Hearing Science

Front 1

Fourier analysis

Back 1

a complex waveform can be decomposed or analyzed to determine the amplitudes, frequencies, and phases of the sinusoidal components

Front 2

periodic wave

Back 2

repeats itself at regular intervals over time (complex)

Front 3

complex wave

Back 3

sinusoid than can differn in amplitude, freqency and phase

Front 4

harmonic relation

Back 4

frequencies of all the sinusoids that compose the series must be integer multiples of the lowest frequency component

Front 5

fundamental frequency

Back 5

first harmonic

Front 6

sawtooth wave

Back 6

odd and even whole number multiples of the fundamental frequency

Front 7

Time domain

Back 7

instantaneous amplitude over time, amplitude is Y axis, Time is X

Front 8

Freqency Domain

Back 8

requires amplitude and phase graph, amplitude most imp, phase req. for completeness, time is discarded

Front 9

square wave

Back 9

all odd harmonics

Front 10

Phase

Back 10

In Phase- same form, diff heights
90 out of phase- diff heights
180- cancel

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triangular

Back 11

odd integer multiples, decrease 12 dB per octave

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octave

Back 12

doubling of halving of frequency

Front 13

white noise

Back 13

equal energy within any frequency band 1 Hz wide and with all phases in a random array

Front 14

Transient signals

Back 14

increase duration of signal, gradual rise and fall (more frequency specific)

Front 15

pulse duration

Back 15

null scores occurs at integer multiples of the reciprocal of the pulse duration

Front 16

Resonance Principle

Back 16

when a periodicallt vibrating force is applied to an elastic system, the elastic system will be forced to vibrate initially at the frequency of the applied force, the nearer the frequency of the applied force to the natural frequency, the greater the amplitude of vibration will be

Front 17

forced vibration

Back 17

vibration of one object causes another object to vibrate

Front 18

natural frequency

Back 18

proportional to stiffness
inversly to mass

Front 19

resonator

Back 19

object that is vibrating in response to some driving force (enhancing sound or enhancing frequency near objects resonant frequency)

Front 20

MAX AMPLITUDE

Back 20

when an object is forced to vibrate maximally with the driving force corresponding to the objects natural frequency

Front 21

2 resonators

Back 21

mechanical- tuning fork, stereo
acoustical(contains air)- guitar, bottle, jar
the mass and stiffness change if different frequencies are produced

Front 22

Helmholtz resonators

Back 22

developed glass globe with hold in each end, had people put wax in one ear and on end of globe and had people speak into it
**implications for speech- we are system of air filled cavities if we change the shape of thses, resonate frequencies will change
**hearing- ear canal is resonator, it enhances sound

Front 23

Amplitudes of vibration

Back 23

are less for frequencies that are either lower or higher than the natural frequency

Front 24

impedence

Back 24

the greatest amplitude of vibration occurs at the natural frequency because that is the frequency at which the least impedence is encountered

Front 25

Reactance Forms-
Mass Reactance

Back 25

directly proportional to frequency
2(pie) fm=

Front 26

Reactance Forms- Stiffness Reactance

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inversly proportionall
1/2(pie)Fs

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Resistance

Back 27

as resistance increases, more energy is dissipated, damping increases and the system is broadly tuned
=disipated energy (due to frictional forces) independent of frequency

Front 28

broadly tuned system

Back 28

can be forced to vibrate with max amplitude by external forces over a wide range of frequencies, no ringing
=high resistance, high damping
good transducers of sound

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narrow tuned

Back 29

reach peak amp. at narrow range and takes a long time to die out, repsonds max. at a few frequencies
=minimal resistance, little damping

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damping

Back 30

amp. decreases over time

Front 31

pink noise

Back 31

spectrum level decrease and frequency increases, octave band slope=0

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impedence matching

Back 32

at natural frequency, impedence is minimal and admittance is maximal
we want output impedence to match input impedence for max. transfer of energy

Front 33

natural freqency is greatest when

Back 33

mass reactance =stiffness reactance

Front 34

5 parameters of a filter

Back 34

natural frequency, upper cutoff frequency, lower cutoff frequency, bandwidth, rejection rate

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natural frequency

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frequency that will result in max. amplitude of vibration

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low pass filter

Back 36

passes energy below some designated upper cutoff

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high pass filter

Back 37

passes energy above some desig. lower cutoff

Front 38

bandwidth

Back 38

fU-FL
width of band of frequencies between the lower and upper cutoff frequencies, and it defines the range of frequencies over which energy is passed by the filter
= INDEPENDENT of the center frequency

Front 39

reactance

Back 39

stored energy, frequency DEPENDENT

Front 40

analog to digital conversion

Back 40

analog signal digitized by sampling signal at certain intervals, more we sample more accurate the representation
digital-ideal

Front 41

constant percentage bandwidth filter

Back 41

bandwidth NOT indepenedent of center frequency
* .707
geometric mean of center frequency square root of fU * fL

Front 42

Resonance of Cavities

Back 42

-large cavity- low frequency
-small area, lower frequency
-diferent constrictions of diff. cavities produce diff sounds

Front 43

one quarter wave resonator

Back 43

wavelength of lowest resonant frequency that will yield a max. amplitude is 4x length of tube
vocal tract-tube closed at one end and open at other