Studied by 5 peoplefor sound to exist there must be
source
force
medium
initial force it makes to move something=
more force
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
equillibrium
state of rest
displacement force
initial shift away from equilibrium
inertia
tendency to resist a change in motion/velocity
-proportional to mass
Momentum
momentum: unit of motion mass x velocity
-greater mass, greater momentum
-uniform motion
Newtons First Law of Motion
all bodies remain at rest, or in a state of uniform motion, unless another force acts in opposition
restorative force
return to equilibrium
Newtons Third Law of Motion
with every force there must be an associated equal reaction force of opposite direction
At initial equilibrium
inertia is maximal
restoring force is zero
velocity is zero
momentum is zero
At maximum displacement
inertia is zero
restoring force is
velocity is zero
momentum is zero
As an object returns to equilibrium
restoring force is maximal
velocity is maximal
momentum is maximal
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)
vibration
repeated (uniform) cycles due to interaction of momentum and restoring force (elasticity)
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
compression
displacement in one direction
getting closer together
increase in density
rarefaction
restoring movement in other direction causes rarefaction
spreading apart
decrease in density
consecutive rarefaction and compressions form
wave propagation
frequency
cycles per second
rate of vibratory movement
*frequency of vibration of transmission medium is the same as frequency of vibration of the source
characteristics of the vibratory source
density
length
tension
*all determine how fast something can vibrate
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)
speed of sound waves
s=square root of elasticity (e) over the density (p)
Speed of sound waves
bigger elasticity…
faster speed of propagation
speed of sound waves
high density…
slower speed
elasticity is higher in …
solids
the more tightly bonded the particles are to each other, the more resistant they are to displacement
…
sound moves … through air with higher temps
faster
transverse wave
direction of vibration of the medium is perpendicular to the direction of wave propagation
longitudinal wave
direction fo particle movements is parallel to the direction of wave propagation
sound waves are always …. waves
longitudinal
simplest sound
pure tone
vibration repeats itself in exactly the same way
creates a simple harmonic motion within air molecules
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
simple harmonic waveforms can be added together to create…
any sound
why can simple harmonic motions be represented in a circular motion?
constant change in magnitude and direction; repeats the exact same way each time
five characteristics of a sound wave
frequency
period
wavelength
phase
amplitude
*fundamental to how we hear/produce speech sounds
frequency
the rate at which the vibratory source vibrates back and forth
(hz)
number of cycles per second
particles within transmission medium vibrate at the … frequency
same
medium of transmission will vibrate at the… frequency of vibratory source
same
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
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
Stable sources frequency formula
natural frequency is equal to the square root of stiffness is divided by mass
something with greater stiffness has a …. natural frequency
(stable sources)
higher
something with greater mass has a … natural frequency
(stable sources)
lower
stiffness increases and mass stays stable →vibrate frequency …
(stable sources)
increases
mass increases, stiffness stays the same → …frequency
(stable sources)
lower
dynamic sources have the capacity to change shape and/or tension
example: guitar strings
(dynamic sources)
directly proportional to tension…
when tension is increases, so is frequency
(dynamic sources)
inversely proportional to length and to cross section mass…
when length or mass is increases, frequency is lower
(dynamic sources)
length decreases → frequency
increases
(dynamic sources)
length and tension stay the same, cross sectional mass increases → frequency…
decreases
octave
the interval between two “notes”/keys where one is exactly one is exactly double the frequency of the other
semitone
one “step” in western musical scale, the difference in the frequencies between two adjacent piano keys
the relationship between Hz and “notes”/keys is …
logarithmic
pitch
perceptual correlate of frequency
if frequency increases, we perceive the pitch to…
increase
frequency is a … phenomenon, which can be measured
physical
pitch doesn’t have a unit, its …
psychological
if pitch goes up, frequency goes…
up
period
the elapsed time to complete one cycle of vibration
units: seconds/cycle
periodicity
the times per cycle is consistent
periodicity
the time per cycle is not consistent
period and frequency are
inversely proportional
shorter period: … frequency
higher
longer period: … frequency
lower
wavelength
the distance travelled by one cycle of vibration
wavelength refers to the cycle … whereas frequency and period refer to aspects of ……
distance
cycle time
wavelength formula
speed of sound = 331 m/s → speed of sound moves faster in higher temps
speed of sound is … underwater
faster
wavelength and frequency are ……
inversely proportional
wavelength and velocity …..
directionally proportional
wavelength increases, frequency…
decreases
wavelength increases velocity…
increases
Phase
the course of travel from a reference point
phase is
really important for sound
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
Interactive Interence
phase offset at 90 degrees
Interactive effect limited because of relative position to equilibrium
“it complicated”
Destructive Interference
signals 180 degrees out of phase
exactly the opposite of each other
flat line
Amplitude
degree if displacement/excursion from equilibrium within a vibratory cycle
reflects strength/magnitude/energy of wave
directionally proportional to its original force
Four Types of Amplitude
instantaneous
Peak/Maximum
Peak-to-peak
Root mean square (RMS)
instantaneous amplitude
amount of displacement at a particular point in time for phase angle
Peak Amplitude
furthest displacement from equilibrium (typically at a 90 degree angle)
Peak to Peak Amplitude
is the absolute difference between maximum positive and negative displacements
Root mean square amplitude
average amplitude all the way across the waveform
essentially the standard deviation of waveform
amplitude
amount of energy potential within a wave (volts)
energy
capacity to do work (joules)
power
rate at which energy is transferred/expanded (joules/second, watts)
intensity/sound pressure
flow of sound power through/over a given area
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
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
absolute measure
made directly and independently, single definitive wave
relative measure
context specific value in comparison to another wave
absolute measure of sound
definitive measure
relative measure of sound
comparison/ratio of the absolute power in one sound wave to another
sound amplitude is commonly reported in…
decibels
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
damping
the decrease in the amplitude of displacement over time
ordinate
y axis
vertical axis
intensity/power of sound
abscissa
x axis
horizontal axis
represented by time
Note
Flashcard