Wave Speed and Sound Flashcards
the _________ of a wave is
the number of complete cycles that pass
a given point in the medium per a unit of
time.
frequency
The frequency of the wave is the same
as the frequency of the ______. It is the
_______ alone that determines the
frequency of the wave.
source; source
Once the wave is
produced, the frequency ______ changes,
even if its speed and wavelength do.
never
Likewise the _____ of the wave can
never change, because it is the _____
of the frequency.
period; inverse
________ is defined as the time it takes to
go a certain distance.
Speed
For a wave, we consider the speed of
the wave to be the distance traveled by
the wave during one ______ or ______ of
the source.
cycle; period
Waves travel ____ wavelength in the time
required for one complete vibration of the
source.
one
Temperature:
Warmer gases transmit waves faster
factors that affect wave speed
temp, properties of the material, (in a string) linear density and tension
Very ______ strings transmit energy more
effectively.
tight
_____ _______ strings also transmit wave
energy more effectively.
Less dense
The linear density, or mass per unit
distance, determines how much _____ it
will take to make the string _______.
force; vibrate
_______ 🡪 Energy that travels as
longitudinal waves. Some parts have
high pressure and some parts have low
pressure.
Sound
The source of every sound is a _________ ________.
vibrating object
in a human voice, what is the vibrating object
vocal chords vibrate
in a guitar, what is the vibrating object
strings on the guitar vibrate
Sound waves need to travel through a
_________ like air. Therefore, there is no
sound in space!
medium
Remember that sound travels by making
air molecules move.
This means that the speed of sound is limited by how fast the molecules can move, which is related to the temperature and density of the medium.
If we ________ the temperature of the molecules, the speed of sound should ________ also.
increase; increase
The speed of sound is also effected by
the ______.
medium
Sound travels most rapidly
in certain ______, less rapidly in many
______, and quite slowly in most _____.
solids; liquids; gases
The ratio of the airspeed of an object to the local speed of sound is called a _____ ________.
Mach number
Mach Number =
airspeed of object / local speed of sound
When an object is travelling at Mach 1, it
is travelling at ____________________
the same speed as sound
When an object is travelling at Mach 2, it
is travelling at ____________________
twice the speed of sound
The audible region of the sound
spectrum for humans is from
20 Hz to 20kHz.
Hz means
1/second (1/s)
Frequencies lower than 16 Hz are called
__________.
Infrasonic
Frequencies higher than 20 000 Hz are
called ________.
ultrasonic
___________ describes how humans
perceive sound energy.
Loudness
The loudness of
a sound wave is based on its _________.
amplitude
The larger the amplitude of the wave, the
________ the sound will be.
louder
The amplitude of a wave is an indication
of how much ________ is being
transferred.
energy
The amount of sound energy being
transferred per unit area is called _______ _________.
sound intensity
_______- 🡪 the amount of sound energy
passing each second through a unit
area.
Intensity
Sound intensity is most commonly
measured in Bells or _________.
Decibels
The intensity of sound _________ as the
distance from the source _______.
decreases; increases
why are transverse waves called secondary waves?
Transverse waves are called secondary waves
because they arrive after the longitudinal wave.
predict what happens to the wavelength of a wave on a string when the frequency is doubled. assume that the tension in the string remains the same
The wavelength is halved.
The speed stays the same because the tension and linear density remain the same.
That means that when the value of f doubles in the equation v = fλ, the value of λ must be divided by two.
predict what happens to the speed of a wave on a string when the frequency is doubled. assume that the tension in the string remains the same
The speed is doubled.
Given the equation v = fλ, when frequency is doubled, for the left side of the equation to equal the right side, the velocity should also be doubled
An aircraft flying at Mach 2 means…
An aircraft flying at Mach 2 means that it is
travelling at a speed equal to double the speed of
the sound at that temperature
explain why the speed of sound varies
The speed of sound varies by temperature and
density of the medium, both of which depend on
the molecular structure of various particles
sound intensity
Sound intensity is a measure of energy per
unit area due to a sound wave
loudness
Loudness is a measure of the sound intensity. It
can also be defined as a human perception of
sound energy
decibel
The decibel is the unit of measurement of
sound level used to describe sound intensity
why are different sounds required for sound intensity and loudness
Loudness is expressed in a logarithmic scale
using decibels (dB).
Decibels are a more convenient measurement unit than watts per square metre (W/m2).
describe the concept of sound intensity
Sound intensity is a measure of energy flowing
through the unit area due to a sound wave.
Vibrations through a gas produce regions where particles are farther apart. What are these regions called?
(a) compressions
(b) rarefied
(c) complex waves
(d) rarefactions
(d) rarefactions
Which of the following are geometric wave
characteristics?
(a) waveform, amplitude, and phase shift
(b) amplitude, crest, and trough
(c) crest, trough, and frequency
(d) period, speed, and frequency
(b) amplitude, crest, and trough
Infrasonic waves have frequencies
(a) below 20 Hz
(b) within the range 20 Hz to 20 kHz
(c) above 20 kHz
(d) within the range 1 kHz to 5.5 kHz
(a) below 20 Hz
The Mach number is the ratio of
(a) force per unit area
(b) airspeed to the local speed of sound
(c) loudness to distance
(d) pressure to speed
(b) airspeed to the local speed of sound
true or false
A longitudinal wave is a wave in which particles
vibrate in a direction that is perpendicular to the
direction of the flow of energy.
false
t or f
The units of a wave’s phase are the same as the unit of the wavelength.
true
t or f
Cooler gases are more effective than warmer gases at transmitting sound.
false
t or f
The amplitude of a longitudinal wave is a difference in pressure.
true
