p2 - ergo - human sensory system

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


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



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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



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



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DEPTH PERCEPTION



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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p2 - ergo - human sensory system

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