What Is rM-NIHL? The Military Hearing Loss Diagnostic Method Explained

It was developed specifically because hearing damage associated with military noise does not always look like the traditional pattern seen after years of steady industrial noise.

Military personnel may be exposed to weapons fire, artillery, explosions, aircraft, helicopters, armoured vehicles and other intense or impulsive sounds. Those exposures can produce audiometric patterns that do not fit neatly into the conventional "4 kHz notch" model traditionally used in occupational hearing-loss cases.

The judgment repeatedly emphasised that diagnostic methods are guidelines and that the whole clinical picture must be considered. There is also an important development since Abbott: new peer-reviewed research published later in 2026 found that the original rM-NIHL method was not optimal when applied to men aged 61–80, and proposed a separate method, M-NIHL60+, for that older group.

The short version

• rM-NIHL is a military-specific diagnostic method for noise-induced hearing loss.
• The "r" refers to a revised version of the earlier M-NIHL method.
• It uses the pattern of hearing thresholds on an audiogram together with age-related hearing expectations.
• It allows military NIHL to be identified without requiring the classic 4 kHz notch seen in many industrial-noise cases.
• It gives particular importance to hearing at 3, 4, 6 and 8 kHz.
• Abbott concluded that rM-NIHL should be preferred over CLB in military NIHL cases.
• Abbott did not say that a positive rM-NIHL result automatically proves causation.
• False positives remain possible.
• The exact published sensitivity and specificity figures should not be treated as precise probabilities for an individual veteran.
• The original rM-NIHL validation data were based on men aged 60 or younger.
• Abbott therefore said the method should be used cautiously for women and older men.
• New peer-reviewed research published after Abbott has now tested men aged 61–80 and found the original rM-NIHL method had high sensitivity but poor specificity in that group.
• That newer study proposed M-NIHL60+ as a potentially better-performing method for older men.
• Neither rM-NIHL nor M-NIHL60+ determines whether somebody has a valid legal claim.

What does rM-NIHL stand for?

The term is shorthand for the revised military noise-induced hearing loss diagnostic method.

The method followed an earlier approach known as M-NIHL, developed by Professor Brian Moore specifically to investigate hearing loss associated with military noise. The original M-NIHL method was published in 2020.

A revised method was then developed and published in *Trends in Hearing* in 2022. That revised version became known as rM-NIHL.

The aim was to improve the balance between sensitivity — identifying people who genuinely have NIHL — and specificity — correctly identifying people who do not.

Why was a separate military NIHL method developed?

Traditional medico-legal diagnosis of occupational NIHL in the UK has often relied on guidance known as CLB, named after Coles, Lutman and Buffin. CLB was developed principally around conventional occupational noise — repeated exposure to relatively steady broadband noise in workplaces such as factories.

Military noise can be very different. It may include:

• rifle fire;
• machine guns;
• artillery;
• mortars;
• explosions;
• blast;
• aircraft;
• helicopters;
• armoured vehicles;
• engineering machinery;
• combinations of continuous and impulsive noise.

The audiometric pattern associated with such exposure can therefore be more variable. Abbott concluded that military NIHL can occur without the classic CLB notch or bulge and noted that military noise commonly affects hearing at 8 kHz, which can disguise or erase a conventional notch.

The Court also accepted that military impulse noise tends to produce a different and more variable audiometric pattern from steady-state noise. That was a major reason for preferring a military-specific approach.

What is the CLB method?

The CLB guidelines were published in 2000 for medico-legal diagnosis of NIHL. In simplified terms, they look for:

• sufficient high-frequency hearing impairment;
• sufficient potentially hazardous noise exposure;
• and an audiometric notch or bulge consistent with noise damage.

The traditional notch is often centred around approximately 3 kHz, 4 kHz or 6 kHz.

CLB has been widely used in ordinary occupational hearing-loss litigation. But Abbott concluded: CLB is not generally suitable for military cases.

That does not make CLB scientifically worthless. It means the Court considered it insufficiently suited to the particular patterns and exposures found in military NIHL.

How is rM-NIHL different?

rM-NIHL does not require every case to display a conventional 4 kHz notch. Instead, the method allows the audiometric evidence to satisfy military NIHL criteria in more than one way.

Broadly, it looks for evidence of high-frequency hearing impairment, and then either:

• a sufficiently large notch or bulge when hearing is compared with what would be expected from age; or
• sufficiently excessive high-frequency hearing loss at 4, 6 and 8 kHz compared with age-associated expectations.

That second route matters. Military noise can substantially affect 8 kHz. If 8 kHz has also deteriorated, the traditional "recovery" beyond a 4 or 6 kHz notch may disappear. A method requiring a visible classic notch could therefore miss some genuine military noise damage.

Which frequencies matter in rM-NIHL?

The method places particular emphasis on the higher frequencies: 3 kHz, 4 kHz, 6 kHz and 8 kHz.

It also considers lower-frequency thresholds when determining whether there is a high-frequency hearing impairment. This is one reason 8 kHz can be particularly important in military cases.

Our guide to how to read a military audiogram explains these frequencies and hearing thresholds in more detail.

What does rM-NIHL compare hearing against?

A person's hearing naturally tends to change with age. So simply finding that an older veteran has worse high-frequency hearing than a young person proves very little.

rM-NIHL uses age-associated hearing-loss data to ask a more useful question: Is this person's high-frequency hearing worse than would reasonably be expected from age alone?

The method uses reference data from ISO 7029 for age-associated hearing thresholds. Abbott concluded that the updated ISO 7029:2017/2024 data should be preferred for diagnosis and quantification.

Age adjustment does not "remove ageing" with mathematical certainty. People of the same age do not all have identical hearing. The reference data describe a population distribution, not what one individual person's hearing would definitely have been without noise. That uncertainty is one reason clinical judgement remains essential.

What are Mag(Notch) and Mag(ExcessHF)?

The revised method introduced two technical measurements.

Mag(Notch)

This measures the magnitude of an audiometric notch or bulge after allowing for the hearing changes expected with age. The 2022 rM-NIHL paper selected a threshold of 14.5 dB for this part of the method. The calculation can examine patterns centred around 3, 4 or 6 kHz relative to 8 kHz.

Mag(ExcessHF)

This looks at average hearing loss across 4 kHz + 6 kHz + 8 kHz and compares it with the average expected from age. The published threshold selected for this criterion was 19 dB above the corresponding age-associated expectation.

Can I enter my audiogram into the formula myself?

You can understand the numbers. You should not treat the result as a medical or legal diagnosis.

The method is more than numbers in → claim yes/no.

Abbott stressed that the suggested diagnostic methods are guidelines and require consideration of the whole clinical picture. Relevant matters can include:

• military noise exposure;
• type and intensity of noise;
• hearing protection;
• entry audiograms;
• serial military audiograms;
• modern diagnostic audiometry;
• age;
• medical history;
• ear disease;
• medication;
• family history;
• civilian occupational noise;
• recreational noise;
• asymmetry;
• conductive hearing loss;
• tinnitus;
• possible alternative causes.

A calculation cannot perform that clinical reasoning.

What did Abbott actually decide about rM-NIHL?

The Court's conclusion was clear. Mr Justice Garnham held that:

• the original M-NIHL method should not be relied upon in medico-legal work;
• the MLP(18) method should not be relied upon in medico-legal work;
• CLB is not generally suitable for military cases;
• rM-NIHL is the diagnostic method to be preferred.

The Court then added something equally important: a proper diagnosis depends on the careful application of each element of the rM-NIHL test.

So the judgment should not be reduced to "Abbott says rM-NIHL wins." The Court preferred the method while also discussing its weaknesses in considerable detail.

What is sensitivity?

Sensitivity asks: Of the people who really have the condition, how many does the method correctly identify? A highly sensitive method misses relatively few genuine cases.

In the 2022 study used to develop rM-NIHL, when a positive result in either ear was sufficient to classify the individual as positive, reported sensitivity was approximately 98%. When a positive diagnosis was required in both ears, reported sensitivity was approximately 76%.

Those numbers sound precise. Abbott warned against treating them that way.

What is specificity?

Specificity asks: Of the people who do not have the condition, how many does the method correctly identify as negative? Higher specificity means fewer false positives.

In the 2022 rM-NIHL development data:

• an either-ear diagnosis had specificity of approximately 63%;
• a both-ear diagnosis had specificity of approximately 95%.

Again, these are study estimates, not individual probabilities.

Does 63% specificity mean there is a 37% chance my diagnosis is wrong?

No. This is a very important statistical distinction.

A specificity of 63% in a particular control dataset does not mean "every person with a positive result has a 37% chance of not having NIHL."

The chance that a positive result is genuinely correct depends on other matters, including how common the condition is in the population being assessed and how carefully alternative causes have already been excluded. This is known as positive predictive value, or PPV.

Abbott considered this issue in detail. The Court ultimately concluded that little weight should be attached to exact sensitivity or specificity figures and described them as no more than ballpark estimates. It considered PPV more useful, but not decisive.

Most importantly, the Court said all the suggested diagnostic methods depend on audiograms and are intended as guidelines only. The whole clinical picture remains necessary.

What is a false positive?

A false positive occurs where a diagnostic method produces a result consistent with NIHL in somebody who does not actually have noise-induced hearing loss.

This matters because audiometric features associated with noise exposure can also occur in people who have not had harmful noise exposure. The experts in Abbott agreed that the audiometric indicators used by CLB, M-NIHL and rM-NIHL can occur in people without NIHL.

Why can somebody without NIHL meet an rM-NIHL criterion?

Human hearing varies. Some people naturally have poorer high-frequency hearing than the population median. Others may have:

• idiopathic sensorineural hearing loss;
• genetic susceptibility;
• another ear disorder;
• non-military noise damage;
• medical causes;
• a combination of different causes.

Some of these conditions can produce audiogram shapes that resemble noise damage.

Abbott specifically considered idiopathic hearing loss — hearing loss where no definite cause can be identified. The judgment said that possibility must be considered by the diagnosing clinician rather than ignored simply because the rM-NIHL criteria are satisfied.

Does a positive rM-NIHL result prove military causation?

No. A positive audiometric indication is one part of the causation assessment.

The medical examiner still needs to decide whether the individual's hearing is worse than it probably would have been without the relevant noise exposure. That involves considering noise history + audiogram + age + medical history + alternative causes.

A person can satisfy an audiometric criterion and still require further investigation before military NIHL can properly be diagnosed.

Does a negative rM-NIHL result prove I do not have military NIHL?

It should not be treated as an automatic legal rejection. Diagnostic methods have limitations.

The effect of a result can depend on:

• whether all required frequencies were tested;
• whether the audiogram is reliable;
• whether historic data are available;
• whether one or both ears are involved;
• age;
• sex;
• unusual exposure patterns;
• other clinical features.

An ENT or audiology expert should interpret the result in context.

Why are entry audiograms important?

If somebody had an audiogram when they entered the Armed Forces, it may provide evidence of their hearing before substantial service noise exposure occurred. That can be particularly useful.

For example, if an entry audiogram showed unusually poor hearing at a frequency before the relevant military exposure, that may affect an interpretation that would otherwise be made using age-population averages.

Abbott expressly recognised that audiometric characteristics on entry to the Armed Forces may sometimes displace a conclusion that would otherwise follow from the application of rM-NIHL. That is another reason population averages cannot replace individual evidence.

What if my old military audiogram does not contain 8 kHz?

This can matter. rM-NIHL makes significant use of 8 kHz. But not every historic military screening audiogram recorded that frequency.

If 8 kHz was not tested, the missing result should not simply be invented from a later audiogram. Abbott considered the dangers of retrospectively reconstructing missing historic audiometric data.

Our guide to how to read a military audiogram explains the 8 kHz issue in more detail.

What about the 6 kHz result?

6 kHz also requires care. Abbott examined evidence that certain TDH39P headphones can produce variable measurements at 6 kHz.

The Court rejected an automatic rule of deducting 6 dB from every relevant measurement. Instead, where the precise 6 kHz result could affect diagnosis or quantification, the ENT expert should approach it cautiously and assess it in the context of the audiometric series.

Again: context rather than automatic arithmetic.

Does rM-NIHL work for women?

This is an area where the limitations need to be stated plainly.

The datasets used to develop the 2022 rM-NIHL method consisted of men. During Abbott, the experts agreed that the method had not been evaluated specifically in a population of women. The Court therefore said rM-NIHL is limited by age and sex.

That does not mean women cannot develop military NIHL. It does not mean a female veteran cannot pursue a claim. It means the scientific validation of this particular diagnostic method does not have the same evidential foundation for women. That distinction is important.

What age was rM-NIHL originally developed for?

The original rM-NIHL development datasets were composed of men aged 60 years or younger. Abbott therefore recorded that the method should be used cautiously for men over 60.

At the time the judgment was handed down on 24 April 2026, the Court recorded that the experts were not aware of a published evaluation of rM-NIHL restricted to men over 60.

That position has now changed.

Important 2026 update: rM-NIHL in men aged 61–80

A peer-reviewed study published after the Abbott judgment has now examined the use of rM-NIHL in older men. The researchers assessed 329 military noise-exposed men aged 61–80, and 123 non-exposed men.

When the original rM-NIHL method was applied to this older group, it demonstrated high sensitivity but poor specificity.

In plain English: it identified a high proportion of noise-exposed individuals, but it also produced too many positive results among the non-exposed comparison group.

The researchers modified the rM-NIHL criteria, which improved the balance between sensitivity and specificity, but the overall diagnostic performance remained only moderate. They therefore developed another method: M-NIHL60+.

What is M-NIHL60+?

M-NIHL60+ is a newly developed diagnostic method intended specifically for men aged 61–80.

Rather than relying on the original rM-NIHL criteria, it uses a weighted average of age-corrected hearing thresholds across frequencies from 1 kHz to 8 kHz.

In the 2026 study, M-NIHL60+ produced a better overall diagnostic performance than the original rM-NIHL method, and than the modified rM-NIHL criteria tested for the older group.

This is an important scientific development. It is also very new.

Did the High Court approve M-NIHL60+?

No.

Abbott was handed down in April 2026. The M-NIHL60+ research was published afterwards. The Court therefore could not have considered it.

As at 24 August 2026, the correct distinction is:

• Abbott: rM-NIHL is the diagnostic method the High Court preferred in the generic military NIHL litigation.
• Later scientific research: the original rM-NIHL method appears less suitable for men aged 61–80, and M-NIHL60+ has been proposed as a better-performing method for that group.

Those statements are not contradictory. One describes the judgment. The other describes subsequent scientific evidence. A source-checked military hearing site should explain both.

Does M-NIHL60+ now replace rM-NIHL legally?

That conclusion should not be made from the research paper alone. A newly published scientific method does not automatically amend an existing High Court judgment.

How the later research should be used in litigation may require medical expert evidence, legal argument or subsequent judicial consideration.

For an older veteran, however, it would now be incomplete to discuss rM-NIHL without acknowledging the newer age-specific research.

What about veterans aged exactly 60 or 61?

The research groups use age boundaries because studies require defined populations. They should not be misunderstood as suggesting that human hearing suddenly changes on a birthday.

The original rM-NIHL method was developed using men aged up to 60. The later research specifically investigated men aged 61–80. How the evidence should be applied to an individual close to that boundary remains a matter for appropriate expert assessment.

Does rM-NIHL calculate how much hearing loss the military caused?

Diagnosis and quantification are separate questions.

rM-NIHL is principally concerned with whether the audiometric evidence supports a diagnosis of military NIHL. Once NIHL is diagnosed, a different exercise is required to estimate how much of the person's hearing loss is attributable to noise rather than age or another cause.

Abbott preferred the Moore, Cox and Lowe method for quantification. The Court also stressed that quantification remains dependent on individual clinical judgement and the person's available audiometric evidence.

So: diagnosis of NIHL ≠ quantification of NIHL.

Does an rM-NIHL result tell me how much compensation I should receive?

No. Even where military NIHL is established, compensation is not calculated by simply inserting an rM-NIHL number into a tariff.

Potential damages may depend on matters such as:

• amount of hearing loss;
• frequencies affected;
• tinnitus;
• functional communication difficulties;
• speech-in-noise problems;
• hearing aids;
• employment effects;
• future losses;
• individual circumstances.

Abbott treated these as fact-sensitive questions.

Does Abbott mean an old claim rejected under CLB was definitely wrong?

No.

Abbott's conclusion that CLB is not generally suitable for military cases may justify reconsideration of some medical evidence that depended heavily on CLB. But it does not prove that every previous negative diagnosis was incorrect.

There may still be:

• alternative causes of hearing loss;
• insufficient evidence;
• normal historic audiograms;
• limitation problems;
• Crown immunity issues;
• or another reason why a civil claim is not viable.

Each case needs to be considered on its evidence.

Can rM-NIHL diagnose tinnitus?

No. rM-NIHL is concerned with hearing loss measured through audiometry. Tinnitus is a separate condition.

A person may have:

• military NIHL with tinnitus;
• military NIHL without tinnitus;
• tinnitus without measurable NIHL.

Abbott dealt with tinnitus as a separate generic issue. An rM-NIHL result therefore does not prove or disprove tinnitus.

Is rM-NIHL used by the NHS?

rM-NIHL is principally a military NIHL diagnostic method developed for medico-legal assessment. Routine NHS audiology is concerned primarily with assessing and treating the patient's hearing needs.

A person does not need an rM-NIHL calculation before receiving appropriate healthcare for hearing loss.

If you are concerned about your hearing, seek an appropriate hearing assessment because of your health, not simply because of a compensation claim.

Can rM-NIHL tell me whether I have a legal claim against the MOD?

No. A civil claim involves questions beyond medical diagnosis. These can include:

• dates of military service;
• dates of harmful exposure;
• Crown immunity;
• combat immunity;
• breach of duty;
• limitation;
• causation;
• contributory negligence;
• apportionment;
• damages.

The Matrix also applies to a particular litigation arrangement and should not be confused with the rM-NIHL diagnostic method.

rM-NIHL, CLB, M-NIHL, MLP(18) and M-NIHL60+ compared

Frequently asked questions