The Origin of Sound
All ____________ are produced by the _________________ of
material objects. These objects cause __________ and _________
pressure zones, forming a sound ________, which travels out in all
directions. As these waves make contact with your
________________, you perceive these pressure fluctuations as
sound.
The frequency of these waves hitting your eardrum is interpreted
as the __________ of the sound. A young person typically can
hear frequencies in the a______________ or s___________ range,
which is _____ Hz to ____________ Hz. Sounds above this range
are called ____________________, while sounds below this range
are called ____________________.
Sound in Air
Sound is a ________________________ wave, because its
medium (________) vibrates ________________ to the wave
speed or energy flow. A sound is composed of high pressure
regions (________________________) followed by low pressure
regions (________________________). In a compression, _____
_________________ are packed closely together and have
____________ than usual pressure. In a rarefaction, _______
__________________ are spread out and have __________ than
average pressure.
Media That Transmit Sound
Most sounds you hear are transmitted through the _______.
Sounds also travel through l____________ and s___________ too
though. Actually sounds travel __________ the more d________
its medium.
Sound is a longitudinal wave, but it is also a
____________________ wave too. This means that it needs a
____________ to travel. (Conversely is the
____________________________ wave, which needs no external
medium to travel.) If you were to put a bell in a jar and suck all
the air out, you would no longer hear the bell because there would
be no m____________ for the e___________ to get off of its
vibrating source.
Speed of Sound
Speed of sound is different than the speed of light. Einstein said
that the speed of light always stays the same. However, sound’s
speed varies depending on the m__________ it is traveling
though. The more e_______________ the medium, the
____________ sound can travel though.
In air, sound is affected by ______________________. The
____________ the air, the ____________ the sound will travel.
__________ __________ and _____ ______________________
are ________________ proportional.
The equation to determine speed of sound in air is:
Note: Temperature must be in _________________.
For example: Sound travels __________ m/s in 25 ºC air.
The speed of sound plays a role in the formation of an echo. An
echo occurs when a sound wave ______________ off of a barrier.
When there is a noticeable __________ between the source and the
reflected sound, an ________ occurs. When the echo comes back
so fast it is not possible to notice any delay (______ seconds or
less) it is called a ____________________.
Loudness
Loud sounds have large __________________, and soft sounds
have small __________________. Amplitude tells you how much
_____________ a wave is carrying. A pressure-time graph of a
loud sound would look like :
while a pressure-time graph of a soft sound would look like:
Intensity of a sound is the _________________ divided by the
_________. Intensity can also be thought of as
___________________ of energy or the ___________________ of
a sound to your ______________.
Intensity is related to the decibel scale. Decibels were named after
______________________________, inventor of the
__________. The decibel scale is weird because it is not a linear
scale; it is a _____________ scale. On the decibel scale, the
reading of zero is associated with ____________ __
___________________, which is the ________ sound you can
hear. A decibel level of 10 is associated with rustling _______ or
normal ______ing which is only 10 decibels higher than the
threshold of hearing but it is ______ _______ as intense. A
_______ has a decibel level of 20; it is ______ times as intense as
the threshold of hearing. Generally, increasing by 10 decibels
____________ the intensity by ______ and increasing the decibel
level by 10 multiplies the loudness by _____.
Forced Vibration
If you play a guitar string that is not on a guitar, it will produce a
_______ sound, but if it is on the guitar, it will make a much
_______ sound. This is because the _______ is forced to
________ at the same _________ as the string, and its larger
surface sets more ________ in motion.
Natural Frequency
When any object composed of an elastic material is disturbed, it
vibrates at its own set of ________________, which together form
its special sound, or _____________ __________________.
When these sounds form a __________________ pattern, we call
the resulting sound __________, and we say the individual
frequencies are __________________. When the resulting
interference pattern does not ____________, we just call the
resulting sound __________, and we say the individual frequencies
are ________________.
Resonance
When the frequency of forced vibration ____________ the object’s
______________ __________________, __________________
occurs. In resonance, the object’s vibration will undergo
__________ __________________ in __________________.
Interference
Sound waves can interfere, like any waves can. Since sound
waves are _______________________, they consist of
compressions and ___________________. When two waves
overlap simultaneously in the same medium, two compressions can
combine to form an ultra ____________________, which will
sound ____________ than normal, and two rarefactions could
combine to form an ultra __________________, which will sound
___________ than normal.
It is also possible for one compression to line up on a rarefaction.
In this case, the two will ___________________ interfere,
producing __________________. This concept is used everyday
in __________-canceling ___________________.
Beats
Beats occur when two sound waves which are very close in
________________ hit your ears simultaneously. Because of the
alternating ___________________ and ____________________
interference, the resulting sound has a _____ -_____ (warbling
effect). The frequency of the hi-lo pattern is called the ________
frequency, which will be equal to the ____________________ in
frequencies.
The Origin of Sound
Sounds
Vibration
High
Low
Wave
Ear drum
Pitch
Audible
Sonic
20
20000
ultrasonic
infrasonic
Sound in Air
longitudinal
air
parallel
compressions
rarefactions
air molecules
higher
air molecules
lower
Media That Transmit Sound
air
liquids
solids
better
dense
mechanical
medium
electromagnetic
medium
energy
Speed of Sound
medium
elastic
better
temperature
hotter
faster
sound speed
air temperature
directly
velocity of sound = 331.5 + .6 (air
temperature in Celsius)
Celsius
346.5
bounces
delay
echo
.1
reverberation
Loudness
amplitude
amplitude
energy
power
area
concentration
harmfulness
hearing
Alexander Graham Bell
Telephone
Logarithmic
Threshold of hearing
Softest (quietest, faintest, etc)
Leaves
Breathing
Ten times
Whisper
100
multiplies
10
2
Forced Vibration
small
louder
guitar
vibrate
frequency
air
Natural Frequency
frequencies
natural frequency
repeating
music
consonant
repeat
noise
dissonant
Resonance
matches
natural frequency
resonance
large
increases
amplitude
Interference
longitudinal
rarefactions
compression
louder
rarefaction
softer
destructively
silence
noise
headphones
Beats
frequency
constructive
destructive
hi-lo
beat
difference