Year 12 BiologyModule 8 · IQ5⏱ ~45 minPractice bank · 3 Short AnswerLesson 18 of 21
Hearing Loss and Assistive Technologies
Hearing technologies work only when they match the part of the ear that is damaged. Learn the organ structure first, then evaluate hearing aids, cochlear implants and bone-conduction devices.
Today's hook: If a hearing aid makes sound louder but a student still cannot hear speech clearly, which part of the ear might be the problem?
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You’re here
Meet Maya, then set your goals
See where the lesson is heading, meet the newborn whose technology decision you will make, and commit to a first response.
Warm up first
Three quick questions from earlier lessons. Pulling old material back to mind before you learn something new makes the new material stick better, so this is not busywork.
Worksheets
Practise this lesson
Four printable worksheets that build from the foundations up to exam-style questions, start at whatever level suits you.
In 1978 Graeme Clark, at the University of Melbourne, switched on the first multi-channel cochlear implant in Rod Saunders. The device did not make sound louder, it bypassed the exact point where his hearing had failed and fed signals straight to the hearing nerve. That single idea, matching the technology to the damaged structure, is the whole of this lesson.
Learning Intentions
goals
Know
The pathway of sound: outer ear to middle ear to cochlea to auditory nerve to brain
The difference between conductive and sensorineural hearing loss, and what is damaged in each
Three technologies (hearing aid, cochlear implant, BAHA), what each does and who it suits
Understand
Why a cochlear implant produces a different signal to natural hearing, and why that matters
How each technology bypasses or compensates for the specific structure that has failed
Why a BAHA bypasses the outer and middle ear but still needs an intact cochlea
Can Do
Evaluate the benefits, limitations and eligibility of each technology
Recommend and justify a technology for a given patient
Explain why a cochlear implant does not restore normal hearing
Scan these before reading
vocab
CochleaA fluid-filled, coiled inner-ear structure that converts sound vibrations into electrical nerve signals via hair cells.
Hair cellsMechanosensory cells in the organ of Corti whose stereocilia bend as the basilar membrane moves, triggering action potentials.
Tonotopic organisationThe layout of the cochlea in which different frequencies are detected at different positions along the basilar membrane.
Conductive hearing lossLoss caused by a problem in the outer or middle ear (fluid, a perforated eardrum, fused ossicles) that stops sound reaching the cochlea.
Sensorineural hearing lossLoss caused by damage to the cochlear hair cells or auditory nerve; amplification alone cannot correct it.
Cochlear implantA device that bypasses non-functional hair cells and stimulates the auditory nerve directly through electrodes in the cochlea.
Cross-lesson link
L17 looked at genetic disorders and how they are screened for. This lesson turns to a sensory disorder and asks a different syllabus question: how do we assist a person once the disorder is present? Hearing is the clearest case, because the route from outer ear to cortex shows exactly where a technology has to step in.
THINK FIRST · CASE ENTRY
A child born profoundly deaf: what are the options?
Newborn hearing screening finds that a baby girl, Maya, has profound sensorineural hearing loss in both ears. She detects no sound at any frequency, even at maximum amplification with conventional hearing aids. Her parents are told there are technology options that could give her access to sound.
Before reading on, jot down your first thoughts:
Q1 What do you already know about technologies that help people with hearing loss? List anything, hearing aids, cochlear implants, anything else.
Q2 What would you need to know about a technology before recommending it for a newborn? What matters most, for the child and for the family?
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How the ear turns sound into signals
Trace sound from the pinna to the cortex, and find the one structure every hearing technology is built around.
Core Content
Beyond the syllabus. Tonotopic organisation, electrode-channel detail, neural coding and candidacy criteria are extension. For the exam you need the relevant ear structure and function, and how hearing aids, cochlear implants and bone-conduction implants restore hearing.
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Structure and function of the ear
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The auditory pathway: outer ear to auditory cortex
To see why a cochlear implant helps some kinds of deafness but not others, you first need to know how the ear converts a sound wave in the air into an electrical signal the brain can read. Follow the pathway once, and every technology in this lesson becomes a story about which part of it has broken.
Follow the signal from air vibration to perception
Outer ear
The pinna (the visible ear flap) collects sound waves and funnels them down the external auditory canal. The waves make the tympanic membrane (eardrum) vibrate at the same frequency as the incoming sound.
Middle ear
Three tiny bones, the ossicles (malleus, incus and stapes), form a lever system that carries and amplifies the eardrum's vibration to the oval window of the cochlea. This is impedance matching: it converts large, low-pressure vibrations in air into small, high-pressure vibrations in cochlear fluid. The Eustachian tube links the middle ear to the throat and equalises air pressure.
Inner ear (cochlea)
The cochlea is a fluid-filled, snail-shaped tube coiled about 2.75 turns. Movement of the stapes at the oval window sends pressure waves through the cochlear fluid and along the basilar membrane. Different regions of that membrane resonate to different frequencies: high frequencies near the base, low frequencies near the apex. This tonotopic organisation is the basis of pitch discrimination.
Hair Cells to Auditory Cortex
Sitting on the basilar membrane is the organ of Corti, packed with hair cells. Each hair cell carries stereocilia at its tip. When the membrane vibrates, the stereocilia bend, mechanosensitive ion channels open, K⁺ and Ca²⁺ flow in, and the cell depolarises and releases the neurotransmitter glutamate. Glutamate excites the auditory nerve (cranial nerve VIII), firing action potentials that travel to the auditory cortex in the temporal lobe.
Key Point
The cochlea is the transducer, it turns mechanical energy (sound vibration) into electrical energy (action potentials). Every hearing technology in this lesson works by getting a signal to, or past, this point of conversion.
Outer ear (pinna + canal) makes the eardrum vibrate; middle-ear ossicles (malleus, incus, stapes) transmit and amplify to the oval window. In the cochlea the tonotopic basilar membrane (base = high frequency, apex = low frequency) bends hair-cell stereocilia, opening ion channels so the cell depolarises and releases glutamate onto the auditory nerve, sending action potentials to the auditory cortex. The cochlea is the transducer (mechanical to electrical).
Pause, copy the highlighted definition into your book before moving on.
The cochlea acts as the _____, it converts mechanical sound vibration into electrical action potentials.
Interactive · Sound Wave Simulator
Unlock check: Which structure converts sound vibration into electrical signals in the auditory nerve?
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Where hearing breaks down
Conductive or sensorineural: the site of the damage decides which technology can help.
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Two categories of hearing loss
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Different structures, different technologies
We just saw that the cochlea is the transducer. That raises a question: when hearing is lost, where in the pathway is the breakdown, and does that location decide which technology can restore hearing? This card answers it → conductive loss (outer or middle ear, cochlea intact) versus sensorineural loss (hair cells or nerve damaged). Different sites need different technologies.
Conductive hearing loss
Where: outer or middle ear, sound cannot be conducted to the cochlea
Causes: fluid in the middle ear (otitis media), perforated eardrum, earwax blockage, fused or damaged ossicles (otosclerosis)
Cochlea: intact and working, if sound reaches it, transduction is normal
Technologies: hearing aids (amplify past the blockage) or a BAHA (bypass the outer and middle ear via skull vibration)
Prognosis: often treatable, surgery (stapedectomy, tympanoplasty) can fix some causes
Sensorineural hearing loss
Where: inner ear (cochlear hair cells) or the auditory nerve
Technologies: hearing aids for mild-to-moderate loss (boost residual function); cochlear implants for severe-to-profound loss (bypass hair cells, stimulate the nerve)
Prognosis: mammalian hair cells do not regenerate, so the loss is usually permanent
Important distinction
A cochlear implant only helps sensorineural loss when the auditory nerve is intact. If the nerve itself is damaged (rare), an implant has no working fibres to stimulate.
Maya, from Think First, has profound sensorineural loss: her hair cells do not function. A hearing aid only makes sound louder, so with no working hair cells to transduce that louder sound, amplification does nothing for her. She needs a technology that bypasses the hair cells entirely, which points toward a cochlear implant.
Conductive loss: outer or middle ear problem (fluid, perforation, otosclerosis), cochlea intact, so a hearing aid or BAHA suits it. Sensorineural loss: hair cells or auditory nerve damaged, usually permanent (mammalian hair cells do not regenerate), so a hearing aid (mild-to-moderate) or cochlear implant (profound) is used. A cochlear implant needs an intact auditory nerve.
Add the highlighted point to your notes before the check below.
Interactive · Hearing Technology Matcher
Unlock check: In conductive hearing loss, where does the problem lie?
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Three technologies, three routes to the nerve
Hearing aid, cochlear implant and BAHA, how each one works and who it suits.
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Hearing aids
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Amplification for loss where some hair-cell function remains
A hearing aid is an external device that amplifies incoming sound before it reaches the ear. It replaces no biological structure, it simply makes the acoustic signal louder so that surviving cochlear hair cells can respond.
How a hearing aid works
A miniature microphone detects sound waves and converts them to an electrical signal.
An amplifier boosts the signal. Digital aids amplify by frequency, lifting the frequencies where the person has the most loss (for example, high frequencies in presbycusis).
A speaker converts the amplified signal back to louder sound and delivers it into the ear canal.
That louder sound then travels the normal pathway, eardrum, ossicles, cochlea, where residual hair cells transduce it.
Hearing Aid
Evaluation
Benefits Non-invasive, removable, no surgery. Suits mild-to-moderate sensorineural or conductive loss. Digital programming fine-tunes it to the person's audiogram. The Australian Government Hearing Services Program subsidises aids for eligible adults.
Limitations Needs residual hair-cell function, so it is ineffective for profound sensorineural loss (as in Maya's case). Background noise is still hard to manage, batteries need replacing, and it cannot restore hearing to normal.
Eligibility Any patient with measurable residual hearing; most useful for mild-to-moderate loss.
Hearing aid: microphone to amplifier (frequency-specific digital) to speaker, delivering louder sound into the ear canal. The amplified sound still uses the normal pathway, so it needs residual hair-cell function. Best for mild-to-moderate sensorineural or conductive loss; ineffective for profound sensorineural loss. Non-invasive, removable and subsidised for eligible Australians.
Pause, write the highlighted principle into your book.
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Cochlear implants
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Bypassing dead hair cells to stimulate the auditory nerve directly
We just saw that a hearing aid fails when hair cells are gone. That raises a question: if there are no hair cells left to transduce vibration, can we skip them and feed the electrical signal straight to the auditory nerve? This card answers it → a cochlear implant does exactly that, but with only 12 to 22 channels against roughly 3,500 hair-cell positions, so the sound it delivers is different from natural hearing.
Components and how they work
External processor: a microphone picks up sound; a speech processor splits it into frequency bands and codes it as electrical signals.
Transmitter coil: the external coil sends the coded signal across intact skin by radiofrequency induction to the internal receiver, no wire pierces the skin.
Internal receiver-stimulator: implanted under the skin behind the ear, it turns the signal into precisely timed electrical pulses.
Electrode array: a flexible array of 12 to 22 electrodes is threaded into the cochlea. Each electrode sits at a tonotopic frequency position and depolarises the auditory nerve fibres there directly, bypassing the non-functional hair cells.
Auditory nerve to cortex: the resulting action potentials travel via the auditory nerve to the brainstem and on to the auditory cortex, where they are interpreted as sound.
Critical misconception
A cochlear implant does not restore normal hearing. It delivers a different, electrically coded signal the brain has to learn to interpret, with far fewer frequency channels than natural hearing (12 to 22 versus roughly 3,500 hair-cell positions). Music is often poorly appreciated, and recipients describe the sound as robotic at first, needing months of rehabilitation.
Cochlear Implant
Evaluation
Benefits Gives access to sound for people with profound sensorineural loss who gain nothing from hearing aids. Early implantation in children (before roughly age 2 to 3) during the critical period for language dramatically improves speech and language outcomes. Medicare-funded in Australia for eligible patients.
Limitations Irreversible surgery, inserting the array typically destroys any residual hair cells, ruling out future biological treatments. It does not restore natural hearing and needs extensive rehabilitation. There is surgical risk, it fails if the auditory nerve is damaged, and some in the Deaf community regard implanting children too young to consent as controversial.
Eligibility Severe-to-profound sensorineural loss in both ears, inadequate benefit from a hearing-aid trial, a functional auditory nerve, and a commitment to rehabilitation.
Cochlear implant: external processor (mic + speech processor) to RF coil to internal receiver to electrode array (12 to 22) in the cochlea. Electrodes depolarise auditory nerve fibres at tonotopic positions, bypassing dead hair cells. It does not restore normal hearing (12 to 22 channels versus roughly 3,500 hair-cell positions; robotic sound; music is hard). Surgery is irreversible; early childhood implantation gives the best language outcomes; it needs an intact auditory nerve.
Pause, copy the highlighted definition into your book before moving on.
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Bone-anchored hearing aid (BAHA)
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Sending sound through the skull, past the outer and middle ear
We just saw that a cochlear implant bypasses dead hair cells electrically. That raises a question: is there a third route, not through the ear canal and not through electronics inside the cochlea, that still reaches a working cochlea? This card answers it → a BAHA uses bone conduction, sending vibration through the skull straight to a functional cochlea.
The principle of bone conduction
Bone conduction carries sound vibration through the skull bones directly to the cochlea, skipping the air-filled outer and middle ear. You hear your own voice partly this way, which is why a recording of your voice sounds unfamiliar: it captures only the airborne part. Pressing a vibrating tuning fork on the mastoid bone stimulates the cochlea by bone conduction, the basis of the Rinne and Weber tests audiologists use.
How a BAHA works
A titanium screw is anchored into the mastoid bone behind the ear. Over 3 to 6 months the bone grows around it (osseointegration), giving a stable anchor.
An external sound processor clips onto the abutment (or attaches magnetically in newer systems).
The processor turns sound into vibrations and passes them through the titanium into the skull bone.
Those skull vibrations reach the cochlea, move its fluid, and stimulate the hair cells normally, firing the auditory nerve.
Remember!
A BAHA only bypasses the outer and middle ear. It still needs an intact, working cochlea and auditory nerve, so it suits conductive loss and single-sided deafness, not sensorineural loss.
BAHA
Evaluation
Benefits Effective for conductive loss when conventional aids or surgery are unsuitable. Useful for single-sided deafness, routing sound to the working cochlea via bone. Sound is more natural than a cochlear implant because the cochlea still does normal transduction. The external processor is removable and the titanium implant is well tolerated.
Limitations Needs a functional cochlea, so it is not suitable for sensorineural loss. It requires minor surgery, the skin around the abutment can become irritated or infected, and it does not amplify as strongly as a cochlear implant for severe loss. Not suitable for Maya, whose cochlea is non-functional.
Eligibility Conductive or mixed loss where conventional aids do not work, or single-sided deafness. Needs an intact cochlea and auditory nerve (a non-surgical softband is available for young children).
BAHA: a titanium implant osseointegrated in the mastoid bone; the processor turns sound into vibration that passes through the skull to the cochlea, which transduces it normally. It bypasses only the outer and middle ear, so it needs an intact, working cochlea and auditory nerve. Suitable for conductive loss and single-sided deafness, not sensorineural loss. More natural sound than a cochlear implant, but not suitable for Maya.
Add the highlighted point to your notes before the check below.
A conventional hearing aid is effective for profound sensorineural loss where the hair cells are non-functional.
A cochlear implant bypasses damaged hair cells and stimulates the auditory nerve directly with electrical signals.
A BAHA works by amplifying airborne sound waves travelling down the ear canal to the eardrum.
Unlock check: A person has profound sensorineural loss, non-functional hair cells but an intact auditory nerve. Which technology can give them access to sound?
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Evaluate, and decide for Maya
Clear the common traps, make the call for Maya, then apply the whole chain to new patients.
Clear the traps before you evaluate
Common error "A cochlear implant restores normal hearing." +
This is the most penalised error in IQ5 answers. A cochlear implant provides a different signal, electrical stimulation across 12 to 22 channels against roughly 3,500 hair-cell positions, that the brain must learn to read. Music is often badly affected and speech recognition needs months of rehabilitation.
Say it "provides access to sound" or "bypasses hair cells to stimulate the auditory nerve", never "restores hearing".
Common error "A BAHA would suit Maya's profound sensorineural loss." +
A BAHA sends vibration through bone to the cochlea, so it still needs a working cochlea with intact hair cells. Maya's hair cells are non-functional, so a BAHA would deliver vibration a cochlea cannot transduce.
A BAHA is for conductive loss or single-sided deafness, where the cochlea still works.
Common error "A hearing aid works for any type of hearing loss." +
A hearing aid only makes sound louder, so it depends on residual hair-cell function. In profound sensorineural loss there are no working cells to respond, however loud the sound.
Hearing aids help only when enough residual hearing remains.
Which technology is right for Maya?
Maya has profound sensorineural loss in both ears, her hair cells are non-functional. That rules out both hearing aids (need residual hair cells) and a BAHA (needs a working cochlea). Maya is a candidate for bilateral cochlear implantation.
The evidence strongly favours implanting before 12 to 18 months for the best speech and language in profoundly deaf children: the earlier the brain receives auditory input during the critical period, the better it builds auditory processing pathways. By age 3 to 4, cortical reorganisation (the brain reassigning the auditory cortex to other senses) becomes entrenched and later implantation helps less.
There is an ethical dimension too. Maya is too young to consent to an irreversible procedure. Some in the Deaf community argue for delaying until the child can take part in the decision, holding that deafness is a cultural identity with its own language, Auslan, and community, rather than a deficit to correct. This is a genuine debate in Australian healthcare and is examinable in IQ5.
Copy into your book
Auditory pathway
Outer ear: pinna + canal, eardrum vibrates
Middle ear: ossicles (malleus, incus, stapes) amplify and transmit
Inner ear: cochlear hair cells transduce vibration to action potentials
Auditory nerve to brainstem to auditory cortex
Hearing loss types
Conductive: outer or middle ear problem, cochlea intact
Sensorineural: cochlear hair cells or auditory nerve damaged
Cochlear implant: electrodes stimulate the auditory nerve directly, for profound sensorineural loss
BAHA: bone conduction, bypasses outer and middle ear, needs a working cochlea
Critical points
A cochlear implant does not restore normal hearing, different signal, 12 to 22 channels
A BAHA is unsuitable for sensorineural loss
Early cochlear implantation is critical for language in children
The auditory nerve must be intact for a cochlear implant to work
ACTIVITY 1 · SORT + CLASSIFY
Activity 1 · Sort + classify
ApplyBand 4
Matching technology to patient profile
For each patient, choose the most appropriate technology, justify it using the type of loss and the technology's mechanism, and give one limitation for that patient.
James, 72, has age-related sensorineural loss (presbycusis) affecting mainly high frequencies. His audiogram shows moderate loss at 2 to 4 kHz, with measurable residual hearing at all frequencies.
Sophie, 8, was born with bilateral microtia (malformed outer ears) and atresia (no ear canal). Imaging shows her cochleae and auditory nerves are fully intact. She cannot wear a conventional aid because she has no ear canal.
Daniel, 35, lost his cochlear hair cells in both ears to bacterial meningitis at 28 and now has profound bilateral sensorineural loss. His auditory nerves are intact, and he gained no benefit from high-powered hearing aids over a 3-month trial.
ACTIVITY 2 · ANALYSE + CONNECT
Activity 2 · Analyse + connect
AnalyseBand 5
Evaluating cochlear implant technology
Apply the cochlear implant mechanism to these analysis questions.
A cochlear implant array has 22 electrodes; the cochlea normally has roughly 3,500 inner hair cells, each tuned to a slightly different frequency. Explain why this difference in channel number matters for sound quality, and why recipients often find music harder than speech.
The Australian Cochlear Implant Program recommends implanting profoundly deaf children as early as possible, ideally before 12 months. Using neural development and auditory processing, explain the biological basis for this, and describe evidence that would support or challenge it.
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Independent practice
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Multiple Choice
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A fresh set drawn from this lesson's question bank, feedback shown immediately. +5 XP per correct · +25 XP all correct
Pick your answer, then rate your confidence, that tells the system what to drill next.
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Short Answer, 14 marks
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ApplyBand 3–4(3 marks) 1. Distinguish between conductive hearing loss and sensorineural hearing loss in terms of: (a) the anatomical site of the problem, (b) the integrity of the cochlear hair cells, and (c) the hearing technology most appropriate for each.
AnalyseBand 4–5(5 marks) 2. Describe the mechanism by which a cochlear implant provides hearing to a person with profound sensorineural hearing loss. Identify what structure is bypassed, how the electrical signal is delivered to the auditory nerve, and explain why the sound perceived is different from normal hearing.
EvaluateBand 5–6(6 marks) 3. Evaluate the use of cochlear implantation as a technology to assist people with profound sensorineural hearing loss. Describe how the technology works, discuss the benefits (including evidence for early implantation in children), identify the limitations, and consider one social or ethical dimension.
Show all answers
Multiple choice
MC answers and full explanations are shown inline as you complete each question. Use the retry button to attempt a fresh set from the lesson bank.
Short Answer Model Answers
SA1 (3 marks): (a) Conductive loss is in the outer ear (pinna, canal, eardrum) or middle ear (ossicles, Eustachian tube); sensorineural loss is in the inner ear (cochlear hair cells) or auditory nerve [1]. (b) In conductive loss the cochlear hair cells are intact and functional, if sound reaches the cochlea, transduction is normal; in sensorineural loss the hair cells are damaged/absent and cannot transduce vibration regardless of how much sound reaches them [1]. (c) Conductive → hearing aid (amplifies sound to overcome the barrier) or BAHA (bypasses outer/middle ear via bone vibration to the intact cochlea); sensorineural → hearing aid for mild-moderate loss with residual function, cochlear implant for severe-profound loss (electrode array directly stimulates the intact auditory nerve, bypassing dead hair cells) [1].
SA2 (5 marks): Structure bypassed: cochlear hair cells (organ of Corti), non-functional in profound SNHL [1]. Mechanism: an external behind-the-ear processor's microphone captures sound; a speech processor divides it into frequency bands and generates coded electrical signals; these are transmitted by radiofrequency induction across intact skin to an internal receiver-stimulator; the receiver delivers precisely timed pulses to a 12–22-electrode array threaded into the cochlea; each electrode sits at a tonotopic frequency position and directly depolarises the auditory nerve fibres there; action potentials travel via the auditory nerve to the cochlear nucleus, brainstem and auditory cortex [2.5]. Why it sounds different: the normal cochlea provides ~3,500 frequency-tuned hair cell positions (fine pitch resolution); a CI provides only 12–22 broad channels, so pitch discrimination is reduced, harmonic overtones/timbre (especially music) are poorly encoded, and the brain must learn to interpret an unfamiliar simplified signal, often described as "robotic", requiring months of rehabilitation [1.5].
SA3 (6 marks): How it works: an external sound processor analyses sound and transmits coded signals via electromagnetic induction to an internal receiver, which delivers electrical pulses through a 12–22-electrode array in the cochlea; each electrode stimulates auditory nerve fibres at a tonotopic position, bypassing non-functional hair cells [1]. Benefits: provides access to sound for those with profound SNHL who gain no benefit from hearing aids; the strongest evidence is in children, early implantation (before 12–18 months) during the critical period of auditory cortex development enables speech and language approaching hearing peers, whereas delayed implantation allows cortical reorganisation that narrows the window; in adults, CI restores meaningful communication; Medicare-funded in Australia [2]. Limitations: irreversible (destroys residual hair cells, precluding future biological therapies); does not restore natural hearing (12–22 channels vs ~3,500 hair cells → poor pitch resolution, impaired music); requires general-anaesthetic surgery and extensive rehabilitation; ineffective if the auditory nerve is damaged; outcomes vary [2]. Social/ethical dimension: implanting young children is ethically complex because the child cannot consent to an irreversible procedure; some in the Deaf community view deafness as a cultural identity (with its own language, Auslan, and community) rather than a deficit to be corrected, and argue implantation without consent denies the child a Deaf identity, a genuine tension between the medical and social models of disability [1].
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Retrieve and reflect
Check what actually stuck
Take the full module quiz
quiz
A full module quiz covering every lesson in this module, not just this one. Set aside a decent block of time and treat it like a real assessment.
Defend your ship by blasting the correct answers for Hearing Loss, Cochlear Implants and Bone Conduction. Scores count toward the Asteroid Blaster leaderboard.
Answer questions on the ear, hearing loss types, and the three hearing technologies. Pool: lessons 1–18.
Which technology is right for Maya?
Return to your Think First responses about Maya and connect them to the WHO World Hearing Report 2021 and Graeme Clark's 1978 innovation. Clark's cochlear implant at the University of Melbourne was designed specifically for profound sensorineural hearing loss, where hair cells are non-functional, by directly stimulating the auditory nerve via an electrode array. The WHO projects that by 2050, 2.5 billion people (25%) will have some degree of hearing loss; 700,000+ already use Clark's device globally, making it the most successful neural prosthetic in history.
Q1, Technologies and the 1978 Clark innovation: Can you describe all three? Hearing aid (amplification, needs residual hair-cell function), cochlear implant (Clark 1978: electrode array directly stimulates auditory nerve, bypasses non-functional hair cells, for profound SNHL), BAHA (bone conduction, bypasses outer/middle ear, needs intact cochlea). Which is appropriate for Maya (profound sensorineural hearing loss) and why?
Q2, Factors for recommendation: Type of hearing loss (profound sensorineural), auditory nerve status (must be intact for CI, Clark's device depends on this), age at implantation (critical period, before 12–18 months for best outcomes), irreversibility, rehabilitation commitment, and the ethical dimension of infant consent.
Write the recommended technology for Maya, the biological reason (referencing Clark's 1978 mechanism, electrode array → auditory nerve → bypasses hair cells), the key benefit (WHO: 700,000+ functional users), and one limitation (22 channels vs 3,500).