Hearing Science Test 2

Front 1

Complex Wave

Back 1

any sound wave that isn’t sinusoidal

Front 2

Fourier Series

Back 2

series of sine waves that are combined to compose a complex periodic wave

Front 3

Fourier Analysis

Back 3

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

Front 4

Periodic Wave

Back 4

wave that repeats itself at regular intervals over time

Front 5

Harmonic Series

Back 5

the series of frequencies in a harmonic relation

Front 6

Harmonic Relation

Back 6

a. Frequencies of all of the sinusoids that compose the series must be integer (whole #) multiples of the lowest frequency component in the series

Front 7

harmonics

Back 7

each component of a harmonic series

Front 8

Fundamental Frequency

Back 8

the very first harmonic in a harmonic series

Front 9

Designation of Partials

Back 9

1st partial = 1st harmonic
2nd partial= 2nd harmonic

Front 10

Designation of Overtones

Back 10

1st overtone= 2nd harmonic
2nd overtone= 3rd harmonic

Front 11

Aperiodic Wave

Back 11

a wave that doesn’t have periodicity; Vibratory motion is random, thus vibratory motions are called random time functions; With an aperiodic wave, there are no two regions that are the same region they don’t repeat
They can maintain many frequencies

Front 12

Amplitude Spectrum

Back 12

shows amplitude (in either relative or absolute values) as a function of frequency

Front 13

Octave

Back 13

a doubling or halving of frequency; Refers to a frequency of 2:1 or 1:2

Front 14

Line spectra

Back 14

Spectra that shows frequency at horizontal ine & amplitude at vertical line. Energy is present only at frequencies represented by vertical lines. There is no energy at frequencies b/t two adjacent components

Front 15

Continuous spectra

Back 15

energy is present at all frequencies between certain lower and upper frequency limits

Front 16

Phase Spectrum

Back 16

defines the starting phase as a function of frequency

Front 17

Sawtoothed Wave

Back 17

1. A complex periodic wave with energy at all odd and even integer multiples of the fundamental frequency
2. a. Amplitudes decrease as inverse of harmonic number
3. db= -20log10 hi
4.Slope of envelope of square wave is also -6db per octave

Front 18

Square Wave

Back 18

1.A complex wave with energy only at odd integer multiples of the fundamental frequency
2. Amplitudes decrease as the inverse of the harmonic number
3.Slope of envelope of square wave is also -6db per octave
4. db= -20log10 hi

Front 19

Triangular Wave

Back 19

1.A complex wave with energy only at odd integer multiples of the fundamental frequency

2.Amplitudes of sinusoidal components decrease as the reciprocal of the square of the harmonic.

3.dB=-40log10hi

4.Slope= -12 db per octave

Front 20

White Noise

Back 20

1. aperiodic waveform with equal energy within any frequency band 1 Hz wide (from f -.5 Hz to f +.5 Hz) and with all phases present in a random array

Front 21

Amplitude spectrum of white noise

Back 21

continuous spectrum
a. White noise has same amount of energy in every frequency band that is 1 Hz wide regardless of the value of f.

Front 22

Signal-to-Noise Ratio

Back 22

1. the relation between signal level and noise level
2. A positive S/N ratio means signal level exceeds noise level
3.A negative S/N ration means noise level exceeds signal level
4.A S/N ratio of 0 dB means that noise and signal level equal each other
5.When dB subtract noise from sound because law log 2 if division 10log(S/N)

Front 23

Nulls

Back 23

Regions of 0 energy; occur at the reciprocal of the pulse duration

Front 24

Pulse Train

Back 24

a repetitious series of rectangular shaped “PULSES” of some width or duration (Pd) that occurs at a regular rate.

Front 25

How do we calculate the frequency of the pulse train?

Back 25

1/T`

Front 26

Nulls

Back 26

Regions of 0 energy that occur at the reciprocal of the pulse duration 1/2 ms (500 hz), 2/2 ms (1000 hz), 3/2 ms (1500 hz)

Front 27

Principle of Resonance

Back 27

When a vibrating source (the tuning fork) is applied to an elastic system (the table),the elastic system will be forced to initially vibrate at the frequency of the applied force

Front 28

Principle of Resonance as applied to frequency & amplitude

Back 28

The closer the freq of the applied force to the natural frequency of the elastic system, the greater the resulting amp of vibration

Front 29

Natural frequency or resonant frequency (fnat or fc)

Back 29

the point at which the elastic system reaches its greatest amplitude of vibration

Front 30

dB level of natural frequency

Back 30

0db

Front 31

What happens after the frequency surpasses the natural frequency?

Back 31

the amplitude of vibration begins to diminish in a manner that is symmetric with the increase that was observed before the system reached its natural frequency

Front 32

What determines the natural frequency?

Back 32

mass and stiffness

Front 33

When is the amplitude of vibration of the elastic system greatest?

Back 33

When the driving frequency equals the natural frequency of the system

Front 34

a system that responds differentially or selectively as a function of frequency

Back 34

Frequency selective system

Front 35

What are the two components of impedance (Z)?

Back 35

Resistance (R)
Reactance (X)

Front 36

Resistance

Back 36

energy dissipating; independent of frequency

Front 37

Reactance

Back 37

energy storing; frequency dependent

Front 38

Two types of reactance

Back 38

mass reactance and stiffness (compliant) reactance

Front 39

Mass reactance (Xm)

Back 39

directly proportional to frequency --> increases as frequency increases

Front 40

Compliant reactance (Xc)

Back 40

inversely proportional to frequency --> decreases as frequency increases

Front 41

Natural frequency in relation to reactance

Back 41

At Fc, Xm = Xc

Front 42

Formula for total impedance

Back 42

Z=√(R^2+ (xm-xc)^2 )

Front 43

What is acoustic impedance

Back 43

The total opposition to motion

Front 44

Stiffness dominance

Back 44

1. For frequencies below the natural frequencies, stiffness is dominant.
2. Stiffness reduces low frequency energy
3. amplitude of vibration decreases
4. impedance increases
5. Xc = 1/2 pi * Fc

Front 45

Mass dominance

Back 45

1. For frequencies above the natural frequency, mass is dominant.
2. Mass reduces high frequency energy
3. amplitdue of vibration decreases.
4. impedance decreases.
6. Xm= 2piFm

Front 46

What would happen to the curve if no resistance was present?

Back 46

maximum transfer of energy would occur and the response of the system at the natural frequency would be infinite

Front 47

What happens as resistance increases?

Back 47

more energy is dissipated, damping increases and the system becomes more broadly tuned

Front 48

What happens as resistance decreases?

Back 48

the system becomes less damped and more narrowly tuned

Front 49

Admittance

Back 49

Energy admitted to a system

Front 50

When does the highest amount of admittance occur?

Back 50

When driving freq= natural freq more energy is accepted by or admitted to the elastic system

Front 51

Relation of Admittance to Impedance

Back 51

Admittance is inversely proportional to Impedance

Front 52

Units of measurement for Impedance & Admittance

Back 52

Impedance= ohm
Admittance= mho

Front 53

Characteristics of a narrowly tuned system

Back 53

i. Minimal resistance
ii. Little damping
iii. Allows free vibrations to continue for considerable amounts of time
iv. Efficient generators of sound

Front 54

characteristics of a broadly tuned system

Back 54

i. Higher resistance
ii. Higher damping
iii. Free vibrations that last for a brief duration of time
iv. Efficient transducers- convert energy from one form to another