Exam 1

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99 Terms

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for sound to exist there must be
source

force

medium
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initial force it makes to move something=
more force
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elasticity
capacity to recover (return to original shape) from shape volume distortion

\-when we put something into vibration, it has to come back, how waveforms are created

capacity to recover from shape/volume/position/distortion

desire to return to its original form
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equillibrium
state of rest
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displacement force
initial shift away from equilibrium
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inertia
tendency to resist a change in motion/velocity

\-proportional to mass
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Momentum
momentum: unit of motion mass x velocity

\-greater mass, greater momentum

\-uniform motion
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Newtons First Law of Motion
all bodies remain at rest, or in a state of uniform motion, unless another force acts in opposition
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restorative force
return to equilibrium
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Newtons Third Law of Motion
with every force there must be an associated equal reaction force of opposite direction
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At initial equilibrium
inertia is maximal

restoring force is zero

velocity is zero

momentum is zero
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At maximum displacement
inertia is zero

restoring force is

velocity is zero

momentum is zero
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As an object returns to equilibrium
restoring force is maximal

velocity is maximal

momentum is maximal
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One vibratory cycle
equilibrium → maximum displacement in one direction → back to equilibrium → maximum displacement in opposite direction → back to equilibrium (in the absence of other forces)
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vibration
repeated (uniform) cycles due to interaction of momentum and restoring force (elasticity)
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tuning fork= vibratory source → displacing all molecules
medium=air

vibratory motion of fork exerts intermittent force on air molecules

air molecules collide with each other=mechanical wave
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compression
displacement in one direction

getting closer together

increase in density
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rarefaction
restoring movement in other direction causes rarefaction

spreading apart

decrease in density
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consecutive rarefaction and compressions form
wave propagation
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frequency
cycles per second

rate of vibratory movement

\*frequency of vibration of transmission medium is the same as frequency of vibration of the source
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characteristics of the vibratory source
density

length

tension

\*all determine how fast something can vibrate
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speed of wave propagation
speed of wave propagation os governed by properties of the medium

(speed of sound will be different in places of lower altitude, cant physically tell though)
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speed of sound waves
s=square root of elasticity (e) over the density (p)
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Speed of sound waves

bigger elasticity…
faster speed of propagation
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speed of sound waves

high density…
slower speed
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elasticity is higher in …
solids
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the more tightly bonded the particles are to each other, the more resistant they are to displacement
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sound moves … through air with higher temps
faster
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transverse wave
direction of vibration of the medium is perpendicular to the direction of wave propagation
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longitudinal wave
direction fo particle movements is parallel to the direction of wave propagation
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sound waves are always …. waves
longitudinal
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simplest sound
pure tone

vibration repeats itself in exactly the same way

creates a simple harmonic motion within air molecules
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simple harmonic motion
repetitive movement back and forth through an equilibrium, so that the maximum displacement on one side of this position is equal to the maximum displacement on the other side
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simple harmonic waveforms can be added together to create…
any sound
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why can simple harmonic motions be represented in a circular motion?
constant change in magnitude and direction; repeats the exact same way each time
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five characteristics of a sound wave
frequency

period

wavelength

phase

amplitude

\*fundamental to how we hear/produce speech sounds
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frequency
the rate at which the vibratory source vibrates back and forth

(hz)

number of cycles per second
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particles within transmission medium vibrate at the … frequency
same
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medium of transmission will vibrate at the… frequency of vibratory source
same
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the frequency with which a source of sound vibrates is governed by the properties of the source
maximum displacement capacity

mass: how to overcome the initial force

stiffness/elasticity: how quickly the balance will shift with displacement force
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natural frequency for stable sources
sources with stable mass and stiffness have a consistent natural frequency/fundamental frequency

ex:tuning forks will always have the same natural frequency at which it vibrates
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Stable sources frequency formula
natural frequency is equal to the square root of stiffness is divided by mass
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something with greater stiffness has a …. natural frequency

(stable sources)
higher
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something with greater mass has a … natural frequency

(stable sources)
lower
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stiffness increases and mass stays stable →vibrate frequency …

(stable sources)
increases
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mass increases, stiffness stays the same → …frequency

(stable sources)
lower
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dynamic sources have the capacity to change shape and/or tension
example: guitar strings
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(dynamic sources)

directly proportional to tension…
when tension is increases, so is frequency
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(dynamic sources)

inversely proportional to length and to cross section mass…
when length or mass is increases, frequency is lower
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(dynamic sources)

length decreases → frequency
increases
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(dynamic sources)

length and tension stay the same, cross sectional mass increases → frequency…
decreases
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octave
the interval between two “notes”/keys where one is exactly one is exactly double the frequency of the other
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semitone
one “step” in western musical scale, the difference in the frequencies between two adjacent piano keys
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the relationship between Hz and “notes”/keys is …
logarithmic
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pitch
perceptual correlate of frequency
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if frequency increases, we perceive the pitch to…
increase
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frequency is a … phenomenon, which can be measured
physical
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pitch doesn’t have a unit, its …
psychological
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if pitch goes up, frequency goes…
up
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period
the elapsed time to complete one cycle of vibration

units: seconds/cycle
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periodicity
the times per cycle is consistent
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periodicity
the time per cycle is not consistent
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period and frequency are
inversely proportional
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shorter period: … frequency
higher
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longer period: … frequency
lower
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wavelength
the distance travelled by one cycle of vibration
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wavelength refers to the cycle … whereas frequency and period refer to aspects of ……
distance

cycle time
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wavelength formula
speed of sound = 331 m/s → speed of sound moves faster in higher temps
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speed of sound is … underwater
faster
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wavelength and frequency are ……
inversely proportional
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wavelength and velocity …..
directionally proportional
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wavelength increases, frequency…
decreases
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wavelength increases velocity…
increases
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Phase
the course of travel from a reference point
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phase is
really important for sound
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Constructive Interference
co-occurring sounds that both dispense in the same direction at the same time have and additive effect when combined

occur anytime the waveforms have overlapping direction of what phase they’re in

effect is greatest when waves are completely in phase
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Interactive Interence
phase offset at 90 degrees

Interactive effect limited because of relative position to equilibrium

“it complicated”
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Destructive Interference
signals 180 degrees out of phase

exactly the opposite of each other

flat line
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Amplitude
degree if displacement/excursion from equilibrium within a vibratory cycle

reflects strength/magnitude/energy of wave

directionally proportional to its original force
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Four Types of Amplitude
instantaneous

Peak/Maximum

Peak-to-peak

Root mean square (RMS)
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instantaneous amplitude
amount of displacement at a particular point in time for phase angle
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Peak Amplitude
furthest displacement from equilibrium (typically at a 90 degree angle)
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Peak to Peak Amplitude
is the absolute difference between maximum positive and negative displacements
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Root mean square amplitude
average amplitude all the way across the waveform

essentially the standard deviation of waveform
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amplitude
amount of energy potential within a wave (volts)
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energy
capacity to do work (joules)
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power
rate at which energy is transferred/expanded (joules/second, watts)
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intensity/sound pressure
flow of sound power through/over a given area
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Acoustic Intensity
an idealized point source of sound is located in free, unbounded medium

energy is transferred from the point source as an ever expanding sphere

loudest at the source
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Acoustic Intensity → sound pressure
intensity is the rate at which sound energy is being transferred through a given area

sound pressure: reflects the compression of air particles associated with the propagation of a sound wave over a given area

sound pressure is the functional measure of sound amplitude
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absolute measure
made directly and independently, single definitive wave
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relative measure
context specific value in comparison to another wave
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absolute measure of sound
definitive measure
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relative measure of sound
comparison/ratio of the absolute power in one sound wave to another
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sound amplitude is commonly reported in…
decibels
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decibel
a ratio that reflects the relative intensity or pressure of a sound compared to a specified reference level

nonlinear units if messure based on logarithms
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damping
the decrease in the amplitude of displacement over time
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ordinate
y axis

vertical axis

intensity/power of sound
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abscissa
x axis

horizontal axis

represented by time