TUTORIAL ANSWERS 240-270

 

 
 

Your Answer to Q240.  Sorry, your answer is not correct. What determines pitch?

Help: Fundamentals of Sound, Sec. 7-D.

Or would you like a HINT?

You should try to work out the answer on your own, but if you insist on reading it the correct answer is here .

Return to Question 240.

 

 

Hint for Question 240:  Pitch is determined by repeat frequency. How do you determine that?
 
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Your Answer to 240. Congratulations, your answer is correct.

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Correct Answer to Question 240:  Pitch is determined by repeat frequency. You determine the repeat frequency f by the rule that f is the largest common factor of the frequencies in the spectrum. In I this is just the fundamental f0 = 100 Hz. In III and V, the repeat frequency is again f0 even though that frequency is not actually in the spectrum. However the frequencies that are present are multiples of f0, and that is the largerst common factor. II contains harmonics that are all multiples of 200 Hz so that is the repeat frequency. In the same way the repeat frequency of VI is 200 Hz, since the sixth harmonic, 600 Hz is three times 200 Hz. In IV, the repeat frequency is 300 Hz since the other frequency component, 600 Hz, is twice that.

Thus III and V have the same repeat frequency as I . a) is correct.
 

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Your Answer to Q250.  Sorry, your answer is not correct.  What are the two features of this wave that makes it possible to distinguish among the spectra?

Help: Fundamentals of Sound, Sec. 7-B.

Or would you like a HINT?

You should try to work out the answer on your own, but if you insist on reading it the correct answer is here .

Return to Question 250.

 

 

Hint for Question 250:  Note that the wave is symmetric and that it has four nodes. That information should allow you to determine the spectrum.
 
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Your Answer to 250. Congratulations, your answer is correct.

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Correct Answer to Question 250:  Because the wave is symmetric (that is, the right part is the mirror image of the left) then the wave spectrum contains only symmetric harmonics. These are the odd harmonics, f0, 3f0, 5f0, etc. This means that only c) and d) qualify. However, because the wave has four nodes and looks a lot like the third harmonic, we expect that the amplitude of this harmonic will dominate the spectrum as in d) which is the correct answer.

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Your Answer to Q255.  Sorry, your answer is not correct.  Use the rule for finding the repeat frequency.

Help: Fundamentals of Sound, Sec. 7-D.

Or would you like a HINT?

You should try to work out the answer on your own, but if you insist on reading it the correct answer is here .

Return to Question 255.

 

 

Hint for Question 255:  The repeat frequency is the largest common factor of the frequencies in the spectrum.
 
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Your Answer to 255. Congratulations, your answer is correct.

If you would like, you can compare your answer to the "official" correct answer .

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Correct Answer to Question 255:  The repeat frequency is the largest common factor of the frequencies in the spectrum, which is 6 Hz. The repeat time is the inverse of this or 1/6 s.

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Your Answer to Q260.  Sorry, your answer is not correct.  How do you determine the repeat frequency?

Help: Fundamentals of Sound, Sec. 7-D.

Or would you like a HINT?

You should try to work out the answer on your own, but if you insist on reading it the correct answer is here .

Return to Question 260.

 

 

Hint for Question 260:  The repeat frequency is always the fundamental or one of the higher harmonics, depending on the spectrum.
 
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Your Answer to 260. Congratulations, your answer is correct.

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Correct Answer to Question 260:  The repeat frequency is always the fundamental or one of the higher harmonics, depending on the spectrum. The longest it could be is the period of the fundamental. If one of the higher harmonics is the repeat frequency than the repeat time is shorter. The statement is true.

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Your Answer to Q270.  The correct answer is 15 Hz. If you did not get that correct, try again.

Help: Fundamentals of Sound, Sec. 7-D.

Would you like a HINT?

Read the "official" correct answer here.

Return to Question 270.

 

 

Hint for Question 270:  What is the rule for determining the repeat frequency?
 
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Your Answer to 270. Congratulations, your answer is correct.

If you would like, you can compare your answer to the "official" correct answer 

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Correct Answer to Question 270:  To determine the repeat frequency, you must find the largest common factor of the frequencies present in the spectrum. These frequencies are 30, 45, and 90 Hz. The largest common factor is 15 Hz. The frequencies are respectively 2, 3, and 6 times 15 Hz. Thus the repeat frequency is 15 Hz.

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