Part 1: A Practical Guide to Diagnosis and Quantification in M-NIHL Claims in the Post-Coles Era

 

In a mammoth 199-page Judgment, Garnham J resolved a number of outstanding issues surrounding military noise-induced hearing loss (M-NIHL) claims. 

Strictly only binding on the cases within the Abbott cohort, the findings are likely to be considered by all involved in M-NIHL claims.  Some issues clearly have relevance for NIHL claims in general. 

In the first of three articles, I shall deal with diagnosis and quantification of M-NIHL. 

The second article will deal with other key causation features arising from Abbott.

The third article will consider quantum.

Diagnosis and Quantification - Overview

The court reminded practitioners that diagnosis of NIHL in any given case is a matter of clinical judgement, albeit guided by diagnostic tools/ methods:

“There may well be cases for which none of the methods is completely appropriate; clinicians and experts cannot entirely substitute the application of their preferred diagnostic tool for individual clinical judgement.” (paragraph 308)

However, I would expect that, as experience shows with application of the Coles guidelines in industrial cases, the further an expert departs from the preferred methodology, the better the explanation that will be needed to justify the same. 

As with Coles, it was not possible for every permutation to be considered in Abbott and so those matters beyond the Judgment may be the subject of future argument.

The Approach to Diagnosis and Quantification
(Chapters 8 and 9)

The rM-NIHL method^[1] is the preferred method for diagnosis

The use of the original Moore M-NIHL guidelines and MLP (18) should not be relied upon in M-NIHL claims. 

CLB/ Coles was not excluded altogether, but the Court held it was ‘not generally suitable’ for military cases.

The rM-NIHL method is the one to be preferred. (paragraph 419).

However, a key reason for rM-NIHL being preferred over Coles is that military noise more frequently/ commonly affects 6 and 8 kHz in a way that industrial noise generally does not (paragraphs 372 and 418). 

It was, though, acknowledged that in military cases the frequency with the greatest hearing loss varies across individuals (paragraph 375).  It appears, therefore, in military cases where the greatest loss is at 4 kHz (so similar to typical industrial NIHL - which may be a minority), then Coles may still be a useful method in such cases.

  

The MLC method^[2] of quantification is to be preferred - but with important adaptations

The MLC method of quantification was preferred over LCB (paragraph 459 - 464 and 521).

However, it is important to recognise that whilst the use of MLC was preferred, this was subject to important adaptations.

So, the method for quantification of hearing loss is:

1. The Appropriate Method:

Calculate the degree of M-NIHL using MLC – separately on each ear.

This is as set out in the MLC paper.

2. The Appropriate Percentile:

Of course, individuals’ hearing loss varies from person to person. 

Any method of quantification for NIHL measures an individual’s actual hearing loss, then subtracts the estimated ‘natural’ hearing ability, with any difference being attributed to noise damage. 

Accordingly, placing an individual on the correct percentile is key to this process.

It is a matter of clinical judgment based upon all the available audiometry as to what is the correct percentile to use (paragraph 472 – 476 and 522). 

If someone is on a higher percentile, this means their ‘natural’ hearing loss should be considered to be lower, and so the NIHL element is increased, and vice versa.

The matter of percentiles is likely to be especially important in low loss cases and where de minimis may be raised (see below). 

Since no specific method was given for how the percentile ought to be chosen, this may be an area for future judicial consideration.

 

Baseline Correction

This important element appears to have received little general attention - but it should do.

A 2.4 dB deduction across all frequencies (1 – 8 kHz) is required owing to the ISO 7029 2017/ 2024 dataset used (paragraph 272 – 277 and 472). 

In correspondence with Professor Moore, he has indicated to me that to make the 2.4 dB baseline adjustment to the amount of NIHL (the quantum), 2.4 dB should be removed from figures previously calculated.

So NIHL previously calculated by MLC to be 10.5 dB will become 8.1 dB after the 2.4 dB baseline adjustment. 

I have access to Professor Moore’s own updated (post-Abbott) MLC calculator, and so an example is shown below:

This is an important connection to make to previous medical reports.

3. The Appropriate Frequencies

The frequencies to be considered as the ‘baseline descriptor’ are 1, 2 and 3 kHz, though 1, 2 and 4 kHz can also be considered especially where speech to noise difficulty is a feature (paragraph 497 – 499 and 523).   

A mean loss across the chosen 3 frequencies should be calculated.

4. Asymmetry

This considers how to calculate the overall effect of any NIHL when the NIHL loss may be different between the ears, or indeed not present at all in one ear.

It was found that much military noise exposure is asymmetric – which would result in asymmetric NIHL.  It does not cause the difficulties found in industrial cases (Coles, note 11). 

Indeed asymmetry is ‘common, if not the norm’ in military cases (paragraph 380).

The most obvious example is the ‘head shadow effect’ – so that the right ear is subject to less noise exposure than the left - when firing a rifle from the right shoulder.

Indeed, from my own recollection I can distinctly remember an early field-firing exercise on Dartmoor, and getting short-term dullness and ringing isolated to the left ear after firing only a few rounds of ammunition.

The court found that the overall degree of NIHL (by which the likely impact on a claimant can be judged) is then calculated bilaterally using the formula (paragraphs 518 – 520 and 524):

(4 x better ear) + (1 worse ear)

______ 

5

So for someone with a loss of 10 dB in one ear and 5 dB in the other ear, the calculation would be:

 

(4 x 5 dB) + (1 x 10 dB)

______

5

= 6 dB binaural loss

 

However, it was acknowledged that in cases with NIHL in only one ear this calculation may not capture all the problems that an individual may have (paragraph 509).  

In such cases, the expert should set out why the 4:1 ratio may not be fully appropriate, and consider a different approach.   The full extent of the disability will need to be explained (paragraph 520).

Although the Judgment did not set out any specific examples, these may include:

a. That the Claimant would not notice his/her hearing loss but for the NIHL (or at least would not have noticed as early).

b. Specific difficulties in hearing from one side in a particular environment(s) - whilst driving a car, whilst in an office/meeting, using a phone.

c. That a claimant experiences specific difficulty in background noise, including, but not limited to cocktail parties!

d. That there are specific difficulties in the ability to detect speech (paragraph 680).

Further, in cases where rM-NIHL results in a ‘false’ result on one ear using the rM-NIHL calculations, but the MLC calculations in that same ear result in a positive degree of quantum Professor Moore has indicated to me in correspondence that this positive quantum should be used when considering the overall NIHL (so when applying the 4:1 ratio).  On the balance of probabilities that ear does have NIHL, but not enough to meet the rM-NIHL criteria.

It should be said that this last point was not a feature of the Abbott judgment itself and so had not been subject to counter-argument/ judicial consideration.

De Minimis (Chapter 13)

De minimis arguments had seemingly fallen out of vogue in general NIHL cases in recent years, but they were reignited in Abbott (paragraph 677 – 681). 

The court found that the starting point is that a loss of less than 4 dB (over 1, 2 and 3 kHz or 1, 2 and 4 kHz) would be de minimis unless there are other consequences (paragraph 681). 

On a case-by-case basis, determination is required as to whether loss below the 4 dB causes ‘appreciable damage’.

There is clearly overlap with the matters set out above in relation to asymmetry.  If the 4:1 calculation does not capture the actual damage to a claimant, then the medical expert should set out why in as much detail as possible.

Cochlear Synaptopathy/ latency/ acceleration

At present, these concepts remain unproven.  

Reference to them in previous medical reports can therefore be ignored/ removed – at least until further research has been conducted.

Conclusion

Every medical report previously written in NIHL cases ought to be reviewed in light of the above.  Some will require greater amendments than others. 

It is not the case that rM-NIHL or MLC were simply accepted - important caveats were applied.

Part Two:

In the second article I shall consider other key ‘causation’ chapters of the Judgment, including:

1. Tinnitus.
2. General noise exposure in military cases.
3. Military Audiograms.

Part Three - Quantum

1. PSLA.
2. Hearing aids.
3. Loss of Earnings.

With thanks to Paul Woodford, Partner at Sintons Solicitors for reviewing and providing comment on the content. 

About the Author

Jim Hester is a barrister at Parklane Plowden Chambers, specialising in occupational disease, personal injury and military claims. He is the author of the chapter on noise-induced hearing loss in Munkman on Employer's Liability, and a former Major in the Royal Marines Commandos, having served for a decade before being called to the Bar in 2010. He is recommended in the Legal 500 and Chambers & Partners, and was a member of the Attorney General's Panel of Counsel from 2020 to 2025.

[1] Moore, B. C. J., Lowe, D. A., & Cox, G. (2022). Guidelines for diagnosing and quantifying noise-induced hearing loss. Trends in Hearing, 26, 1–21. https://doi.org/10.1177/23312165221093156

[2] Moore, B. C. J., Humes, L. E., Cox, G., Lowe, D., & Gockel, H. E. (2022). Modification of a method for diagnosing noise-induced hearing loss sustained during military service. Trends in Hearing, 26, 1–9. https://doi.org/10.1177/23312165221145005

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