**Your
Answer to Q210.**
Sorry, your answer is **not** correct. What is it that determines the
repeat time?

Help: *Fundamentals of
Sound*, Secs. 7-B, 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 210.

**Hint
for Question 210:** The fundamental is the slowest in returning to its
initial shape. When it finally has, the second harmonic has returned twice,
the third three times, etc.

Return to Question 210

**Your
Answer to Q210. **Congratulations, your answer is **correct**.

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

Return to Question 210

**Correct
Answer to Question 210:** The fundamental is the slowest in returning
to its initial shape. When it finally has, the second harmonic has repeated
twice, the third three times, etc. Thus the mininum time one has to wait is
the period of the fundamental, which is indeed the repeat time of the wave.

Return to Question 210

**Your
Answer to Q215.** Sorry, your answer is **not** correct. Think about
the case where the frequencies present are 20 Hz and 30 Hz with a missing fundamental
of 10 Hz.

Help: *Fundamentals of
Sound*, Secs. 7-B, 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 215.

**Hint
for Question 215:** Say you have just the second and third harmonics
present and no fundamental. What is the first time that the waves will all be
back to their starting shapes?

Return to Question 215

**Your
Answer to Q215. **Congratulations, your answer is **correct**.

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

Return to Question 215.

**Correct
Answer to Question 215:** Say you have just the second and third harmonics
present and no fundamental. The first time that the waves will all be back at
their starting shapes so the wave begins repeating is *still* the period
of the fundamental, even though it is not actually present in the wave. Suppose
the fundamental is 10 Hz, so that the second harmonic is 20 Hz, and the third,
30 Hz. Then after the period of the second harmonic (1/20 s) the third will
have repeated 1.5 times and will not be at its starting shape. The first time
both the second and third harmonics will begin repeating **simultaneously**
is after the period of the fundamental (1/10 s). Thus the statement is false
because on some occasions, at least, it does repeat at the frequency of the
fundamental.

However, there are cases
where the wave repeats **more often** than the fundamental frequency. An
example is a wave that is made up of the second harmonic (20 Hz) plus the fourth
(40 Hz). This wave repeats every 1/20 s, the period of the **second**
harmonic. This is because the fourth harmonic is exactly twice the second, which
acts as if it were a fundamental frequency. (We might call it an "effective
fundamental" or "false fundamental.")

Return to Question 215.

**Your answer to Question 220:** Sorry, your answer
is **not** correct. The frequency spectrum gives you several pieces
of information. What information do you need to draw a waveform?

Help: *Fundamentals of
Sound*, Sec. 7-A.

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 220.

**Hint
for Question 220:** Look at the different complex waves in Figures 6-4
and 6-5 of the *Fundamentals of Sound*. What information do you need to
draw the waveforms shown?

Return to Question 220.

**Your
Answer to Q220. **Congratulations, your answer is **correct**.

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

Return to Question 220.

**Correct
Answer to Question 220:** To draw the pressure versus time graph of
a complex wave you need to know the amplitude, frequency, and **phase** of
the constituent sinusoidal waves. The phase refers to the exact position of
the wave (usually relative to other waves), e.g., whether, say, it is now at
a trough or a crest or elsewhere. Without this information you are unable to
draw the wave shape. a) is the correct answer.

Return to Question 220.

**Your
Answer to Q225.** Sorry, your answer is **not** correct. What determines
pitch? What determines sound quality?

Help: *Fundamentals of
Sound*, Sec.6-F.

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 225.

**Hint
for Question 225:** Pitch is determined by the repeat frequency of the
complex wave, but sound quality is determined by the frequency spectrum.

Return to Question 225.

**Your
Answer to Q225. **Congratulations, your answer is **correct**.

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

Return to Question 225.

**Correct
Answer to Question 225:** Pitch is determined by the repeat frequency
of the complex wave, but sound quality (of a sustained note) is determined by
the frequency spectrum . Thus, if the notes all have the same repeat frequency,
we hear the same pitch, however, what they differ in is the amplitudes of the
different constituent sinusoidal frequencies making up the note, i.e., the nature
of the frequency spectra. a) is correct. b) is wrong because the ear is not
sensitive to phase. c) is also correct because the harmonic series is the same
for each wave if they have the same repeat frequency. d) is wrong because, if
the amplitudes of all frequency components were the same for all three notes,
then they would have the same frequency spectra and would have precisely the
same sound quality. The overall correct answer is e), two of the statements
are true, a) and c).

Return to Question 225.

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