lab 12

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University of Notre Dame *

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2001

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Electrical Engineering

Date

Feb 20, 2024

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docx

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Laboratory 12 Report Exercise 1  What do your hands do to produce this sound? When your hands clap together, air particles travel through and create a wave. This occurs between the hands which causes the noise.  How does the sound reach your ears? The sound travels to your ears because the air between your hands goes out and the sound waves enter through the ear canal. Sketch pressure in the cylinder as a function of position along the cylinder axis for the figures (a) and (b) to the right. Experiment 1 (a)  Clap your hands together. What does the output look like? The output had many waves that were very sharp, but they disappeared very quickly  Make a continuous humming sound, for example "ahhhh". Adjust the scales until you are satisfied with the oscilloscope representation of the sound. (You can do this before or after you have frozen the live input. Describe some of the characteristics of the sound pattern. Does your humming sound wave have a definite frequency? How do you justify your answer? The sound pattern stays consistent throughout humming. When I hummed more loudly, the waves increased. The wave does not have a definite frequency because when I hummed louder the wave was not as consistent. (b)  Screen capture the pattern and paste it into your log. Describe the pattern. Does the tone generator producing a pure sine wave? How does the waveform of the tone-generator sound compare to the waveform of the humming sound?

The wave above has a frequency of 100 hertz. It is very consistent, and the waves are all around the same. This seems to be a pure sine wave. This wave is more spread out than the humming one was. The humming sound had more abrupt spikes. This one also stayed much more consistent.  Repeat the procedure (without screen capture) for different frequencies and compare the patterns. When decreasing the frequency, the waves become more spread out and not as high. (c)  Obtain a Fast Fourier Transform of a sine wave signal at 440 and 1000 Hz produced by the tone generator. Does it look like you would expect it to look? At 440 Hz signal had a higher audio level than the 1000 Hz. The 440 Hz also had a higher wavelength than the 1000 Hz frequency. This is not what I had expected. What changes if you let the tone generator play a square, a saw-tooth, or a triangle wave. Describe the FFT patterns. The shapes of the waves change with the different tone generators. The square looks like a square, the saw-tooth is very rough and more rigid, and the triangle is just up and down. Screen capture and paste your graph into your log. What frequencies are strong in your "ahhh" sound? Without changing the pitch of your voice, change the sound from "ahhhh" to "eeee". What happens to the frequencies shown in the FFT display? “Ahhh” “eeee”

Experiment 2 Analyze the data and complete table 2. frequency f wavelength λ temperature T C speed v = λf fork 1 741 0.48 21 351 fork 2 384 0.9 21 350 Compare your experimentally obtained value for the speed of sound with the value obtained from the formula v = (331.4 + (0.6/ o C)T C ) m/s. v = (331.4 + (0.6/21)21)=332 The values obtained for the speed of the sound are higher than the value from the formula. However, they are not too far off.

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