TUTORIAL ANSWERS 190-200

 
 
 
 


 

Your answer to Q190:  Sorry, your answer is not correct.  What can you vary to make two different-looking waves out of sine waves at 200 and 400 Hz.

Help: Fundamentals of Sound, Sec. 6-C.

Or, would you like a HINT?

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

Return to Question 190.
 


 

Hint for Q190:  What the question means is that the two sine waves at 200 and 400 Hz are added with one relative phase for one total wave and then with another relative phase to form another wave.

    Return to Question 190.


 

Your answer to Q190:  Congratulations, your answer is correct!

    To read the "official" correct answer, click HERE.

    Return to Question 190.
 


 

Correct answer to Q190:  The statement is false. Compare the two waves in Figs. 6-4 and 6-5 of Fundamentals of Sound. The only difference between the two waves is that the 400 Hz wave has a different phase in the two figures. However, the ear is unable to distinguish phase differences (this statement is called Ohm's law) and the two wave forms sound the same.

    Return to Question 190.
 
 
 
 
 

Your answer to Q193:  Sorry, your answer is not correct. You need to know the definition of "phase."

Help: Fundamentals of Sound, Sec. 6-A.

Or, would you like a HINT?

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

Return to Question 193.
 


 

Hint for Q193:  The left wave starts upward at t = 0 and the right one starts down.

    Return to Question 193.


 

Your answer to Q193:  Congratulations, your answer is correct!

    To read the "official" correct answer, click HERE.

    Return to Question 193.
 


 

Correct answer to Q193:  The two waves are not in the same part of their cycles at t = 0 or at any other times; when one is at a crest the other is at a trough. They are said to be "180 degrees out of phase." The statement is false.

    Return to Question 193.
 
 
 
 
 


 
Your answer to Q195:  Sorry, your answer is not correct. What repeat time does a complex oscillatory wave have? What is its reciprocal?

Help: Fundamentals of Sound, Secs. 6-C, 7-B.

Or, would you like a HINT?

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

Return to Question 195.
 


 

Hint for Q195:  Any complex repeating wave can be thought of being made up of a harmonic series of sinusoidal waves. Which of these has the same period as that of the complex wave?

    Return to Question 195.


 

Your answer to Q195:  Congratulations, your answer is correct!

    To read the "official" correct answer, click HERE.

    Return to Question 195.
 


 

Correct answer to Q195:  Any complex repeating wave can be thought of as being made up of a harmonic series of sinusoidal waves added together with some set of amplitudes. The repeat time of the complex wave is the same as the period of the fundamental and its reciprocal is the frequency of the complex wave and of the fundamental. When you take the reciprocal of the repeat time of the complex wave, you immediately have the frequency of the fundamental. The frequencies of all the other harmonics that make up the complex wave are multiples (f0, 2f0, 3f0, etc.) of this fundamental. In this way the statement is true.

    Return to Question 195.
 
 
 
 
 

Your answer to Q200:  Sorry, your answer is not correct.  This question is based on what you learned in Chapter 2 about the harmonic series.

Help: Fundamentals of Sound, Sec. 2-C, 6-D.

Or, would you like a HINT?

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

Return to Question 200.
 


 

Hint for Q200:  The frequency of the second harmonic is just twice that of the first harmonic.

    Return to Question 200.


 

Your answer to Q200:  Congratulations, your answer is correct!

    To read the "official" correct answer, click HERE.

    Return to Question 200.
 


 

Correct answer to Q200:  If the frequency of the first harmomic is f0, then that of the second harmonic is 2f0. If, as this says, the frequency of the first harmonic is one-half that of the second, then its period must be twice as long. The statement is true. This question is relevant to the discussion of Chapter 6 of Fundamentals of Sound, because we can see that it takes the first harmonic the longest time of all the harmonics to repeat itself. After the period of the fundamental, the second harmonic has repeated itself twice, the third three times, etc. Thus a complex repeating wave's repeat time must be the period of the fundamental.

    Return to Question 200.
 
 
 
 
 


 

 


ab_webmaster@abacon.com
©2002 William J. Mullin
Legal Notice