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Chapter 12: Q1MCQ (page 328)

Do you expect an echo to return to you more quickly on a hot day or a cold day?

(a) Hot day.

(b) Cold day.

(c) Same on both days.

Short Answer

Expert verified

The correct option is (a).

Step by step solution

01

Understanding sound’s echo

A sound produced by the reflection of sound waves from a surface back to the listener (with delay) is called an echo. The delay is directly proportional to the distance of the reflecting surface from the source and listener.

Example: The repeating of a sound created by footsteps in an empty marble hallway.

02

Explanation

Students may answer that the speed of sound is the same if they do not understand that the speed of sound is not constant but depends upon the temperature of the air. The sound rate is more significant when it is hotter, so it takes less time for the echo to return.

Hence, the correct option is (a).

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Most popular questions from this chapter

How will the air temperature in a room affect the pitch of organ pipes?

Why are the frets on a guitar (Fig. 12–30) spaced closer together as you move up the fingerboard toward the bridge?

FIGURE 12–30 Question 9.

Question: (III) When a player’s finger presses a guitar string down onto a fret, the length of the vibrating portion of the string is shortened, thereby increasing the string’s fundamental frequency (see Fig. 12–36). The string’s tension and mass per unit length remain unchanged. If the unfingered length of the string is l= 75.0 cm, determine the positions x of the first six frets, if each fret raises the pitch of the fundamental by one musical note compared to the neighboring fret. On the equally tempered chromatic scale, the ratio of frequencies of neighboring notes is 21/12.

Figure 12-36

Question: In audio and communications systems, the gain, \(\beta \) in decibals is defined for an amplifer as,

\(\beta = {\bf{10log}}\left( {\frac{{{P_{{\bf{out}}}}}}{{{P_{{\bf{in}}}}}}} \right)\)

Where \({P_{{\bf{in}}}}\) is the power input to the system and \({P_{{\bf{out}}}}\) is the power output. (a) A particular amplifer puts out 135 W of power for and input of 1.0 mW. What is its gain in dB? (b) if a signal to noise ratio of 93 dB is specified, what is the noise power if the output signal is 10 W?

Question: (II) (a) Estimate the power output of sound from a person speaking in normal conversation. Use Table 12-2. Assume the sound spreads roughly uniformly over a sphere centered on the mouth. (b) How many people would it take to produce a total sound output of 60 W of ordinary conversation? (Hint: Add intensities, not dBs.)
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