency than the other? If so which one? Does one have more overtones? If so, which one? ______-

Part IV Telephone Dialer Frequencies 14. In this part of the experiment, you will analyze the sound made by a telephone tone dialer. Most cell phones can be made to make this sound, by going to settings menu, and choosing sounds. 15. Go to the Experiment menu and turn on “Enable Triggering”. Set the sound level to be greater than 2.6 V. 16. Once you get the “touch tone” dial sounds, hold the cell phone near the Microphone, press the “1” button on the phone, then Click to begin data collection. Using the FFT display, record the two predominant frequencies for this sound. 17. Repeat Step 14 for numbers “2” through “9”.

DATA TABLE Part I Pure Tone

Tuning fork 1 Tuning fork 2 1. Frequency on tuning fork (Hz) 2. Period from waveform (s) 3. Frequency from waveform (Hz) 4. Frequency from FFT graph (Hz) % difference bet 1 and 3

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Part II Overtones on a Tuning Fork

Frequency stamped on tuning fork (Hz) Fundamental frequency (Hz) Overtone frequency (Hz)

Part IV Telephone Dialer Frequencies

Button 1 2 3 Low frequency (Hz) High frequency (Hz)

Button 4 5 6 Low frequency (Hz)

High frequency (Hz)

Button 7 8 9 Low frequency (Hz) High frequency (Hz)

Questions for Part 4 1. Examine the data for the tone dialer. What pattern do you observe?

2. Which frequency is higher, the row frequency or the column frequency?______3. What is the row frequency for the 4, 5, and 6 buttons?______4. What is the column frequency for the 2, 5, and 8 buttons? ______5. Summarize how the telephone company tells what numbers you press when using a touch tone phone.

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