Hearing/Balance And Spatial Awareness Flashcards
Describe the basic anatomy of the ear.
- Outer ear = external ear (pinna) and eardrum
- Middle ear = ossicles (malleus, incus, stapes) and Eustachian tube
- Inner ear = the semi-circular canals and cochlea
What are the two functions of the ear?
- Hearing
- Balance and acceleration
Sound waves travel through the ear canal and vibrate the ear drum - this vibration transfers to the ossicles which in turn vibrates the cochlea. This causes fluid inside the cochlea to move which produce electrical signals that are transmitted to the brain.
These signals are processed and perceived as sound.
Explain the effect of prolonged noise exposure on hearing.
- Short-term exposure to a loud sound can be as bad as a long term exposure to a less intense sound.
This is linked with cardiovascular disease - high blood pressure.
Also common: cholesterol issues, gastric ulcers, sleep disturbances and mental stress.
Explain the two types of hearing loss.
Conductive = Sound waves are blocked from reaching the inner ear. Most common with children who have recurring ear infections, or put things in their ears.
Sensorineural = Inner ear, hair within the cochlea becomes damaged. Receives signals but can’t process. Most common with age.
What are some methods of hearing protection?
- Earplugs
- Earmuffs
- Comms headset
- Earmuff/Helmet Combinations
State the various levels of noise in decibels at which various grades of hearing protection are required.
85 and below = no protection needed
86 to 91 = Grade 1 earmuffs or plugs
92 to 97 = Grade 2 earmuffs muffs
98 to 103 = Grade 3 earmuffs or plugs
104 to 109 = Grade 4 earmuffs or plugs
110 to 115 = Grade 5 earmuffs or plugs
What are the noise levels at which hearing damage may occur?
- Temporary hearing impairment = steady noise over 90dB over a short time (possibly several hrs)
- Permanent hearing damage = noise over 85dB for 8hrs or more per day for several years
- Immediate hearing loss = a sudden noise of 140dB to 150dB
What is the action threshold for hearing protection?
The level of noise exposure above which active steps should be taken in order to avoid the harmful effects of the noise on hearing.
What are the effects of age induced hearing loss (presbycusis)?
- The loss of hearing that occurs as people get older generally occurs slowly over time.
Symptoms:
- difficulty hearing people
- frequently asking people to repeat themselves
- frustration at not being able to hear
- certain sounds seem overly loud
- problems hearing in noisy areas
- problems telling apart sounds such as “s” or “th”
- more difficulty understanding people with higher pitched voices
- ringing in the ears
Explain the effects of pressure changes on the middle ear and Eustachian tubes.
- It is normally closed but opens occasionally when we: yawn, swallow or chew.
This allows air to flow into the middle ear and any mucus to flow out.
Air pressure is kept equal either side of the eardrum and allows it to work and vibrate properly.
If it is blocked when on descent - air pressure pushes against the eardrum causing it to become tense and leads to severe pain.
What the are effects of cold, hay fever and/or allergies on the sinuses and Eustachian tubes?
- Mucus that develops may block Eustachian tube = unequal pressure
If Valsalva doesn’t work - don’t fly
What is spatial orientation?
The ability to correctly interpret the aircraft attitude, altitude or airspeed in relation to the Earth or point of reference.
What is disorientation?
- Where time, direction and recognition of people and places become difficult to distinguish.
6% to 32% of major accidents, 15% to 69% of fatal accidents
- Happens anytime, anywhere
Describe the physiology of the motion, orientations and gravitational sensory organs - semi-circular canals:
- Made of three: Posterior, superior and horizontal
All linked at right angles with each other - Filled with liquid which shifts in response with rotation acceleration of the body
- Angular acceleration in any plane will stimulate at least two of the canals
Describe the physiology of the motion, orientations and gravitational sensory organs - vestibular sac/tubes:
- Two otolith organs in each inner ear (utricle and saccule)
Within each organ there is a gelatinous substance surrounding hair like cells which sense linear acceleration from the movement of the substance.
- Sense both head/body and longitudinal acceleration
Explain the interconnection between visual and kinaesthetic senses in maintaining accurate spatial orientation.
The thousands of nerve endings in joints, muscles and especially that neck generate information on movement and position = proprioceptors
Explain the body’ limitations in maintaining spatial orientation when vision is adversely affected:
In the absence of normal visual inputs, incorrect information from the vestibular system can lead to pilot disorientation or motion sickness or both.
What are the effects of the leans and sub-threshold stimulation?
- Leans = strong sensation felt by pilots as being one attitude when all aircraft instruments are indicating something else
- Sub-threshold stimulation = caused by slow rolling of the aircraft that isn’t picked up by the semi-circular canals. If the pilot notices and corrects it from the instruments, can lead to the leans
What are the effects of somatogravic illusion?
Otolith cannot distinguish between a rapid longitudinal acceleration and body/head tilt backwards, a powerful but erroneous sensation of a steep climb can occur in the even of a rapid takeoff or missed approach/go around.
Leads to pilot induced descent and crash by flying into the ground.
What are the effects of somatogyral illusion?
- When the pilot has the leans but it not aware of it - aircraft has entered a spiral dive.
As the speed build, the pilot believes the aircraft is in a wings level dive and tries to pull of the dive - the aircraft has considerable bank and therefore increases the intensity of the spiral dive.
AKA ‘graveyard spiral’.
What are the effects of cross coupled turning (Coriolis effect)?
- Nausea and disorientation produced by head movement during turning manoeuvres in aircraft
What are the effects of pressure vertigo?
- Can be triggered by a collapse of eardrums due to blocked Eustachian tubes - flying with blocked sinuses
Leads to a perforation of the eardrum resulting in nausea and vertigo.
What are the factors which affect an individual’s susceptibility to disorientation?
- Flying with a cold or illness
- Flying after alcohol use
- Lack of instrument or night proficiency
How can disorientation be prevented?
- No ‘seat of the pants’ flying.
- When in reduced visibility or night - use instruments, transition to them early
- Maintain instrument and night proficiency
TRUST YOUR INSTRUMENTS!
