Experiment 12

Experiment 12 PROPERTIES OF SOUND

PROCEDURE

1. Open up the Microphone Workbook and fill in the header information.

2. The microphone should be connected to the DataLogger interface box, and the box plugged in. Open up the Tones application.

3. Touch the Collect button on the graph, and whistle or make some other noise into the microphone. You should observe a waveform being plotted. If that is the case, hit the Stop button. If this does not seem to work, consult the lab instructor.

Pure Tones: 4. Sound the tuning fork by gently striking it against a soft surface, or by twanging it with thumb and forefinger. Hold it up close to the microphone until you observe a uniform trace. Hit the Collect button. As one partner produces the tone, the other should hit the Collect button in the LoggerPro window. If no waveform is traced, move the microphone a little closer to the source.

5. Hit the Stop button and use the ANALYZE...Examine menu to determine the maximum and minimum excursions of the pressure in the wave. The units on the plot are arbitrary, but can be converted to N/m²through a calibration process that is not needed here. A cross-hair cursor will appear and the graphical coordinates of any point on the plot will be displayed. Record the maximum and minimum values in cells B15:C15 on the Worksheet.

6. With the mouse select from 5 to 10 cycles of oscillation. Under the VIEW menu, select Zoom In. The graph will zoom in on this part of the plot. Record the time (horizontal) coordinates at the left-most peak and at the right-most peak. Enter these values in cells D15:E15. Enter the number of cycles spanned in cell F15. Select VIEW...Undo Zoom to return to the original trace.

7. Select the FFT Graph to view the frequency spectrum of the sound. Locate the fundamental peak in the spectrum with the cursor, and record the average value of the peak frequency range in cell B19. Also record the frequencies of any other significant peaks that you observe in cells C19:E19.

Complex Sounds: 8. Go back to the real time window and hit the Collect button. Sound the bell by ringing it gently. Repeat until you obtain a fairly uniform waveform.

9. Perform the same measurements as before of the maximum and minimum excursions of the wave. Record the values in cells B38:C38. Repeat the zoom-in and measure the time coordinates at the ends of the waveform. Record the time values in cells D38:E38, and the number of cycles in cell F38.

10. Switch over to the FFT Graph and measure the average peak frequency of the fundamental. Record the value in cell B42. Also record the frequencies of any other significant peaks that you observe in cells C42:E42.

Human Voice:

11. Go back to the real time window and hit the Collect button. Sound the tuning fork and listen to the tone. Then one partner (the best singer) should sing at that pitch and try different vowel sounds. Look at the waveforms for

(long vowels); and ah, eh, ih, (short vowels) etc., and find the one that appears the most sinusoidal. Measure the period as before. Record this vowel in cell E52, the time values in cells B56:C56, and the number of cycles in cell D56 on the Worksheet.

12. Switch over to the FFT Graph and measure the average peak frequency of the fundamental. Record the value in cell B60. Also record the frequencies of any other significant peaks that you observe in cells C60:E60.

13. In the real time window, hit the Collect button. One partner should speak into the microphone the sound of the vowel (long) . Hit the Stop button. The real time plot looks fairly complex. Repeat the zoom-in and measure the time coordinates at the ends of the waveform. Record the time values in cells B64:C64, and the number of cycles in cell D64.

14. The FFTGraph can be used to reveal some information about the sound that was made. The major band of frequencies at which your vocal tract resonates is called the formant of this particular sound. Use the ANALYZE...Examine to determine the peak frequency or frequencies of this vowel, along with the approximate range of frequencies that it covers. Record these values in cells B82:C82. Record the properties of any secondary peak frequencies that are present in cells D82:E82.

15. Under the EDIT menu, select COPY . Go to the Worksheet and PASTE the data in the space indicated, at cell B85.

16. Take the tube and pronounce the vowels into it so your partner can hear you. Determine which of the long vowels is most intelligible; which is least intelligible? Record these findings in cells D111 and D113.

17. As you pronounce the most intelligible vowel through the tube, hit the Collect button to obtain a full trace.

18. Under the EDIT menu, select COPY . Go to the Worksheet and PASTE the data in the space indicated, at cell B115.

19. Go back to the real time window and hit the Collect button. The other partner should now enunciate the consonant "s-s-s-s-s". (Don’t say "ess", but reproduce the way the letter sounds in a sentence). Use the FFTGraph to reveal some information about the sound that was made. Record your observations in response to Question 4 on the Worksheet.

20. Print out the Worksheet and use it to develop your lab report at home.