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7/23/2019 P2 - Ergo - Human Sensory System
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Human Sensory Sy
By : Dewi Hardiningtyas, ST, MT, M
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Illustrative
New warning sign
phone service have
on the Adirondack
drivers say they are
Whats your opinio
condition?
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Human beings receive stimuli from many sources. Some of t
be sensed, some cannot. The stimuli are distant or close so
energy, such as light, thermal energy, mechanical energy,
energy, sound, and so on.
Five classic sense (vision, audition, smell, taste, and touch),
EXTEROCEPTORS.These are so called since they deal wi
external to the body.
PROPRIOCEPTORSare stimulated by the actions of the bo
such as reach or a sudden turn. Proprioceptors are embedd
the subcutaneous tissue, such as in the muscles and tendon
the joints, and the inner ear.
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Wavelength
Amplitude Light is a wave of electrom
Amplitude perceived as br
Wavelength (nm) perceive
Eye is sensitive to the ligh
(The visible spectrum of electromagnetic energy / light)
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Types of color deficiencies and color
blindness :
Protanomaly(1% of males) low
sensitivity to red
Deuteranomaly(6% of males) low
sensitivity to green Protanopia (
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Source of light : candle
Luminous intensity / flux :
of the source (measured
12.57 lumins)
Illuminance : the amountstrikes the surface of a
(measured in units of10.76
Luminance : the amount o
objects to be detecte
recognized by the observe
not themselves the sourc
units of foot lamberts or c
Luminance is different fro
of differences in the amou
either reflect or absorb.
between black surface and
il(%)eReflectanc
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It is the ability to see fine detail /sharply.
The test can be done using Snellen EyeChart.
20/40 Vision a person can see from20 feet what a person with normal
vision can see from 40 feet 20/20 Vision a person can see from
20 feet what a person with normalvision can see from 20 feet
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In industrial tasks, where light
conditions change from light to dark,sufficient time must be allowed for darkadaptation.
Human Factors Application : why arered lights used in cockpits anddarkrooms?
Because rods are insensitive to thelongest wavelengths (red). It didnt
degrade dark adaptation.
When moving from dark to light ro
adapts in a few seconds.
But it takes up to 40 minutes to a
dark room.
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Spatial FrequencyLow High
100 %
0.5%
Contrast
Contrast, Spatial Frequenc
Font Style must be consider
text for optimum legibility
(Human Factors Application
background provides good
font size is highly legible, t
not allow for visual separatio
Spatial frequency is expressed as
the number of cycles per degree of visual angle.
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Variable Effect Example
Contrast Visibility Black print on gray
Illumination Contrast Sensitivity (CS) Reading map in poor ligh
Polarity Black on white better than
white on black
Designing viewgraphs
Spatial Frequency Optimum CS at 3 C/D Ideal size of text font giv
viewing distance
Visual Accommodation CS Map reading during night
Motion CS Reading a road sign while
moving
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Knowledge
Expectations
Desires
Perception
EXPERIENCE
STIMULUS
WORLD
The 5 senses
Top Down
Processing
Bottom - Up
Processing
is the visual ability to perceive the world in three dimen
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Linear Perspective : Parallel
lines appear to meet as they
travel into the distance.
DEPTH PERCEPTION
is the visual ability to perceive the world in three dimen
and the distance of an object.
MONOCULAR CUEScan be represented in just two dimensions and observed with jus
Relative Size : If two objects are roughly
the same size, the object that looks the
largest will be judged as being the closest
to the observer.
Interpositio
overlaps anot
partially obsbeing
is the visual ability to perceive the world in three dimen
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Light Shading - 3D objects
cast shadows and shade on
opposite side of illumination
source, and reflections on same
side
DEPTH PERCEPTION
is the visual ability to perceive the world in three dimen
and the distance of an object.
MONOCULAR CUEScan be represented in just two dimensions and observed with jus
Textual Gradients - Texture appears more
fine with increasing distanceAerial Perspective -
appear h
Motion Parallax - As
perceiver moves, objects
in foreground appear to
move by faster than
objects in background
is the visual ability to perceive the world in three dimen
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DEPTH PERCEPTION
is the visual ability to perceive the world in three dimen
and the distance of an object.
BINOCULAR CUESthat are based on the receipt of sensory information in three dimensions
Stereogram
3D
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O O O O O O O O
O O O X O O O O
O X O O O O O O
O O O O O O X O
O O O O O O O O
O O O O X O O O
Q Q Q Q Q Q Q Q
Q Q O Q Q Q Q Q
Q Q Q Q Q Q O Q
Q Q Q Q Q Q Q Q
Q Q Q O Q Q Q Q
Q Q Q Q O Q Q Q
Search time : T = (N x I) / 2
I = inspection time per object
N = total number of objects
Serial Search
Parallel Search
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Sound intensity (dB) = 20
where P2 is the thresho
Soundis the vibration of air mole
Amplitude - sound pressure perc
measured in decibels (dB)
Frequency- cycles per second (
pitch
1
2
3
Pressure
Time
Noise and vibration are both fluctuations in the pressure of air (or other media) which affect the
Vibrations that are detected by the human ear are classified as sound.
We use the term 'noise' to indicate unwanted sound.
Noise and vibration can harm workers when they occur at high levels, or continue for a long time
Try NOISE METER !
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T H E D E C I B E L S C A
Source
Jet at take-off; ear damage possible
Painful sound
Propeller plane at take-off
Loud thunder
Subway train
Truck or bus
Average auto, loud radio
Normal conversation
Quiet restaurant
Quiet office, household sounds
Whisper
Normal breathing
Threshold of hearing
P E R M I S I B L E N O I S E E X P O S U R E
Duration Intensity
8 hrs 90 dB
6 hrs 92 dB
4 hrs 95 dB
3 hrs 97 dB
2 hrs 100 dB
1.5 hrs 102 dB
1 hr 105 dB
0.5 hr 110 dB
< 0.25 hr 115 dB
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Outer ear converts sound energy to mechanical energy
(middle ear) to electrical nerve energy (inner ear), then
sends signal to the brain.
Pinnacollects sound, helps
glasses)
Tympanic Membrane (ear d
canal, vibrates to sound p
head) Ossiclesbones of middle e
to mechanical energy. Malleus (hammer) is the la
vibration from ear drum,
Incus (anvil), which is hinge
the Stapes (stirrups), whic
Window of the cochlea. Cochlea snail-like organ
energy is transduced to elect
way Hair Cells along the wav
that fire when they are b
Tectorial Membrane of the
sends a signal along the A
brain.
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Equal increases in sound intensity (on the decible sccreate equal increases in loudness; for example,
sound doesntsound twice as loud as a 40 dB sound
0
2
4
6
8
10
12
14
16
18
30 40 50 60
Intensity of 1000 Hz
Loudness
(sones)
1 sone = 40 dB tone of 1,000 Hz;
Loudness doubles with each 10
dB increase
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Loudness is affected by
sound frequency.
Humans are sensitive to
sounds between 20 Hz
and 20,000 Hz, but most
sensitive to 1,000 - 4,000Hz range.
All tones along a contour
are equally loud.
1 phon = perceived
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Criteria for good alarms:
1. Must be heard above background noise (app
above)
2. Avoid excessive intensity
Should not be above the danger level for hearing (85
Using a very different frequency may help (especiall
with criteria point 1)
3. Should not be too startling
4. Should not disrupt processing of other signals
- Do not want alarm to mask speech or other importa
5. Should be informative, not confusing
Sample Alarms
Is ea
Wha
Place mouse over each, do not click
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1. Conduct environment/task analysis must unders
sounds/noises (and their qualities) are associated
job
2. Make sure alarms are within humans cap
discrimination by varying on different dimensions: Pitch (low to high), Envelope (rising/falling pitch), Timb
and Rhythm (synchronous vs. asynchronous)
3. Design specific qualities of sound
For example : Use pulses to create unique sound
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Cry Wolf Syndrome Human operator fails to r
alarm due to the large number of false alarms in the To avoid CryWolf Syndrome:
Set the alarm criterion to be sensitive enough to minimwithout increasing false alarms.
May use more complex algorithms to determine true thr may use more than one signal measure
Train operators on the tradeoffs of false alarms/misses understand actual false alarm rates
Use multiple alert levels (denote different urgency state
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Speech com
measures:
Articulation Ind
up) signal to n
(speech dB
noise dB)
Higher frequenc
vulnerable to b
by noise
McGurk Effect is a perceptual phenomenon that demonstrates
an interaction between hearing and vision in speech perception.
The illusion occurs when the auditory component of one sound is
paired with the visual component of another sound, leading to
the perception of a third sound The visual information a person
gets from seeing a person speak changes the way they hear the
sound.
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Dangers of excessive noise:
Hearing loss
caused by exposure
to loud noises. Some hearing loss is
expected with age (higher freq.)
Loss of sensitivity
while noise is
present
Temporary Threshold Shift (TTS)
Loss of hearing that lingers after noise
is terminated (post-rock concert)
- Tinnitusor ringing in the ears
-
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Signal Enhancement increase the signal to noi
(make signal louder relative to background)
Noise Exposure Regulations OSHA standards b
Time Weighted Average (calculated with dosemeter)
if TWA > 85 dB (action level) employer must provid
protection if TWA > 90 dB (permissible exposure level) employer m
noise reduction measures
The SourceSelect equipment and tools that have
sound dampening
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Vestibular System which
contributes to balance in mostmammals and to the sense
of spatial orientation, is the sensory
system that provides the leading
contribution
about movement and sense of
balance.
Semicircular Canalsdetect angular acceleration (rotation) in 3 a crista embedded in a jelly-like material (cupola) is supported by hair c
and fire when the crista moves in response to head rotation.
Vestibular Sacs (Utricle Saccule)detect linear acceleration hair cells embedded in jelly-like substance lag behind when the head
motion becomes steady,otoliths
catch up and hairs no longer bent.
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Spatial Disorientationthe inability
to correctly interpret aircraft
attitude, altitude or airspeed, inrelation to the Earth or point of
reference, especially after a
reference point (e.g., the horizon)
has been lost.
Vection
- When a large pa
visual field moves, a viewer f
have moved and that the
stationary.
For example, when one is in a
station, and another neighbou
moves, one can have the illu
one's own train has move
opposite direction.
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Sopite Syndrome a neurological disorder th
symptoms of fatigue, drowsiness, and mood chprolonged periods of motion.
Subset of motion sickness symptoms, but sometime
manifestation
Dangerous because victims often not aware of its onlikelihood of onset
Found to affect passengers and operators of cars, tr
helicopters, planes, and simulators
No known prevention techniques (many motion
medications increase drowsiness)
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TactileCutaneous or somatosensory sense provid
receptors just under the skin.
Types of Receptors:
Thermoreceptors detect heat/cold
Mechanoreceptors detect pressure
Nociceptors detect noxious stimuli (caustic substance
HapticShape information provided through manip
fingers
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Haptic technology, or haptics, is a
feedback technology which takes advantage of the stouch by applying forces, vibrations, or motions to th This mechanical stimulation can be used to assist in the
of virtual objects in a computer simulation, to control suobjects, and to enhance the remote control of mach
devices (telerobotics). It has been described as "doing for the sense of tou
computer graphics does for vision".
Haptic devices may incorporate tactile sensors that forces exerted by the user on the interface.
Tactile haptic feedback is becoming common in
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