Name ________________________________________ Period ________________ Date _________________
Physics
Chapter 12 Questions Worksheet
Section 1: Sound Waves
1. Whether a sound wave conveys the shrill whine of a jet engine or the melodic
whistling of a bird, it begins with a ___________________ object.
2. The vibrating of a tuning fork sets the air molecules near it in motion As the
prong swings to the right the air molecules in front of the movement are
forced closer together, this region of high molecular density and high air
pressure is called_____________________.
3. As the prong moves to the left the air pressure in this region becomes lower
than normal, this region of lower density and pressure is called______________.
4. Sound waves move out in _________ directions like ripple waves on a pond.
5. In sound waves, the vibrations of air molecules are parallel to the direction of
wave motion. Thus, sound waves are ___________________.
6. The simplest longitudinal wave produced can be represented as a __________
curve.
7. Sound waves that the average human ear can hear, called _____________________,
have frequencies between _______________________________.
8. Sound waves below audible sound and below 20Hz are called _________________.
9. Sound waves above audible sound and above 20,000Hz are called ____________.
10. The frequency of an audible sound wave determines how high or low we
perceive the sound to be, which is know as ______________.
11. As frequency increases, pitch ______________.
12. Sounds generally travel faster through ______________ than _______________.
13. Speed also depends on the temperature of the medium. In gases the particles
collide more frequently as temperature increases. Thus, in a gas, the
disturbance (sound waves) can travel _________________ at higher temperatures.
14. Sound waves travel away from a vibrating source in ____________________________.
15. The circles that represent sound waves represent the centers of compression
called __________________________.
16. The wavelength of sound waves is measured between adjacent _______________.
17. Draw figure 5 below and label observer A, observer B and the source of the
sound. Also label which observer hears a greater frequency than the source
and which observer hears a lesser frequency than the source.
18. The frequency shift heard by the two observers is known as the _______________.
19. The Doppler effect is named for the Austrian physicist __________________.
20. Because frequency determines pitch, the Doppler effect affects the pitch
heard by each listener. Observer A heard a _______________ pitch, while
observer B heard a _____________pitch than the source.
21. The Doppler effect occurs whenever there is _________________ between the
source of the waves and the observer.
22. The Doppler effect is most commonly experienced with sound waves,
however it is a phenomenon common to _______________________.
Section 2: Sound Intensity and Resonance
23. The rate at which the energy is transferred from one air molecule to the next
through a unit area of the plane wave is called the ___________ of the wave.
24. Because power, P, is defined as the rate of energy transfer, intensity can also
be described in terms of power. Write the equation for the intensity of a
spherical wave below.
intensity=
- Note: we will always use the area of a sphere because sound waves
propagate from its source in a sphere.
25. The SI units for power is the ___________. Thus, intensity has units of
_________________________________________ (W/m2)
26. The equation shows that the intensity of a sound wave decreases as the
distance from the source (r) increases because the same amount of
______________ is spread over a _______________ area.
27. The average human can hear frequencies ranging from _____________________.
28. Sounds at low frequencies or high frequencies must be relatively ______________
to be heard, whereas sounds in the middle of the spectrum are audible at
_________________ intensities.
29. The softest sound that can be heard by the average human ear are said to be
at the ________________________________________________.
30. The loudest sounds that the human ear can tolerate correspond to sounds at
_______________________________________________ because sounds with greater
intensities can produce pain in addition to hearing.
31. Just as the frequency of a sound wave determines its pitch, the intensity of a
wave approximately determines its perceived _________________.
32. ____________________________ is the ratio of the intensity of a given sound wave to
the intensity at the threshold of hearing.
33. The measure of loudness is referred to be as the _____________________.
34. A dimensionless unit call the _________________(dB) is used to measure
loudness.
a. What is the decibel level for the following examples?
i. Threshold of hearing ____________________
ii. Whispering______________________
iii. Mosquito buzzing_________________________
iv. Vacuum cleaner_________________________
v. Auto horn at 1m__________________________
vi. Threshold of pain_________________________
35. In the pendulum diagram with the loose rubber band around the pendulums,
when one pendulum is set in motion, its vibrations are transferred by the
rubber band to the other pendulums; this is called a ____________________________.
36. The vibrating strings of a guitar force the bridge of the guitar to vibrate, and
the bridge in turn transfers its vibrations to the guitar body; these forced
vibrations are called ____________________________.
37. Because the guitar body has a _________________________ than the strings do, it
enables the strings’ vibrations to be transferred to the air more efficiently,
thereby ___________________________________________ of the sound produced.
38. The frequency of a pendulum depends on its string length. Thus, every
pendulum will vibrate at a certain frequency, known as its_____________________.
39. When natural frequencies match, oscillations will occur with much larger
amplitude; this is known as ________________________.
40. A striking example of structural resonance occurred in 1940, when the
___________________________________, in Washington, was set in motion by the wind.
41. The collapse of this bridge occurred because the wind matched the bridges
___________________________________________ and caused continuous standing waves.
42. The eardrum vibrates with the sound waves and transfers these vibrations to
the three small bones of the middle ear, known as the _________________, the
________________, and the ___________________.
43. Theses bones in turn transmit the vibrations to the inner ear, which contains
a snail-shaped tube about 2cm long called the __________________.
Complete Practice A on page 415, problems 1-5
Read The Inside Story on Hearing Loss, page 421 and give a 2-3 sentences
interpretation of the passage below.
_____________________________________________________________________________________________
_____________________________________________________________________________________________
_____________________________________________________________________________________________
_____________________________________________________________________________________________
_____________________________________________________________________________________________
Section 3: Harmonics
44. In the first harmonic the center of the string experiences the most
displacement, and so it is an _______________________.
45. Because the distance from one node to the next is always ____________ a
wavelength, the string length must equal λ/2. Thus, the wavelength is
_________________________________(λ=2L.
46. If we plug this length into the wave speed equation and solve for wavelength
we get (write equation in middle of page 422).
47. The frequency of vibration with a wavelength of 2L is called the
_____________________________________ of the vibrating string.
48. The fundamental frequency is the ___________________ possible frequency of a
standing wave.
49. Frequencies that are multiples of the fundamental frequency form what is
called a ____________________________.
50. The fundamental frequency (___) corresponds to the ____________________________,
the next frequency (___) corresponds to the __________________________, and so on.
51. The general equation for a harmonic series of standing waves on a vibrating
string is (write the equation in tan box on page 423) where n is an integer
corresponding to the numbered harmonic of that frequency, L is the length of
the string and v is the wave speed.
52. We will look at these equations and how they work in this chapter together,
however write down the equations for Harmonic Series of a Pipe Open at Both
Ends and Harmonic Series of a Pipe Open at One End below.
53. Trumpets, saxophones, and clarinets are similar to a pipe
______________________________________.
54. For example, even though a trumpet has two open ends, ________________________
effectively closes one end of the instrument.
55. In a saxophone or a clarinet, the ____________ closes one end.
56. The equations for harmonics _______________________ apply to these instruments.
a. Do apply because they are exactly like a pipe open at one or both ends.
b. Don’t apply because of several reasons pertaining to the structure and
design of the instruments.
57. Instruments are capable of playing several harmonics at once. The harmonics
played by the viola are the first, second, third, fourth, fifth, sixth, and ninth
harmonics. These add together according to the _________________________________
to give the resultant waveform. (Draw the waveform for the viola from
column three below)
58. In music, the mixture of harmonics that produces the characteristic sound of
an instrument is referred to as the ______________________________________.
59. From the perspective of the listener, the spectrum results in sound quality, or
_________________.
60. The fundamental frequency of a vibration typically determines ______________.
61. Other harmonics are sometimes referred to ___________________.
62. The frequency of the thirteenth note is exactly twice that of the first note, and
together the 13 notes constitute an ________________.
63. When two waves of ________________ different frequencies interfere, the
interference pattern varies in such a way that a listener hears an alternation
between loudness and softness.
64. The variation from soft to loud and back to soft is called a ______________.
65. A beat is created by the combination of ____________________ and
____________________ interference.
66. The frequency difference between two sounds can be found by the number of
__________ heard per _____________.
Review sample problem B on page 426
Complete Practice B on page 427, problems 1-4