Chapter 26 - Sound

Resonance occurs when _____.

an object is forced to vibrate at its natural frequency

A 680-Hz sound wave travels at 340 m/s in air, with a wavelength of _____.

0.5 m

When the handle of the tuning fork is held solidly against a table, the sound becomes louder and the length of time the fork vibrates _____.

becomes shorter

Noise-canceling earphones are an example of _____.

destructive interference

Compared to the threshold of hearing, a sound level of 10 decibels is _____.

10 times more intense

Compared to sound of 10 decibels, a sound of 50 decibels has _____.

10,000 times the intensity

Suppose you sound a tuning fork at the same time you hit a 1053-Hz note on the piano and hear 3 beats/sec. You tighten the piano string very slightly and now hear 4 beats/sec. What is the frequency of the tuning fork?

1050-Hz

How many times a minute will you be in step with a friend when you walk at 77 steps per minute and your friend walks at 65 steps per minute?

12

A tuning fork of frequency 300 Hz will resonate if a sound wave incident on it has a frequency of _____.

150 Hz

A sound wave that has a wavelength of 2 m in room temperature air has a frequency of about _____.

170 Hz

A general rule for estimating the distance in kilometers between an observer and a lightning bolt is to count the number of seconds between seeing and hearing the bolt, and divide by _____.

3

Two whistles produce sounds of wavelengths 3.4 m and 3.2 m. What is the beat frequency produced?

6.3 Hz

The speed of sound in dry air at 20 degrees Celsius is 340 m/s. How far away is a jet plane when you notice a 2 second delay between seeing the plane and hearing it?

680 m

An oceanic depth-sounding vessel surveys the ocean bottom with ultrasonic sound that travels 1530 m/s in seawater, and finds a 10-second time delay of the echo to the ocean floor and back. The ocean depth there is _____.

7650 m

Beats are produced when two tuning forks, one of frequency 240 Hz and the other of frequency 248-Hz, are sounded together. The frequency of the beats is _____.

8 Hz

Write a short paragraph on beats and how they are produced. Give examples.

Beats are produced by interference of different frequencies between waves. Example: 248 Hz - 242 Hz = 6 Beats/sec

In which one of the following does sound travel the fastest?

Ice

Sound waves cannot travel in _____.

a vacuum

Sound waves in air are a series of _____.

all of the above (high and low pressure regions, periodic disturbances, periodic condensations and rarefactions)

A 1134-Hz tuning fork is sounded at the same time a piano note is struck. You hear three beats per second. What is the frequency of the piano string?

Not enough information given to determine (1134, 1131, 1137, 2268)

What is resonance and what conditions cause it?

Resonance is forced vibration by something vibrating at an object's natural frequency.

What is sound, and how does it propagate through the air?

Sound is a longitudinal wave made up of compressions and rarefactions that vibrate air molecules.

Beats can be heard when two tuning forks _____.

have almost the same frequency and are sounded together

The phenomenon of beats results from sound _____.

interference

A sound wave is a _____.

longitudinal wave

If the sounding board were left out of a music box, the music box would _____.

make little "plinks" that you could hardly hear

An explosion occurs 340 km away. Given that sound travels at 340 m/s, the time the sound takes to reach you is _____.

more than 200 s

A singer shattering crystal glass with her voice is a demonstration of _____.

resonance

The Tacoma Narrows Bridge collapsed due to _____.

resonance

Compared to the speed of light, sound travels _____.

slower

Which of the following would be most likely to transmit sound with the highest speed?

steel in a bridge

The speed of a sound wave depends on _____.

the air temperature

Sound waves are produced by _____.

vibrating objects

Sound travels faster in air if the air is _____.

warm