Ear

Question 1

Arrangement of the Ear

Answer 1

• Auditory system (hearing)
  
  • Vestibular system (balance)

Question 2

Auditory system
(Outer Ear)

Answer 2

1. Air pressure waves gather at the outer ear, where the Pinna is.
   
   2. The Pinna is our outer ear cartilage that alters sound helps us determine where it’s coming from
   3. The air pressure waves pass through the out ear canal / auditory canal till the ear drums
   4. The waves create vibration at the Ear drum membrane

Question 3

Middle Ear

Answer 3

5. The vibration (mechanical energy) is transferred by 3 bones (Malleus, Incus and Stapes)
   
   6. Those 3 bones that the vibrations are passing through are in an ‘Air filled’ middle ear and are converted to mechanical energy
   7. Vibrations are passed to the Oval Window membrane & Round Window membranes
   8. Oval Window separates Air middle ear from Liquid Inner ear
   9. The vibration in oval window get set up as pressure waves

Question 4

Inner Ear

Answer 4

10. Pressure waves travel through liquid inner ear/ Cochlea
11. Cochlea is split into 3 chambers by membranes
12. The pressure waves in the guilt set up a patter of waves in the Basilar Membrane
13. Different frequencies produce different vibrations along the basilar membrane
    High frequency cause a peak near the Round Membrane
    Low frequency cause a peak near the end of Cochlea
14. Hair like sensors in the Basilar membrane translate membrane movement into electrical signals to the brain via auditory nerve

Question 5

Equalization of the ear

Answer 5

when air pressure in middle ear and outer ear (either side of ear drum) are equal
The pressure between the middle ear and atmospheric need to be equalised.

Question 6

what is the name of the tube that helps with ear equalization

Answer 6

Eustachian tube

Question 7

Explain how it works

Answer 7

The tube is a like a one way valve

it connect middle ear cavity to the back of the nose

it allows air flow from middle ear out to release pressure.

when you swallow, the flows out the tube.

Question 8

Air pressure when ascending

Answer 8

the pressure in the middle ear is higher than outside, so the air pressure is released from the middle ear via Eustachian tube via swallowing

Question 9

Air pressure when descending

Answer 9

pressure is lower in the middle ear than outside

however the eustachian tube in just one way valve, so this can cause ear drum to stretch (possibly rupture)

Question 10

What is Barotrauma

Answer 10

when the ear drum over stretches and ruptures or gets injured due to unequal pressures in the middle ear and outside

Question 11

What happens during a cold/infection

Answer 11

Eustachian tube becomes swollen or blocked, not allowing to release pressure

Question 12

what happens during sinuses

Answer 12

sinuses are airfilled cavities within the skull

if there differential pressure between the outside and the sinuses cavity, you will have headaches, watery eye

Question 13

Solutions?

Answer 13

don’t fly if you have a cold, infection or sinuses because pressures between the middlea ear and the atmosphere is not equalized

swallow or yawn

Valsalva manoevre - pinch your nose and blow hard through it.

Question 14

in what 3 ways can the ear distinguish sound

Answer 14

frequency
timbre
loudness

Question 15

what is the auditory range for an average human

Answer 15

20 Hz to 20,000 Hz

(1Hz is 1 vibration per second)

Question 16

sound is perceived as 3 elements

Answer 16

Frequency: Is the pressure waves per second that sound produces measured in Hz

Loudness: Amplitude/strength of the sound wave measured in Db

Duration : how long the sound lasts

Question 17

what is the scale used to measure loudness

Answer 17

Decible scale - ratio between sound heard and reference level

every 20db is 10x lounder than 0db
40db is 100 x louder
60 db is 1000 x louder…

Question 18

What is the full range of decible scale

Answer 18

0 - 180 dba

Question 19

explain the range of safe to unsafe dba..

Answer 19

below 80 dba = speech
above 80 - 90 dba = chronic exposure that can lead to hearing loss
100 dba= level of physical discomfort
140 - 160 dba=level of paint threshold, ear drum rupture or middle ear ossicles
180 dba=instant hear loss

loud sound can cause fatigue, pain, lack of concentration, inability to communicate over radio

Question 20

What is Noise induced hearing loss

Answer 20

2)Temporary:
hearing might disapper for few hours or days.

**Long terms: **
when you expose yourself to prolonged high intensity sound at 90dba

usually causes damage to the Basilar membrane in inner ear or the hairs inside it

Unable to hear certain sounds clearly/completely or complete loss.

you will gradually 3 to 6 KHZ over in intervals over time

Question 21

Conductive deafness

Answer 21

failure to conduct sounds from outer ear to middle ear due to a defect

caused by:

1) ear drum rupture
2) wax build up in auditory canal
3) Otits Media (ear glue)
4) Osteorclosis - bone build up in the oval window affecting the stapes in the middle ear
5) Barotrauma (air pressure building up) from sinus or infection
6) fluid build up
7) faulty ossicles

Question 22

Presbycusis

Answer 22

age induced hearing loss (usualy higher frequencies are lost)

Question 23

Tinnitus

Answer 23

constant sound being heard, usually high pitched tone.

it can obscure other sounds of similar pitch

can be caused by an infection or injury - where the hairs in the chochiela or the auditory nerve are damaged

Question 24

Vestibular system

Answer 24

In the inner ear

provide info to allow the body to maintain stable posture/balance and stable retina image during movement

Question 25

How does vestibular system help?

Answer 25

• sensing accleration of head movement

-sensing direction of gravitational pull

• controls eye movement

Question 26

if the system is damaged?

Answer 26

not able to balance, dizzy, unsafe vision

Question 27

How does the vestibular system work - linear acceleration

Answer 27

It detects acceleration in linear axis and vertical access (gravity)

1. The (static organ) is connect via a passage from middle ear
2. The organ has 2 chambers- Utricle and Saccule filled with liquid (cupula)
3. There are hairs with crystals called Otolith inside the utricle and saccule

Gravity:
If you tilt your head and there is a 1g gravitational pull, the top heavy hairs will bend in the direction of the gravity, and sends signals to the brain via vestibular nerves.
The brain understand the direction of the tilt with respect to gravity

**In linear accelaration: **
The cupula in the static organ also detects linear accelerations. During a linear acceleration, the body accelerates away from it and the cupula is temporarily ‘left behind’, causing the hairs to bend and send a new signal to the brain. They will return to their normal position once the body is no longer accelerating and is moving at a steady speed (which may be zero).

if your head is tilted back but you are accellerated forward, your braind thinks you are tumbling backwards

Question 28

How does the vestibular system work - angular acceleration

Answer 28

It detects angular acceleration (rotation of the head) in 3 planes

1. There are 3 semi-circular canals integral to the skull positioned at right angles, with fluid inside them (pitch, role, yaw)
2. The semi circular canals end in little bulbs called ampula which have hairs in them

When you rotate your head, the canals move with it.
But since the canals have their own fluid, they have their own inertia - the fluid moves later after the head as moved and in the opposite direction, pushing the hairs into the direction of the head movement (ie head/hair moves opposite of the fluid, during accerlation)

The movement of the fluid in canals cause the hairs in the ampula to bend in the same direction
Each signal from a canal is sensed by the brain as a rotation in each plane

when the angular accelleration is ceased: the fluid moves with the canal in the same direction. Hairs will no longer bend.
Brain will no longer sense any angular accelleration, even if steady angular turn is happening.

Question 29

Spacial Disorientation

Answer 29

Mismatch between the signals recieved by the brain from vestibular system and the visuals seen by your eyes

Such as motion sickness

most reliable sense here is vision to help with this

rely on your instruments

Question 30

symptoms of motion sickness

Answer 30

dizzy, nausea, vomit
hot flushes, clammy hands
headache
fatigue and yawning
salivation
Hyperventilation (fear and anxiety induced)

Question 31

Causes of motion sickness

Answer 31

**vibration of eyeballs **(rapid intake of visual field vs intake from the eye)

simulator sickness: due to the different between simular display and its motion, or its motion vs motion perceived by the pilot

**mismatch accelration:
**when you change acceleration suddenly after being on a constant speed. If you bank after cruising, the change of g force can create a mismatch

Question 32

Solutions to motion sickness

Answer 32

Address the mismatch ideally by

1) fillin in the visual fields with cueues such as focusing on the horizon

2)removing inputs by standing up to gain balance, distracting yourself

3)hydration

4) control breathing and breath more/deeply

5) lay flat/horizontally

Question 33

Vestibular illusions
3 root causes

Answer 33

1. system assumes your body’s linear acceleration is 1 g from head to toe due to gravity.
2. system only detects initial rotational movement

3.system has a threshold under which external stimuli doesn’t trigger any action

Question 34

what is the illusion triggered by linear acceleration

Answer 34

Somatogravic illusion

Question 35

explain this illusion

Answer 35

• Illusion related to linear acceleration
• Usually happens when visual cues are absent
• Example
  
  • If the head is upright and then tilted back, the hairs are deflected back to sense the tilt.
  • But if the head then moves forward but the hairs are still deflected back, the brand doesn’t sense the change
  • Happens with the hair crystals in the Utricle and saccule are deflected and the brain serene the deflection as title even though that head isn’t tilted anymore

Scenario: take off
A large forward acceleration feels like you are pitching up and you end up pushing forward with the controls away

Scenario: landing
A slow forward acceleration feels like you are pitching down

Question 36

what is the illusion affection rotation

Answer 36

**Somotagyral illusion - false perception of rotation
**
Visual queues are not present (ie orbiting at night or in cloud)
The semicircular canals detect an initial angular accerlation.
The natural inertia of the fluid inside the canal causes a pronounced relative movement between the fluid and canal
The hairs of the ampulla are bent

But in a prolonged acceleration, the fluid accelerates at the same speed as the rotation, and hairs stand straight so the body doesn’t sense the angular rotation anymore.

If you stop suddenly, the inertia of the fluid causes the fluid to continue rotation even if the canals stoped. The hair is bent the opposite direction so senses opposite rotation

Question 37

What is LEANS

Answer 37

it’s a type of somotogyral illusion

when you feel that the **aircraft is pitching or rolling **despite the instuments proving otherwise or despite you are at win level - due to the **detection below threshold of the canals (ie movement not detected) **

**Scenario 1
**1)if you make tip to one side quickly that you feel the tilt, and you make and adjustment to wing level slowly/below the detection threshold of the semi circular canals. Your body feels like it’s still tilted to that side and you will lean away from the perceived tilting

Scenario 2
You come to know of a long turn that went un noticed and you make a sudden adjustment to wing level. Your body feels like it’s banking in the opposite direction.

Scenario 3
if let’s say you roll left, you sense this angular accelration
But if you stay in the left turn for 15 sec, the motion is no longer sense and you think you are wing levelled.
you then might roll to the right to try to ‘level’ the wing
the vesitublar system registers you are rolling right from the ‘wing level’,so you are sensing rolling to the right unwantendly

‘graveyeard spiral’

Look at your insturments

Question 38

Coriolis illusion

Answer 38

shifting of the semicircular canals out of their plan of rotaion

Cross coupled stimulation from 2 or more canals

caused by head movement while aircraft is turning - without visual queue

Scenario:
if you look down at your chart while aircraft is turning..and you look up again, Feeling of pitching, rolling or tumbling at the same time

can cause motion sickness and losing control of aircraft

solution: keep head straight relative to the body and avoid extreme head movements while making turns

Question 39

Vertigo

Answer 39

feeling of spinning while stationary / or feeling stationary while you are spinning

brought on by moving the head, heavy accleration

usually a defect in the vestibular system

infection or alchol

sudden pressure change (ie. blowing nose strongly)

flicker vertigo (brought on by flashing light or sunlight reflecting on rotating propellors)

pressure vertigo: flying with block eustachian tube

losing visual reference / horizon reference

going into spins , spiral dives

avoid alchol 3 days prior to flight

Question 40

What is Motion illusion

Answer 40

Inner ear balance mechanism is over stimulated
high g, turbulence
fear and anxity
misbalance from the ear and eye signals (like doing a bank in a simulator visually gives the illusion of a turn, but vestibular signals show straight and not moving)

when your body can’t detect small accelerations making it difficult to sense movement.

Example: train accelerates slowly and vestibular system doesn’t detect this. Without looking out to a fixed reference like the platform, you can’t tell if your train is moving or the other train next to you.

to avoid:
fly aircraft sensibly with control
avoid manoevres that involve unusual gforce
avoid turbelence
ventilate cabin
look out at a distance
recline seat vertically
land if required

Question 41

Habituation

Answer 41

When you have prolonged exposure to stimuli resulting in decreased responses from sensory neurons

Example: If you drive at high speed for a prolonged time and come to exit at low speed, this low speed feels ‘very slow’ because the motion detection apparatus of our visual system has ‘habituated’ to a higher speed

Question 42

what is cocktail party effect

Answer 42

when you can hear a message important to you despite various noises and stimuli

Question 43

how does alchol affect hearing

Answer 43

can induce long/short term hearing.

also drugs/meds

Question 44

How to prevent hearing loss

Answer 44

wear hearing protection like noise canceling headsets, ear plugs and ear muffs

when using radio - lower the volume, and use squelch to control the hash/static

Question 45

can the body sense speed?

Answer 45

no it cannot sense stead speed in a straight line, it can only sense acceleration ( change of speed)

Question 46

what is seat of the pants mean

Answer 46

signals connecting brain to
ear balancing (vestibular) + vision + muscle/tendon and organ propioceptors to sense

these help body react to acceleration, change of speed and direction

Question 47

Types of accerlation: angular and linear

Answer 47

Linear: you go up the elevator and you experience a change in ‘g’ compared to normal

angular: when you spin

Question 48

Vestibullar illusion
of level flight during turning “false up’

Answer 48

Up is always the direction of the g force on your body according to the static organ

if you roll at 60 degrees, you will experience a 2g force on yoru body.

you will feel the anuglar accellartion at tehe beginning when you are in/out of hte turn. However, when the motion stops or stays constant, the fluid goes back to being steady and stops sensing the turn

if your eyes are shut, it will still feel like you are sitting upright but you need your eyes or instruments to confirm that you are not.

Question 49

Orientation - what is it?

Answer 49

ability to determine your position
achieved by:

Vision (strongest sense)
balance (gravity, linear and angular)
seat of the pants( proprioceptive)

Question 50

Vestibullar illusion
of level flight during banking in shallow turn “false up’

Answer 50

pilot might look down at the charts an make a very slow bank and not realize it

its’ because that small rolle was insignificant and the fuid didn’t move in the canals to sense the accleration

Question 51

turns that feel like climb

Answer 51

In a turn, the body experiences a force on the seat-of-the-pants greater than 1g normally exerted on it by the seat in straight-andlevel flight, the same feeling as if the aeroplane was being pulled up from straight-and-level into a climb.

pilot tends to push the control column forward thinking he’ll climb but in fact he’ll descend

Question 52

rolling for lengthy period may feel like a descend

Answer 52

After being in a steady turn for some time, the body gradually gets used to the increased g-forces. Immediately after rolling back to wings-level, and reducing the g-forces to just 1g, the body feels this reduced g-force as less than 1g, the same effect as pushing the nose over into a descent. Use your eyes to check the horizon or the flight instruments to avoid making incorrect inputs on the controls.

Question 53

The Tumbling-Backwards Illusion Caused by Strong Linear Acceleration

Answer 53

In a state of rest or steady velocity (i.e. no acceleration), the body experiences an upward force from the seat. If you now accelerate strongly, there is a further force from the back of the seat accelerating you forwards, and your vestibular apparatus, as well as the seat-of-your-pants, interprets this as a g-force angled forwards.

Since you are used to g-forces always being ‘up’, you interpret the tilted direction of the new g-force as being ‘up’; in other words, you must have tumbled backwards. This is known as the oculogravic illusion or the somatogravic illusion.

a result of this illusion of tumbling backwards during strong accelerations, to want to push the nose of the aeroplane down – a tendency which you can avoid if you use your eyes.

Question 54

The Illusion of Pitching Forwards Caused by Strong Linear Deceleration

**Slowing down may feel like tumbling forwards.
**

Answer 54

The converse happens when you are travelling fast, and then decelerate rapidly. The seat-belt now exerts a force on you, and the resultant g-force from this and the force of gravity is now angled backwards. You sense this direction as ‘up’, so you imagine that you must have pitched forward. The tendency is to pull the control column back, which you can resist if you use your eyes.

Question 55

what happens at the oval window in inner ear?

Answer 55

the vibrating chain of ossicles induces pressure waves in the endolymph

Question 56

inner ear can sense

Answer 56

angular acceleration
linear acceleration
noise

Question 57

human vestibular system performs spatial orientation by

Answer 57

measuring linear and radial acceleration within the inner ear