Comd 3400 Acoustics Book Exam 1

Front 1

what is undisturbed air said to be in?

Back 1

a constant state of equilibrium

Front 2

What happens when an external force impinges upon air particles?

Back 2

compressions, and rarefactions

Front 3

what are compressions?

Back 3

air molecules move closer together

Front 4

what are rarefactions?

Back 4

air partices move farther apart

Front 5

Air is considered a ______, what does air also have?

Back 5

fluid, mass

Front 6

since air is a fluid wht does it do?

Back 6

flow from regions of higher pressure to regions of lower pressure

Front 7

since air is a mass what does it do?

Back 7

exhibits inertial properties, once put into motion, remains in motion, until the energy imparted is dissipated.

Front 8

What happens when disturbance of air particles is dissipated?

Back 8

disturbance of air particles initiated by sharp clap of hands, layer of compressed air moves outward in all directions, compress air ahead, rarefied air trail behnid

Front 9

____ moves in a wavelike fashion in air not ____ particles

Back 9

disturbance, air

Front 10

What is sound thought of?

Back 10

flow of power, transfer of energy

Front 11

_______________motion back and forth, there is a _________ increasing with displacement, always directed toward the position of rest

Back 11

vibratory , restoring force

Front 12

vibratory motion is called what, when it occurs in equal time intervals/

Back 12

periodic

Front 13

displacement, amplitude, frequency, period, and phase, are 5 important measurable characteristics of what?

Back 13

vibratory motion

Front 14

what is displacement?

Back 14

vibrating body at any instant, the distance from equilibrium to the position of the body at tht instant

Front 15

amplitude

Back 15

vibration is the maximum displacment of body from its position of equilibrium,

Front 16

amplitude

Back 16

= to half the total extent of vibration

Front 17

amplitude also called?

Back 17

peak amplitde

Front 18

peak to peak amplitude is what/

Back 18

maximum displacement in one direction plus maximum displacment in the other

Front 19

frequency, f

Back 19

# of complete vibrations or cycles per unit time,

Front 20

frequency , f measured as

Back 20

vibrations, cycles per second cps

Front 21

period, T of vibrating body

Back 21

time elapsed during single complete vibration

Front 22

freq and period are ____

Back 22

recipricals

Front 23

recipricals example: body makes 60 vibrations per second, frequency is 60 hz, each vibration occurs in 1/60 sec period is ____

Back 23

1/60 seconds, or divide it

Front 24

what describes vibratory and wave motion, describes the relationship between 2 or move vibrations, or wave motions?

Back 24

phase

Front 25

________is the portion of a cycle through which a _______ has passed up to a given instant

Back 25

phase, vibrating body

Front 26

phase change in complete vibratory cycle is ________

Back 26

360 degrees

Front 27

the object begins its vibration is called a___________

Back 27

starting phase ( 0 degrees)

Front 28

________ is the simplest form of vibratory motion, executed by tines of tuning fork, by ____ through small arc or by weight bopping up and down on an ideal spring

Back 28

simple harmonic motion, pendulum

Front 29

simple harmonic motion abbreivated

Back 29

SHM

Front 30

________ defined as projected uniform circular motion

Back 30

simple harmonic, or sinsoidal motion

Front 31

___________ is greatest when displacment is at ________

Back 31

potential energy, maximum

Front 32

__toward ________ is at maximum

Back 32

acceleration , equilibrium,

Front 33

________ toward minimum, when __________is at a maximum

Back 33

kineticc energy, displacment

Front 34

when displacment is at maximum, and kinentic energy is a minimum?

Back 34

mass actually stops for an instant, changes direction, begins moving in opposite direction

Front 35

_________represents a constant exchange of kinetic and potential energies

Back 35

simple harmonic motion

Front 36

_________ has maximum kinetic energy at pt __. the pt of _______, and ______ is 0

figure 6.2

Back 36

mass, 0, equilibrium, potential energy is maximum, kinetic energy

Front 37

mass is displaced and released________ occurs

Back 37

free vibration

Front 38

what is free vibration?

Back 38

system would go into vibration at a rate dependent, on the stiffness of the spring, and the mass of the bob

Front 39

free vibration, a small amount of work is done to overcome____

Back 39

friction

Front 40

___ of_____ decreases with every vibratory cycle

Back 40

amplitude, vibration

Front 41

________ is the decrease in the amplitude of sucessive vibrations

Back 41

damping

Front 42

rate of decrease of amplitude is called_________

Back 42

damping constant

Front 43

a vibrating body is immersed in, or coupled to a propagating medium __________ occurs

Back 43

wave motion

Front 44

wave motion is either __ or ____

Back 44

transverse, longitudinal

Front 45

any medium that supports a _______ transmits transverse waves

Back 45

shearing stress

Front 46

________ can only be subjected to compressional stress

Back 46

liquids

Front 47

____________ transmitted by any matter that responds to compression and has elasticity

Back 47

longitudial waves

Front 48

all forms of matter will transmit___________, because all forms of matter exhibit compressional density

Back 48

longitudinal waves

Front 49

________ happens with the propagation of sound in air

Back 49

longitudinal wave motion

Front 50

___ is a disturbance that is traveling through the air

Back 50

progressive wave motion

Front 51

_______ is the direction of each molecule of the medium is parallel to the direction of propagation of the disturbance

Back 51

progressive longitudinal wave

Front 52

each molecule of the___ executes the same motion as the preceding molecule, but a short interval of time later

Back 52

propagating medium

Front 53

_________ distinctive characterstic is the displacement of the individual particles is perpendicular to the direction of the propagation of the wave

Back 53

transverse wave

Front 54

________ represent the velocity of air particle movement, as well as the extent and frequency of movement

Back 54

sine curve

Front 55

_____ differ in _____, and_____ and frequency

Back 55

sine waves, amplitude, starting phase,

Front 56

sound vibrators are usually in 3 categories _____, _____, or__

Back 56

free, forced, maintained

Front 57

________, include tuning forks, pendulums, and vibrating strings

Back 57

free vibrators

Front 58

____ continue to vibrate periodically until the energy has been dissipated

Back 58

free vibrators

Front 59

_________ vibrate at its own ____

Back 59

free vibrators, natural frequency

Front 60

rate of ________-- is same no matter where string, plucked, bowed

Back 60

vibration

Front 61

_______ of tuning forks, is dependent upon the mass, and stiffness of their tines

Back 61

rate of vibration

Front 62

____________ absorbs sound energy best when the energy source has a frequency rate exactly the same as the vibrator

Back 62

free vibrator

Front 63

_________-- is the characteristic of the free vibrator to absorbs sound energy best when the energy source has a frequency rate exactly the same as the vibrator

Back 63

resonance

Front 64

________ when vibratory or sound energy is imparted to a structure at a frequency rate other than its own natural frequency

Back 64

forced vibration

Front 65

stem of turning fork held firmly against table top, the whole table set into __ at the same rate as the tuning fork

Back 65

vibration

Front 66

if vibrating fork is removed from table ______of the table cease almost instantly

Back 66

vibrations

Front 67

table offers a great deal of resistance to _____ at the rate of the fork, and the vibrations are _______

Back 67

vibrations, highly damped

Front 68

__-occurs when a displaced body, returns to its position of equilibrium without passing through it

Back 68

extreme damping

Front 69

____________ is a constant quanity of energy applied to the vibrator at an intergral mulitple of the natural frequency of the vibrator

Back 69

maintained vibration

Front 70

with_______, any damping effects can be overcome, permits the vibrator to maintain a constant amplitude of vibration

Back 70

maintained vibration

Front 71

________ is a constant quanity of energy is applied to the vibrator at an integral multiple of the natural frequency of the vibrator

Back 71

maintained vibration

Front 72

phase change 360 degrees, is a complete cycle of

Back 72

simple harmonic motion

Front 73

______ can be measured from any 2 pts tht represent a 360 degrees phase change

Back 73

wavelength

Front 74

_____which sound waves travel through air is 1130 ft per sec,

Back 74

velocity

Front 75

___ is velocity in feet per second

Back 75

v

Front 76

__ is the frequency in HZ

Back 76

f

Front 77

__ of a sound wave determined by the ____ of vibration of the source of sound

Back 77

frequency, frequency

Front 78

____ is a sinusoidal note, with a frequency of 440 HZ,

Back 78

pure tone

Front 79

____________ is proportional to the square of the amplitude

Back 79

energy of the sound wave

Front 80

sounds in air are ______ and ______

Back 80

compressions rarefactions

Front 81

maximum displacement (compression or rarefaction) _____ velocity is zero, but as the __________ pass through portions of equlibrium ____ is maximuum

Back 81

air particle, air particles, velocity

Front 82

_______ constitutes a region of increased air pressure, exerts force on adjacent particles equally and in all directions,

Back 82

compressional wave

Front 83

___ is the rate of energy flow per unit of area, of surface receiving the flow.

Back 83

intensity

Front 84

as the distance from the sound source____, the distribution of energy flow must ________ because intensity is the rate of energy flow per unit of area of surface receiving the flow

Back 84

increases, decrease

Front 85

sound is reflected when encounter______

Back 85

interface

Front 86

_______ is the boundary between 2 propagating mediums that have differrent physical properties

Back 86

interface

Front 87

_______ reflected at compression at barrier, and ______ at free end

Back 87

comprssion wave, rarefaction

Front 88

_____ common in acoustics are walls, ceilings, floors of the rooms we live and work in

Back 88

interfaces

Front 89

____________ wave initially generated at the source,

Back 89

incident wave

Front 90

________ moving away from wall

Back 90

reflected wave

Front 91

if reflecting barrier is large sound complies with _____________ that states the angle of incidence is equal to the angle of reflection

Back 91

law of reflection

Front 92

________ and ____ waves are encountered in rooms, and are multiple reflections, when superposed results in interference

Back 92

incident, reflected