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Military hearing loss glossary

Plain-English definitions of the medical, military and legal terms in military hearing-loss claims, from audiogram and rM-NIHL to Crown immunity and AFCS.

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15 May 1987

Also called: 1987 cut-off · Crown Proceedings (Armed Forces) Act 1987

The date the Crown Proceedings (Armed Forces) Act 1987 removed the old section 10 Crown immunity prospectively. The Act preserves that immunity for anything suffered in consequence of an act or omission committed before 15 May 1987. In service spanning the date, post-1987 exposure may still be relevant. It is a legal boundary, not a medical or compensation-scheme boundary.

See also: Crown immunity, 6 April 2005, Combat immunity

Sourced from: Statute and civil procedure governing military personal-injury claims

6 April 2005

Also called: 2005 boundary · AFCS start date

The broad dividing date between the two statutory service-compensation schemes. AFCS covers injury or illness caused by service on or after 6 April 2005; WPS covers disablement caused or made worse by service before that date. Service spanning the boundary can require closer analysis. It has nothing to do with Crown immunity or ordinary civil limitation.

See also: AFCS (Armed Forces Compensation Scheme), WPS (War Pension Scheme), 15 May 1987

Sourced from: Armed Forces Compensation Scheme — current rules and guidance; War Pension Scheme — current rules and guidance

A

Acoustic trauma

Also called: acute acoustic trauma · blast injury to the ear

Sudden hearing damage from a single very loud sound — an explosion, a weapon fired close by, a blast in a confined space. It differs from ordinary noise-induced hearing loss, which builds over years. Symptoms often start immediately and can include pain, muffled hearing, ringing or a perforated eardrum.

Sudden hearing loss is a medical emergency. Anyone who loses hearing suddenly should seek urgent care the same day rather than waiting to see whether it settles.

See also: NIHL (noise-induced hearing loss), Tinnitus, Temporary threshold shift

Sourced from: NHS and NICE clinical guidance on hearing and tinnitus; MOD noise-at-work policy and hearing surveillance (JSP 375)

AFCS (Armed Forces Compensation Scheme)

Also called: AFCS compensation · Armed Forces Compensation Scheme

The MOD-run no-fault scheme covering injury and illness caused by service on or after 6 April 2005. You do not have to prove anyone was negligent, but there is normally a seven-year window to claim. It is separate from a civil claim and from the older War Pension Scheme.

See also: WPS (War Pension Scheme), 6 April 2005, Quinquennial review, IMEG (Independent Medical Expert Group)

Sourced from: Armed Forces Compensation Scheme — current rules and guidance

Air conduction

Testing hearing the normal way — sound travels through headphones or earphones, down the ear canal, through the middle ear and into the cochlea. It measures the whole hearing pathway. Comparing it with bone conduction is how an audiologist works out where in the ear the problem lies.

See also: Bone conduction, Audiogram, Sensorineural hearing loss, Mixed hearing loss

Sourced from: NHS and NICE clinical guidance on hearing and tinnitus

Audiogram

Also called: hearing test · pure-tone audiogram · PTA · pure-tone audiometry

The standard chart of your hearing. You signal when you can just hear tones at different pitches, and the quietest level you detect at each is plotted. Pitch runs left to right, and quieter hearing is plotted further down the chart — so a line that drops to the right means worse hearing at high frequencies.

See also: dB HL (decibels hearing level), Notch, Masking, Air conduction, Bone conduction

Sourced from: NHS and NICE clinical guidance on hearing and tinnitus

B

Bone conduction

Testing hearing with a small vibrator placed on the bone behind the ear, sending sound to the cochleae while largely bypassing the outer and middle ear. Comparing bone- and air-conduction thresholds helps identify a conductive component. Where the ears differ enough, masking may be needed so the non-test ear does not produce a falsely good result.

See also: Air conduction, Audiogram, Sensorineural hearing loss, Mixed hearing loss

Sourced from: NHS and NICE clinical guidance on hearing and tinnitus

C

Causation

The link between the exposure complained of and the injury suffered. In a hearing claim it is not enough to show that service was noisy and that you now have hearing loss. The evidence has to support the conclusion that the noise caused this loss, rather than age, illness or civilian noise.

See also: NIHL (noise-induced hearing loss), Presbycusis, rM-NIHL, Notch

Sourced from: Statute and civil procedure governing military personal-injury claims; Abbott and others v Ministry of Defence [2026] EWHC 941 (KB)

Cochlea

The spiral, fluid-filled part of the inner ear that turns sound into nerve signals. It is lined with hair cells, each tuned to a different pitch. Loud noise damages these hair cells, and in humans they do not grow back — which is why noise-induced hearing loss is permanent.

See also: NIHL (noise-induced hearing loss), Sensorineural hearing loss, Hair cells

Sourced from: NHS and NICE clinical guidance on hearing and tinnitus

Combat immunity

A common-law doctrine that can limit negligence liability for acts or decisions closely connected with actual or imminent armed conflict. It is distinct from the historic statutory Crown immunity removed prospectively in 1987. Routine training, ranges and ordinary military workplace activity do not become combat merely because weapons or military equipment are involved.

See also: Crown immunity, 15 May 1987

Sourced from: Statute and civil procedure governing military personal-injury claims

Crown immunity

The historic protection in section 10 of the Crown Proceedings Act 1947 that restricted tort claims by service personnel. The Crown Proceedings (Armed Forces) Act 1987 removed it prospectively from 15 May 1987, while preserving it for injury suffered in consequence of pre-Act acts or omissions. Service spanning that date therefore needs the exposure timeline examined.

The statute turns on the timing of the relevant act or omission and what was suffered in consequence of it, not simply the enlistment, discharge or diagnosis date.

See also: 15 May 1987, Combat immunity, WPS (War Pension Scheme)

Sourced from: Statute and civil procedure governing military personal-injury claims

D

Date of knowledge

The point at which you first knew, or could reasonably have been expected to know, that you had a significant injury and that it might be attributable to something the MOD did or failed to do. Limitation for a personal-injury claim usually runs from this date rather than from the noise exposure itself.

See also: Limitation period, Section 33 discretion

Sourced from: Statute and civil procedure governing military personal-injury claims

dB HL (decibels hearing level)

Also called: decibel hearing level · hearing threshold level

The scale used on an audiogram. Zero is roughly the quietest sound a healthy young adult can hear at that pitch, so it is a comparison against normal hearing rather than an absolute measure. Higher numbers mean sound must be louder before you hear it — that is, worse hearing.

See also: Audiogram, LAeq / daily personal noise exposure

Sourced from: NHS and NICE clinical guidance on hearing and tinnitus

Disease and Illness Protocol

Also called: Pre-Action Protocol for Disease and Illness Claims

The pre-action rules governing how a disease claim — including hearing loss — is notified and investigated before proceedings are issued. It sets out what a letter of claim should contain and how long a defendant has to respond. Its fixed-cost annex for noise-induced hearing loss expressly excludes military claims.

See also: Limitation period, Witness statement

Sourced from: Statute and civil procedure governing military personal-injury claims

G

General damages

Compensation for the injury itself and its effect on your life — the hearing loss, the tinnitus, the difficulty following conversation. It is assessed by reference to published judicial guidelines and reported cases, not by a fixed tariff, and it is separate from money for financial losses.

See also: Special damages, Quantum, Smith v Manchester award

Sourced from: Statute and civil procedure governing military personal-injury claims; Abbott and others v Ministry of Defence [2026] EWHC 941 (KB)

Group litigation

Also called: GLO · group litigation order

A way of managing many claims that raise common issues. A formal Group Litigation Order is a specific procedure under the Civil Procedure Rules. Abbott expressly says the Military Deafness Litigation was not conducted under a formal GLO, although it used similar features including common case management, a Group Register, generic issues, common costs and lead cases.

See also: Matrix (MOD Matrix Agreement), Causation

Sourced from: Abbott and others v Ministry of Defence [2026] EWHC 941 (KB)

H

Hair cells

The sensory cells inside the cochlea that convert vibration into nerve signals. Each responds to a particular pitch. Loud noise can damage or destroy them, and once lost they are not replaced — the reason noise damage accumulates over a career and does not recover.

See also: Cochlea, NIHL (noise-induced hearing loss), Permanent threshold shift

Sourced from: NHS and NICE clinical guidance on hearing and tinnitus

Hearing aid

A device that amplifies sound to compensate for hearing loss. It does not restore normal hearing or repair the ear; it makes better use of the hearing you have. NHS hearing aids are digital, individually programmed to your audiogram, and provided with batteries and servicing at no cost.

See also: Audiogram, Speech-in-noise difficulty

Sourced from: NHS and NICE clinical guidance on hearing and tinnitus

Hearing protection

Also called: PPE · ear defenders · earplugs

Earplugs, earmuffs and electronic defenders issued to reduce noise reaching the ear. Under MOD policy it is a control of last resort: noise is supposed to be reduced at source first, and protection has to be suitable, correctly fitted and actually worn to achieve the reduction it claims.

See also: Noise exposure action values, LAeq / daily personal noise exposure

Sourced from: MOD noise-at-work policy and hearing surveillance (JSP 375)

Hearing surveillance

Also called: audiometric surveillance · health surveillance

A programme of periodic hearing assessment for personnel who are likely to be regularly exposed above the upper noise action values, or are otherwise at risk. Current JSP 375 requires a personal health-surveillance record using MOD Form 5051. That occupational-health record is distinct from confidential medical information, which is kept in the medical record.

See also: Recruitment audiogram, Noise exposure action values, Audiogram

Sourced from: MOD noise-at-work policy and hearing surveillance (JSP 375)

Hyperacusis

Reduced tolerance of ordinary sound, where everyday noise — cutlery, traffic, a hand dryer — feels uncomfortably or painfully loud. It is not the same as hearing loss and can occur alongside normal hearing. It often accompanies tinnitus and is assessed and managed by audiology.

See also: Tinnitus, Acoustic trauma

Sourced from: NHS and NICE clinical guidance on hearing and tinnitus

I

IMEG (Independent Medical Expert Group)

An independent MOD-sponsored expert body that advises the Minister on medical and scientific aspects of AFCS and related matters. Its membership includes senior medical consultants as well as ex-service and ex officio members. IMEG reviews published evidence and makes recommendations, but it does not decide individual claims or itself make AFCS policy.

See also: AFCS (Armed Forces Compensation Scheme), Quinquennial review

Sourced from: Armed Forces Compensation Scheme — current rules and guidance

Interim payment

A payment made on account before the final value of a claim is resolved. Under CPR Part 25, the court can order one in specified circumstances, including where liability is admitted, judgment has been obtained, or the court is satisfied the claimant would recover a substantial sum at trial. It is deducted from the final award, not added to it.

See also: Quantum, General damages

Sourced from: Statute and civil procedure governing military personal-injury claims

L

LAeq / daily personal noise exposure

Also called: LEP,d · A-weighted equivalent level

A way of expressing noise as a single figure averaged over time, weighted for how the ear responds. It lets a short burst of very loud noise and a long spell of moderate noise be compared. Daily personal noise exposure applies this over a nominal eight-hour working day.

See also: Noise exposure action values, dB HL (decibels hearing level), Hearing protection

Sourced from: MOD noise-at-work policy and hearing surveillance (JSP 375)

Limitation period

The time limit for starting a civil claim. For personal injury the ordinary period is generally three years from accrual or the claimant’s later date of knowledge. Section 33 can sometimes allow a late claim to proceed, but that discretion is not automatic and special statutory rules, including the overseas-operations longstop in qualifying cases, can restrict it.

See also: Date of knowledge, Section 33 discretion, Overseas Operations Act longstop

Sourced from: Statute and civil procedure governing military personal-injury claims

M

Masking

A technique used during audiometry in which noise is presented to the non-test ear when needed to prevent it from detecting the test signal. Masking helps establish the true threshold of the ear being tested and distinguish conductive from sensorineural components. It is not required for every test point, and its presence alone does not prove the whole audiogram was performed correctly.

See also: Audiogram, Air conduction, Bone conduction

Sourced from: NHS and NICE clinical guidance on hearing and tinnitus

Matrix (MOD Matrix Agreement)

Also called: Matrix Agreement · the Matrix

An agreement used within the Military Deafness Litigation to dispose of recurring issues including Crown immunity, combat immunity, breach, contributory negligence, apportionment, Noise Immission Level and limitation. It leaves individual causation and quantum to be determined, in return for a structured discount on damages. Current RBL guidance gives 23:59 on 31 January 2027 as the Matrix deadline.

The agreement recorded in Abbott was reached with a particular claimant cohort. Do not assume it is available on identical terms through any firm.

See also: Group litigation, AFCS (Armed Forces Compensation Scheme), WPS (War Pension Scheme), Quantum

Sourced from: The MOD Matrix Agreement — current registration position; Abbott and others v Ministry of Defence [2026] EWHC 941 (KB)

Mixed hearing loss

Hearing loss where a sensorineural component and a conductive component occur in the same ear. Bone-conduction thresholds show the underlying inner-ear hearing loss while poorer air-conduction thresholds show an additional outer- or middle-ear component. The two components may have different causes and may need different treatment.

See also: Sensorineural hearing loss, Air conduction, Bone conduction, Audiogram

Sourced from: NHS and NICE clinical guidance on hearing and tinnitus

N

NIHL (noise-induced hearing loss)

Also called: military deafness · noise-induced hearing loss · industrial deafness

Permanent sensorineural hearing loss caused by excessive noise exposure. It commonly affects higher frequencies and is often bilateral, but military firearm exposure can produce meaningful asymmetry between the ears. Diagnosis depends on the exposure history, audiometric pattern and clinical context, including alternative causes such as age or disease. A noisy military job does not establish NIHL by itself.

See also: Cochlea, Notch, Presbycusis, rM-NIHL, Causation

Sourced from: NHS and NICE clinical guidance on hearing and tinnitus

Noise exposure action values

Also called: lower exposure action value · upper exposure action value

Noise levels at which specific duties are triggered — assessing exposure, providing information and hearing protection, marking hearing-protection zones and offering hearing checks. There is also an exposure limit value that must not be exceeded once the protection actually worn is taken into account.

See also: LAeq / daily personal noise exposure, Hearing protection, Hearing surveillance

Sourced from: MOD noise-at-work policy and hearing surveillance (JSP 375)

Notch

Also called: audiometric notch · noise notch

A dip in the audiogram around 3, 4 or 6 kHz with better hearing on either side, classically associated with noise damage. It is a pointer, not a diagnosis: notches can be absent in genuine noise damage and present for other reasons, and age-related loss can fill one in over time.

See also: Audiogram, NIHL (noise-induced hearing loss), rM-NIHL, Presbycusis

Sourced from: NHS and NICE clinical guidance on hearing and tinnitus; Abbott and others v Ministry of Defence [2026] EWHC 941 (KB)

O

Overseas Operations Act longstop

Also called: Overseas Operations (Service Personnel and Veterans) Act 2021

A special six-year limitation longstop for certain civil claims connected with qualifying overseas operations. Broadly, it prevents a claim being brought more than six years after the incident or more than six years after the claimant’s date of knowledge, whichever is later. It does not apply simply because somebody served abroad, and its statutory conditions must be satisfied.

See also: Limitation period, Section 33 discretion, Date of knowledge

Sourced from: Statute and civil procedure governing military personal-injury claims

P

Permanent threshold shift

A deterioration in hearing threshold after noise exposure that does not return to the pre-exposure level after the recovery period. Permanent threshold shift reflects lasting auditory injury, which can involve cochlear hair cells, synapses and neural structures. It should not be reduced to a simple “fatigued cells versus destroyed cells” distinction because the underlying mechanisms are more complex.

See also: Temporary threshold shift, Hair cells, NIHL (noise-induced hearing loss)

Sourced from: NHS and NICE clinical guidance on hearing and tinnitus

Presbycusis

Also called: age-related hearing loss

Hearing loss that comes with age, affecting high frequencies first and gradually. Because it looks similar to noise damage on an audiogram, separating the two is central to any hearing claim — and it is why expert evidence usually tries to estimate how much loss age alone would explain.

See also: NIHL (noise-induced hearing loss), Causation, Notch, rM-NIHL

Sourced from: NHS and NICE clinical guidance on hearing and tinnitus

PULHHEEMS

Also called: H grade · H1 · H2 · H3 · H4 · medical employment standard

The UK Armed Forces profile used to standardise medical functional assessment. Its letters cover Physical Capacity, Upper Limbs, Locomotion, Hearing Acuity in each ear, Visual Acuity in each eye, Mental Capacity and Stability. PULHHEEMS helps inform military employability; its hearing grades describe hearing acuity, not diagnosis, causation or compensation percentages.

See also: Audiogram, Hearing surveillance, NIHL (noise-induced hearing loss)

Sourced from: Armed Forces Compensation Scheme — current rules and guidance

Q

Quantum

The value of a claim, as opposed to whether it succeeds at all. Liability asks whether the defendant is responsible; quantum asks what that is worth. A claim can succeed on liability and still be worth very little, and the two are often argued and decided separately.

See also: General damages, Special damages, Matrix (MOD Matrix Agreement), Smith v Manchester award

Sourced from: Statute and civil procedure governing military personal-injury claims; Abbott and others v Ministry of Defence [2026] EWHC 941 (KB)

Quinquennial review

The periodic review of the Armed Forces Compensation Scheme, held roughly every five years, which examines whether the scheme rules and tariff remain appropriate and takes evidence from veterans and expert bodies. Its progress updates are published by the MOD.

See also: AFCS (Armed Forces Compensation Scheme), IMEG (Independent Medical Expert Group)

Sourced from: Armed Forces Compensation Scheme — current rules and guidance

R

Recruitment audiogram

Also called: entry audiogram · baseline hearing test

A hearing test performed at or around entry to service that can provide an important baseline before later military noise exposure. Comparing it with subsequent audiograms may help show when thresholds changed and by how much. Its absence can make reconstruction harder, but no single recruitment audiogram by itself determines whether current hearing loss was caused by service.

See also: Hearing surveillance, Audiogram, Causation

Sourced from: MOD noise-at-work policy and hearing surveillance (JSP 375); Abbott and others v Ministry of Defence [2026] EWHC 941 (KB)

rM-NIHL

Also called: revised M-NIHL · revised military NIHL method

A revised military-NIHL diagnostic method developed by Moore and colleagues, using quantitative age-corrected high-frequency audiometric criteria including Mag(Notch) and Mag(ExcessHF). Abbott preferred rM-NIHL to the older CLB approach for the military cases before the Court. It is a diagnostic aid, not a legal test, and the final diagnosis still requires the full medical and noise-exposure history.

See also: Notch, NIHL (noise-induced hearing loss), Presbycusis, Causation

Sourced from: NHS and NICE clinical guidance on hearing and tinnitus; Abbott and others v Ministry of Defence [2026] EWHC 941 (KB)

S

Section 33 discretion

The discretionary power under section 33 of the Limitation Act 1980 to let an otherwise late personal-injury claim proceed where it is equitable to do so. The court considers all the circumstances, including the length and reasons for delay and the effect on the evidence. It is never a right, and separate statutory longstops can restrict whether the discretion remains available.

See also: Limitation period, Date of knowledge, Overseas Operations Act longstop

Sourced from: Statute and civil procedure governing military personal-injury claims

Sensorineural hearing loss

Hearing loss caused by damage to the inner ear or the hearing nerve, rather than a blockage or problem in the outer or middle ear. Noise damage, age-related loss and many congenital losses are sensorineural. It is generally permanent and is managed with hearing aids rather than cured.

See also: Cochlea, NIHL (noise-induced hearing loss), Air conduction, Bone conduction, Mixed hearing loss

Sourced from: NHS and NICE clinical guidance on hearing and tinnitus

Smith v Manchester award

Also called: handicap on the labour market

Compensation for being at a disadvantage in the job market because of an injury — the risk that if you lost your job you would find it harder to get another. It is awarded where that disadvantage is real rather than speculative, and it is separate from lost earnings already incurred.

See also: Special damages, General damages, Quantum

Sourced from: Statute and civil procedure governing military personal-injury claims

Special damages

Compensation for financial losses you can actually count — lost earnings, travel to appointments, the cost of equipment or treatment. Unlike general damages they are proved with documents rather than assessed by comparison with other cases, so records and receipts matter.

See also: General damages, Quantum, Smith v Manchester award

Sourced from: Statute and civil procedure governing military personal-injury claims

Speech-in-noise difficulty

Also called: difficulty in background noise · cocktail party problem

Difficulty understanding speech when other sound is present, such as in restaurants, vehicles or group conversations. Pure-tone audiometry does not reproduce those real-world listening conditions, so some people report greater speech-in-noise difficulty than their audiogram alone would suggest. It is a functional hearing problem that may require separate assessment rather than being read directly from pure-tone thresholds.

See also: NIHL (noise-induced hearing loss), Hearing aid, Audiogram

Sourced from: NHS and NICE clinical guidance on hearing and tinnitus

T

Temporary threshold shift

Also called: TTS · muffled hearing after noise

A temporary worsening of hearing thresholds after noise exposure that later returns to the pre-exposure level. Recovery can take minutes, hours, days or longer depending on the exposure and the individual. A recovered audiogram does not prove the exposure was harmless: research shows temporary threshold shifts can involve cochlear changes, and repeated harmful exposures can contribute to permanent injury.

See also: Permanent threshold shift, Acoustic trauma, NIHL (noise-induced hearing loss)

Sourced from: NHS and NICE clinical guidance on hearing and tinnitus

Tinnitus

Also called: ear ringing · ringing in the ears

Hearing sound that has no external source — ringing, buzzing, hissing or humming. It is a symptom rather than a disease, and it commonly accompanies noise damage. It can occur with normal hearing, and its severity is not measured by an audiogram but by its effect on sleep, concentration and mood.

See also: Hyperacusis, NIHL (noise-induced hearing loss), Acoustic trauma

Sourced from: NHS and NICE clinical guidance on hearing and tinnitus

W

Witness statement

A signed account of what someone saw or heard, verified by a statement of truth and used as their evidence. A witness cannot describe what tinnitus sounded like to you — only you experienced it — but they can confirm that you complained of it at the time, which is often the point.

See also: Disease and Illness Protocol, Causation

Sourced from: Statute and civil procedure governing military personal-injury claims

Woodrup v Nicol

The Court of Appeal authority used in Abbott when considering future private treatment costs. Section 2(4) of the Law Reform (Personal Injuries) Act 1948 means NHS availability is disregarded when assessing whether private expenditure is reasonable, but the claimant must still prove that they are genuinely likely to use the private treatment or equipment for which damages are claimed.

See also: Special damages, Hearing aid

Sourced from: Statute and civil procedure governing military personal-injury claims

WPS (War Pension Scheme)

Also called: War Pension · War Disablement Pension

The no-fault statutory scheme for disablement caused or made worse by service before 6 April 2005. There is no general time limit for making a WPS claim after service ends, although evidential rules change after seven years. Conditions caused by service on or after 6 April 2005 generally fall under AFCS, so service spanning the boundary may need closer analysis.

See also: AFCS (Armed Forces Compensation Scheme), 6 April 2005, Crown immunity

Sourced from: War Pension Scheme — current rules and guidance

RemedyBridge is a claims management company, not a law firm, and nothing on this page is legal or medical advice. You never have to pay anyone to apply to the Armed Forces Compensation Scheme or the War Pension Scheme — the free routes are here.