speech + hearing sci exam 1

pressure

-quantity constituted by size of area over which force is applied
-p = F/A
-unit: N/m^2 = pascal (Pa)
-cgs unit: dynes/cm^2

work

-occurs when force applied to body results in its displacement
-W = Fx
-mks unit: joule (J)
>amt of work that occurs when 1 N of force affects 1 m of displacement
-cgs unit: erg (dyne x m)

potential energy

capability of body at rest to do work

kinetic energy

capability of body in motion to do work

power

-rate at which work is done
-P = W/t
-P = Fv
-unit: watt (W) (same in cgs)

intensity

-develops when power is dist over area
-I = P/A
-mks unit: W/m^2
-cgs unit: W/cm^2

inverse square law

-intensity decreases w increasing distance from sound source
-amt of intensity drops by 1 over square of change in distance

acoustics

sci of sound

3 basic phys quantities

mass (g/kg), time (s), length (cm/m)

mks vs cgs

mks uses kg + m, cgs uses g + cm 

scalar vs vector quantity

Scalars can be fully described by their magnitudes while vectors have direction + magnitude

displacement (x)

quantity that includes magnitude + direction

avg velocity

-distance traveled divided by time it took to make trip

-v = (x2-x1)/(t2-t1)

instantaneous velocity

-velocity of body at given moment

-v = dx/dt

avg acceleration

-diff btwn 2 velocities divided by time interval 

-a = (v2-v1)/(t2-t1)

-unit: m/s^2 (mks) + cm/s^2 (cgs)

instantaneous acceleration

-acceleration at given moment

-a = dv/dt

force

-outside influence that makes stationary object move or causes moving object to change speed/direction

-F = Ma

-unit: newton (N) = 1 kg x 1 m/s^2 (force needed to cause 1 kg mass to accelerate by 1 m/s^2)

-dyne in cgs

momentum (Mv)

quantity of motion of moving body

resistance/friction

-force that opposes motion

-constituted by sliding of one body on another

-Ff = Rv

-Ff  = force of friction

-R = coefficient of friction btwn materials

-v = velocity of the motion

elasticity

property whereby deformed object returns to its original form

restoring force

-force that opposes deformation of an elastic/spring-like material 

-F_R = Sx

vibration

oscillation of an object

sound

form of vibration thats transferred from air particle to air particle in form of wave

cycle

1 complete round trip of an oscillating motion

frequency

number of cycles that occur in 1s

damping

dying out of vibrations over time

waveform

graph that shows displacement (or another measure of magnitude) as function of time

ambient/atmospheric state of air pressure

pressure that exists among air molecules that arent being disturbed by a driving force

compression state of air pressure

increase in air pressure relative to ambient pressure among undisturbed molecules when disturbed air molecules are forced together

rarefaction state of air pressure

state of lower than ambient pressure

pure tones

sounds associated w simple harmonic motion

transverse wave type

wave made when particles move at right angles to direction that wave is propagating

longitudinal wave type

wave made when each air particle oscillates in same direction that wave is propagating

sinusoidal wave type

simple harmonic motion

phase

relationship btwn 2 waves that are displaced relative to each other

what makes sound wave periodic?

repeats itself exactly over time

period (t)

-duration of 1 cycle
-expressed in time

frequency (f)

-number of cycles that can fit into 1 s
-unit: Hz
-f = 1/t

peak-to-peak amplitude

total vertical distance btwn (+) + (-) peaks

instantaneous amplitude

magnitude of sound at given moment

root-mean-square (rms) amplitude

found by squaring all (+) + (-) values, finding mean, rescaled by finding sqrt

wavelength (λ)

-distance covered by 1 cycle of propagating wave
-c/f
-c: speed of sound (344 m/s)

how do frequency, period, wavelength relate to each other?

y + f are inversely proportional to each other, f + t are reciprocals of each other

complex wave

when 2/> pure tones are combined

aperiodic wave

waveform doesnt repeat itself over time

how sine waves are added

at every point along x axis: find amplitude of each wave at that point in (+) + (-) directions, add the 2 amplitudes algebraically, plot sum along same point on x axis, draw line thru all points after doing this for many points

reinforcement

when combined wave has amplitude increase

cancellation

when combined wave has amplitude decrease

fundamental frequency (f1)

lowest frequency component of complex periodic wave

harmonics

whole number or integral multiples of f1

spectrum shows ? as function of ?

amplitude; frequency

goal of fourier analysis

to mathematically dissect complex sounds into their pure tone components

aperiodic sounds

-made up of components that arent harmonically related
-have waveforms that dont repeat themselves

transient

abrupt sound thats extremely brief

white noise

contains all possible frequencies

what are continuous spectrums usually used for?

aperiodic sounds

spectrum for random noise

flat + continuous

spectrum for transient noise

flat

natural/resonant frequencies

frequencies at which body vibrates most readily

standing waves

-pattern that appears standing still even tho its derived from interaction of propagating waves
-comes from waves reflecting back + forth and superimposing on each other

nodes

places along string/medium where theres 0 displacement in standing wave pattern

antinodes

places where max displacement occurs in standing wave pattern

1st mode

-longest standing wave pattern
-half of wavelength

vibration in tubes

-shorter tubes have higher pitches
-higher pitch when open at both ends

vibration in tubes open at both ends

-least particle displacement in center (where pressure is highest)
-highest displacement at ends
-1st mode

vibration in tubes open at 1 end

-particles most restricted at closed end
-pattern corresponds to 1/4 of wavelength

half + quarter-length wavelengths differences

-f = c/2L vs c/4L
-all vs odd modes
-all vs odd harmonics produced

3 ways to measure amplitude

peak, peak-to-peak, rms

immittance

gen term used to describe how well energy flows thru system

impedance (Z)

-opposition to energy flow
-unit: ohms (omega)
-Z = F/v

admittance (Y)

-ease w which energy flows thru system (impedance inverse)
-unit: mho (ohm inverse)

3 phys components that interact during impedance

mass, stiffness, friction

Mass (positive) reactance (X_m)

-opposition to energy flow due to mass (inertia)

-Xm = 2(pi)fM

Stiffness (negative) reactance (X_s)

-opposition of energy flow due to stiffness
-Xs = s/2(pi)f

net reaction (X_net) formula

Xs/Xm - Xm/Xs (bigger one goes 1st)

conductance (G)

-reciprocal of resistance
-G = 1/R

stiffness (compliance) susceptance (B_s)

-reciprocal of stiffness reactance
-Bs = 1/Xs

susceptance (Bm)

-reciprocal of mass reactance
-Bm = 1/Xm

acoustic immittance

opposition to sound energy flow but uses sound pressure + volume velocity

acoustic impedance (Za)

-opposition to sound energy flow
-Za = p/U = sqrt(Ra^2 + Xa^2)
-p = sound pressure
-U = volume velocity

acoustic admittance (Ya)

reciprocal of acoustic impedance

acoustic resistance (Ra)

friction that develops btwn air molecules + mesh screen

Mass (positive) acoustic reactance (+X_a)

mass reactance is out of phase w resistance (velocity lags the pressure)

Stiffness (negative) acoustic reactance (-X_a)

-sound pressure compresses air column like spring
-negative bc reps restoring force

what do dB measure

ratios btwn phys magnitudes

reference point sig

-range of sound magnitudes is huge
-dB convert abs phys values into simpler forms using ratios + logs

reference value

-denominator of ratio used to calculate dB
-softest sound normal ppl can hear

sound level meter (slm)

device that measures sound magnitude

z-weighting

-no weighting or unweighted
-displays overall spl based on all sounds picked up
-no adjustments made
-sound levels at all frequencies treated exactly as picked up
-dB SPL or dBZ
-barely diff from flat, unweighted response

a-weighting

-most common in ansi standard for slms
-considerably de-emphasizes low frequencies
-gets more negative as frequency decreases < 1k Hz
-dBA

b-weighting

-de-emphasizes lower frequencies but not as much as a
-only ~6 dB of reduction at 100 Hz
-dBB
-rarely used + no longer included in ansi standard for slms

c-weighting

-commonly used as proxy for fully flat (z) response
-dBC

octave-band filter

-allows slm to look at certain range of frequencies
-separates overall frequency range into narrower ranges
-each range = 1 octave