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AUDE 5450 AMP 1 > Exam 2: Amplifiers & Compressors > Flashcards

Exam 2: Amplifiers & Compressors Flashcards

1
Q

pre-amp

A

FET

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2
Q

final amplifier

A

output amplifier

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3
Q

what is field effect transistor

A

pre-amp
takes the analog electric signal and adds amplitude to make it bigger and easier to go through the rest of the components

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4
Q

what is transistor based amplifiers

A

there are multiple throughout the ha
past pre amp but before vc
adds gain to input signal in order to increase the amplitude of the electrical signal

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5
Q

what is output amplifier

A

additional gain added at output level for max output to arrive to the receiver that will be transitioned to the acoustic signal

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6
Q

What is an input/output curve (I/O)

A

chart showing intensity of input compared to output at the TM

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7
Q

I/O axis representation

A

x axis is db SPL representing the input signal
y axis is db SPL representing output arriving to ™

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8
Q

what is linear amplification

A

adds same gain to all inputs

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9
Q

uses 1:1 compression ratio

A

linear

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10
Q

what is meant by 1:1 compression ratio

A

for every 1 spl increase in input, 1 spl increase in output occurs until max output is reached

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11
Q

Cochlear damage causes __________ perception

A

abnormal loudness growth

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12
Q

does linear amplification restore normal loudness growth

A

no
takes all sounds and adds the same gain

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13
Q

why doesn’t linear restore abnormal loudness growth

A

because it applies same gain at all inputs so they have some signals underamplified and other signals that are overamplified

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14
Q

what is a compressor/compression

A

level detector
used to fit amplified signals into reduced dynamic range
when an input gets loud compressor automatically kicks in and compresses the signal adding less gain to it
provides nonlinear amplification

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15
Q

aka automatic gain control

A

compression/compressor

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16
Q

provides nonlinear amplification

A

compressor/compression

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17
Q

what is compression ratio

A

determines how much gain is added to the input signal

refers to that for every increase of x dB how much output will you get

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18
Q

what controls affect compression

A

Threshold kneepoint (TK)
Attack time
Release time
Compression ratio

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19
Q

when level detectors & compressor are activated at pre amplifier before volume control

A

AGCI-I

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20
Q

when level detector is associated with output compressor, after volume control

A

AGC-0

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21
Q

what is threshold kneepoint

A

changing from 1 compression ratio to another
point at which slope of I/O fxn changes

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22
Q

what is a high TK

A

> /= 85 dB SPL

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23
Q

what is a high tk used for

A

to limit ha output so it doesn’t exceed individuals LDL

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24
Q

what is a low tk

A

</= 50dB SPL

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25
Q

what is a low tk used for

A

to improve audibility of softer speech components

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26
Q

what is attack time

A

time that it takes a compressor to turn on when the input is loud enough

hwo long it takes compressor to kick in full gain reduction after exceeding threshold

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27
Q

overshoot

A

fast attack time

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28
Q

sudden loud sounds

A

fast at

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29
Q

speech signals

A

slow attack time

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30
Q

what is overshoot

A

period of over amplification

output signal overshoots targeted SPL

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31
Q

what is release time

A

time it takes for compressor to deactivate when level falls below TK

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32
Q

undershoot

A

release time

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33
Q

what is undershoot

A

output signal undershoots targeted SPL
period of under amplification

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34
Q

what are the pros of fast compression (fast at/rt)

A

better for sudden loud sounds
soft sounds remain audible following RT
consonants stay audible after loud vowel sounds following RT

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35
Q

what are cons of fast compression (fast at/rt)

A

speech envope changes so what you are used to hearing and understanding is altered and the brain know longer recognizes the signal that is stored
uses more working memory because auditory memory has changed

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36
Q

what do PT’s with low cognitive abilities benefit from

A

slower at’s

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37
Q

what population wears HA’s? what population can experience cognitive decline?

A

geriatrics
a lot prefer slow acting because it keeps spectral env and easier to match the signal to their auditory memory

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38
Q

pros of slow compression (slow at/rt)

A

keeps original spectral envelope for easier processing in those with poor working memory or severe HL

promotes naturalness of sound

listening effort decreases

ILD preserved bw ears

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39
Q

cons of slow compression

A

sudden loud sound attenuates output signal during conversation making speech briefly inaudible

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40
Q

best suited for sudden loud sounds to maintain comfort, and avoid auditory damage

A

fast attack

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41
Q

best for conversational speech to maintain the shape of the spectral envelope

A

slow attack

42
Q

depends on the intensity & duration of an activating signals.

A

release time

43
Q

brief, intense sounds (such as a door slamming)

A

fast release time because uncompresses quick to maintain speech signals following

44
Q

longer intense sounds (such as a raised voice)

A

longer release time because it maintains a comfy output level during brief gaps of silence

45
Q

yelling (at/rt)

A

fast attack, slow release

46
Q

what is a compression ratio

A

how much compression to apply

how much gain to add to the input signal

47
Q

what is harmonic distortion

A

frequency components that are added to a HA output that wasn’t in the input signal

48
Q

what results in an amplified signal results in a distorted output signal

A

aggressive clipping

49
Q

what is a bill circuit

A

bass increase at low level circuit
in noisy environments >50dB LF output is reduced to limit loudness of noise to improve understanding in noise

50
Q

what does cutting LF gain sound like

A

tinny and harsh

51
Q

what are till circuits

A

HF gain increases when overall input is quiet to help audibility of soft sounds in QUIET

52
Q

what is a kamp circuit

A

most common till still used today
musicians love this because it doesn’t change shape of the sine wave & lets loud sounds through with no distortion and makes signal more clear
as input level increases the responses flatten

53
Q

what are the types of compression

A

expansion, WDRC, OLC

54
Q

whenever there is a change

A

TK

55
Q

what is the purpose of output limiting compression

A

compression is applied to loud output signals in order to protect the ear from over amplified sounds

56
Q

what are the benefits of OLC

A

reduces but doesn’t limit distortion
maintains output intensity below LDL
stops the risk of NIHL

57
Q

Only peak clipping result in distortion and loss of acoustic detail, but OLC distortion is less noticeable

A

false, they both result in distortion

58
Q

Helped loudness tolerance in linear devices but didn’t restore audibility of soft input signals or normal loudness perception

A

OLC

59
Q

what is maximum power output (MPO)

A

devices loudest ouput it can produce no matter the input level

60
Q

what is peak clipping

A

happens when signal exceeds threshold
form of compression
stops output increase aggressively and clips the amplitude once the signal’s intensity reaches the circuit max

61
Q

what is WDRC theory

A

soft input needs more gain than intense sounds

frequency response should change with varying input levels

62
Q

how does WDRC restore loudness growth function of HI PT

A

the low CR in WDRC shapes sound into dynamic range adding gain at low TK to improve soft sound audibility

it adds more gain to soft sounds and less gain to loud sounds allowing for more access to sound before output reaches LDL

63
Q

why does linear amplification not restore loudness growth function

A

because it adds the same gain for every input resulting in under amplified and over amplified sounds

64
Q

Explain how raising/lowering a TK input level alters the output of signals at or below the TK.

A

shifting TK lower increases output for soft signals at or below TK
raising TK decreases output for soft signals

65
Q

as TK is lowered output signals increase

A

WDRC improves audibility of soft consonant sounds
OLC applies increased CR to loud input signals earlier for increased comfort

66
Q

as TK is raised output signals decrease

A

reduces audbility of soft LF background noise
increases device MPO when PT can tolerate greater output of loud input signals to improve clarity

67
Q

if a PT needs more clarity of consonant sounds

A

shift tk down

68
Q

Bob can actually hear and perceive soft sounds as being soft; he likes them and wants to hear all of them. They make sense to him and enrich his hearing experience. How would you shift TK

A

lower it

69
Q

Sam has difficulties coping with all the soft sounds in his environment, which he tends to describe as “noise” rather than sound. He has difficulties making sense of these soft sounds.
how would you shift TK

A

raise tk

70
Q

as input increases amount of gain applied is reduced

A

compression

71
Q

as input increases amount of gain applied is rapidly increasing

A

expansion

72
Q

let’s HA sound silent when in quiet environments

A

expansion

73
Q

Differentiate AGC-o from AGC-i based on their location, function, and associated types of compression

A

o- after vc, at the output level, manages loud sounds and compresses them before going into the PT’s ear, OLC >/= 80 dB SPL

i - before VC, manages incoming sound, compresses at pre-amplifer when input is louder than TK
b/w 20-50 dB SPL (WDRC)

74
Q

when do we use expansion

A

when someone complains about soft sounds they find annoying and do not need to hear

75
Q

location, TK, CR of expansion

A

0-20 dB input
really low CR; lower than linear (1:1)
</= 0.9:1

76
Q

when is WDRC used

A

use this when soft sounds need to get louder and need to expand dynamic range

input compression, before the volume control
activates at the pre-amplifier, when input is louder than low TK

aka AGC-i

77
Q

location, TK, CR, AT/RT of WDRC

A

before vc/preamplifier
TK bw 20-50 dB
CR bw 1.1-4.1 (LOW cr; almost linear)
slow AT/RT

78
Q

how does WDRC work

A

a lot of gain is added to soft signals for audibility, minimal gain is added to moderate sounds and even less gain is added to loud sounds

79
Q

why do we want slow at/rt in wdrc

A

slow at: preserves temporal envelope of speech signal
slow rt: reduces inaudibility time of soft consonant sounds after compression release

80
Q

restores loudness perception

A

WDRC

81
Q

when do we need OLC

A

needed for loud sounds to protect the ear

AGC-o

limits MPO so HA doesn’t exceed LDL

82
Q

location, tk, at/rt/ cr of OLC

A

engages AFTER VC
tk: >/= 80dB SPL
high cr: >/= 5:1
AT: fast to protect ear from loud sounds
RT variable (fast = sudden noises, slow = sustained loud noises)

83
Q

which mic has the best DI

A

hypercartiod

84
Q

what is DI of hypercartiod

A

6.0 dB SNR

85
Q

what is DI of supercartiod

A

5.7 dB SNR

86
Q

what is DI of cartiod

A

4.8 dB SNR

87
Q

DI of omnidirectional

A

0 dB SNR

88
Q

what have we learned so far

A

Sound comes into mic (either in or out of phase; in goes on out is nulled), MEMS or ECM mic transduces acoustic signal by compressing and decompressing the diaphragm and the backplate creating the + and - analog electrical signal
Went from carbon balls, to piezoelectric now to MEMS or ECM
MEMS is better - used for PT who needs durable, rigorous HA; used for construction worker who is outside and sweats all day or someone who lives in humid environment like florida or new orleans, or even someone who leaves their HA in their car MCM - less durable & more susceptible to heat & humidity; grandma that lives in assisted living
NOW, sound leaves mic and goes through a bunch of circuits that either compress or amplify the signal
Signal is either amplified (transistor) or compressed (resistor) and is either routed to AGC-i or AGC-o
Either amp or level detector determines if sound needs to be compressed (detecting how loud it is)
AGC - i: electric signal comes in and either goes on or is compressed
AGC-o: goes through all DSP and out on other side of VC and either is amplified or compressed by OLC
Then sound goes to the receiver to be transduced back to an analog acoustic signal

89
Q

what is slow acting compression good for

A

good for those with lower cognitive capacity because temporal envelope is not compressed and looks more like what our brain stored of the sounds; while someone speaks, amp of temporal envelope shape is closer to auditory memory of signal for longer periods of time

90
Q

what is fast acting compression good for

A

gets compressed, work harder to match sound is sort of a memory to understand and causes more listening effort resulting; doesn’t take a lot of volume for it to compress & envelope doesn’t look like memory of it working harder to understand what was said

91
Q

fast AT slow RT

A

Loud sustained sound
do not want the pumping of compressors turning on and off

92
Q

fast AT/RT

A

loud sudden sound

93
Q

fast release

A

abrupt vowel sound like laughing in the middle of talking

94
Q

what is a frequency shaping band

A

frequency response is a series of VC called bands/handles
VC’s that separate individual frequency ranges, doesn’t change CR, adds gain equally for soft, moderate and loud input signals
ROWS

95
Q

what is compression shaping channels

A

COLUMNS
shape compression characteristics into individuals dynamic range

96
Q

what settings are adjusted in compression shaping channels

A

expansion threshold tk wdrc cr olc and they all vary by frequency

97
Q

what do contemporary devices have

A

multiple TK’s with different CR within a frequency range

98
Q

how can you maximize speech intelliginility in contemporary HA’s

A

multichannel wdrc

99
Q

what does multichannel wdrc do

A

vary expansion - reduces low level noise present in any channel

vary tk - enahcne speech signal present in any channel

vary CR - optimize dynamic range in any channel

vary MPO - for tolerance within different frequency ranges

100
Q

what is curvilinear compression

A

CR increases as input increases creating the curvilinear shape

AUDE 5450 AMP 1 (9 decks)

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