Exam 1

for 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