More questions than answers for occupational noise experts?

Abbot v Ministry of Defence

On 24th April 2026, the judgment in the test cases around alleged military noise induced hearing loss ("M-NIHL") was handed down by Mr Justice Graham.

This judgment was keenly awaited by claimant and defendant lawyers practising in the field of M-NIHL.

However, it was apparent the judgment was also going to cover a number of issues of wider relevance to noise induced hearing loss (“NIHL”) claims generally, such as onset of tinnitus, latency of damage and audiometry related issues. It is a comprehensive judgment that covers these issues and more, and we can thoroughly recommend that the "Judicial Primer" on agreed facts about hearing and NIHL is read at paragraphs 40 to 115, along with the summary of the various approaches to diagnosis also seen at paragraphs 311 to 327 for anyone not familiar with NIHL claims, or indeed those needing a refresher.

At the outset of this note, it does have to be said that it is not guaranteed that the approach favoured by the Learned Judge in this case will have any application to a case of solely ‘industrial’ noise exposure. There was, after all, a number of references to the fact that the nature of the damage caused to the ear by high intensity impulsive noise (such as gunfire) is different to that caused by steady state broadband noise generally found in industrial environments.

That being said, to assume that to be the case would appear to be risk being a touch naive, not least as many of these arguments first arose in the context of industrial NIHL claims. 

Summary

Our detailed analysis follows below, but in summary the key findings were:-

• Occupational Audiometry 
  • BSA compliant audiometry remains ‘the gold standard’
  • Screening audiograms can be taken as part of the exercise of clinical judgment, with all audiometric evidence considered “as a whole”.
• Datasets
  • The appropriate standard to be used was ISO7029:2017 (as corrected in 2024).
• TDH39 Headphones
  • The customary 6dB adjustment at 6kHz to audiograms when the TDH39 headphones has been used should not be made automatically
• Latency of Hearing Loss/Cochlear Synaptopathy
  • Latency arguments were dismissed
  • Cochlear synaptopathy arguments dismissed
• Tinnitus
  • No firm conclusions on latent tinnitus
  • Each case turns on its facts
  • Will be decided on the length of the delay between the end of the exposure and the start of the tinnitus, and the veracity of the claimant
• De-Minimis
  • A hearing loss of less than 4dB would not be noticeable and, if that measure is taken alone, would be de minimis
  • However, the judgment later on goes on to say “I do not exclude, for example, the possibility that a claimant with a hearing loss measured at less than 4 dB might nonetheless be able to establish that the deterioration of his ability to detect speech amounts to an appreciable loss”.
  • Therefore, cases have to be considered carefully on the evidence presented. 
• Quantification
  • "In my judgment, the inevitable conclusion is that CLB is not a suitable method of diagnosing NIHL in cases where it is possible that the individual was exposed to the sort of noise typically experienced by members of the armed forces."
  • Questions remain where there are mixed military and industrial exposures.

With the above in mind, we follow with a more in-depth analysis of the judgment from the perspective of the occupational noise practitioner.

Occupational Audiometry

This was a key battleground between the claimants and defendant in these test cases (and has been in cases of industrial NIHL for many years). 

The court (unsurprisingly) affirmed that BSA compliant pure tone audiology was the gold standard of audiometric testing but indicated that screening audiograms taken as part of a "consistent pattern" can be used as "part of the exercise of clinical judgment" by medical experts with all audiometric evidence being considered "as a whole" rather than in isolation.

The claimants in Abbot may be unhappy with the outcome that their military audiometry cannot be disregarded but, from a broader perspective, these findings are certainly not unhelpful for industrial NIHL cases.

We have for instance defended a number of cases at trial on the basis of a single occupational test at the end of exposure but showing no evidence of noise damage. The question has to be asked whether, while "audiometry evidence... should, wherever possible, be considered in context and as a whole, rather than in isolation", whether that single occupational test many years ago forms a "consistent pattern" to be used as "part of the exercise of clinical judgment" by medical experts or not?

Cases where there is an "unexplained variation" in occupational tests are also likely to see them given little weight, although that in and of itself appears ground ripe for argument in the future.

Datasets

In a conclusion favourable to claimants, the court ruled that, albeit with a baseline correction of 2.4dB, the appropriate standard to be used was ISO7029:2017 (as corrected in 2024). This appears to be a rather inevitable conclusion given that Professor Lutman accepted in cross examination that the 2024 revision had been accepted by the UK (the 2017 version having been rejected) and that he "wouldn't have any strong objections to using ... either [the 2000 or 2017] version". The judge noted this was a significant change from Professor Lutman's expressed written opinion.

Given the dataset used by Coles, Lutman & Buffin Guidelines was expressly stated by the judge to be "out of date", it is difficult to see how this conclusion would not impact industrial noise induced hearing loss as well. It is not clear how it could be out of date for military NIHL but not industrial NIHL. 

Perhaps the most immediate impact here is that practitioners need to be able (whether by calculator or otherwise) to apply ISO7029:2017 (as corrected in 2024 and with the required baseline adjustment) to their cases and that caution should be exercised before any full-throated defences of "borderline cases".

TDH39 Headphones

In another conclusion that is difficult to see how it can only be applied to military cases, the court ruled that the customary 6dB adjustment at 6kHz to audiograms when the TDH39 headphones has been used should not be made automatically.

It was accepted that the use of TDH39 and TDH39P headphones is liable to produce variable results at 6kHz. However, where the precise measurement at 6kHz could make a difference to the diagnosis or quantification of NIHL, it should be assessed in the "context of the audiometric series of which it forms part" and an adjustment should be made " if [the expert deems] it necessary (to the extent they deem it appropriate"  to ensure it is consistent with the rest of the audiometric series. 

That appears ripe for many arguments moving forwards, not least as the adjustment does not have to be 6dB. 

It is also not clear what is to happen if there is only the one medicolegal puretone audiogram. In the wider context of the judgment, "audiometric series" appears to refer to their being more than one audiogram.

Perhaps, in time, it is going to have to become more common (or even automatic) for defendants to be allowed their own repeat audiology. How that fits with a request for repeat audiology resulting in an exit from fixed recoverable costs remains to be seen.

Latency of hearing loss and Cochlear Synaptopathy

Stated very shortly (and at risk of over-simplification) these issues are related but different.

Latency is the idea that NIHL can accelerate the deterioration of hearing loss after exposure has ceased. It is argued that a person has a "reserve" of hearing and that the noise damage may not be apparent on an initial audiogram but is apparent later, once increasing age has also had chance to act.

Perhaps an example of where this could be contended for is the ex-long term coal miner who shows no evidence of noise damage on his redundancy from the job but who, after another 15 years spent working outside as a postman, has a classical NIHL notched audiogram.

This was a popular argument in industrial NIHL cases 10 or so years ago but was firmly rejected (in a county court case but where the judge on that occasion had the benefit of hearing from Professors Lutman and Moore, along with Mr Zeitoun) on the basis that there was insufficient evidence on the balance of probabilities to say this was occurring. 

In short, the same conclusion was reached here. The door remains open if the scientific evidence ever establishes otherwise.

Cochlear synaptopathy is different from latent damage in that it refers to a form of nerve damage (simplifying matters somewhat) such that a person could experience hearing loss but demonstrating a "normal" hearing test result. 

This was also rejected by the court as it cannot be "definitively be demonstrated, let alone quantified" prior to death. It seems that, even if it can be shown, there is no method for discounting that caused by aging as well.

That argument appears to be stopped in its tracks for the foreseeable future.

Tinnitus

The findings here are another area which appears to have more general application than M-NIHL (although findings were specifically invited by the claimants on the basis of military exposure). 

Industrial NIHL practitioners will be familiar with the debate over whether so called "delayed onset tinnitus" should be considered related to past noise exposure or not. 

It appeared to be an argument that was very much being "won" by claimants as many experts tended to accept the general principle that "the causes of the hearing loss are the causes of the tinnitus", although it never quite disappeared. 

It seems that, while a firm conclusion either way was not reached, the position is perhaps slightly more favourable to defendants than previously. It seems that each case will turn on its facts, those facts being the length of the delay between the end of the exposure and the start of the tinnitus, and the veracity of the claimant. The court is required to be "circumspect" as well.

Of course, this may run into a practical issue in that many of the experts regularly instructed by defendants have for years accepted delayed onset tinnitus in practice. A sudden change in practice on the strength of this decision might invite criticism of their evidence.

De Minimis

This is another argument of which industrial NIHL practitioners will be well familiar. 

The fundamental argument of course is ‘yes, the claimant might have a diagnosable noise injury to their hearing, but the degree of such is so low as to make no appreciable difference to their hearing’. 

It is an argument whose popularity has waxed and waned over the years with a multitude of first instance decisions reaching different conclusions, along with anecdotal evidence that first instance judges who decided one way later altered their views and decided the other in later cases.

Here the ruling at first glance appears very favourable to defendants. Paragraph 679 states:-

"Here, in my judgment, the expert evidence establishes that 4–5 dB of excess loss may be noticeable by some individuals. A hearing loss of less than 4dB would not be noticeable and, if that measure is taken alone, would be de minimis because the claimant experiencing such a loss would not be appreciably worse off."

However, there is a caveat which can perhaps be gleaned from the Learned Judge's own emphasis in this paragraph, with the judgment later on going on to state:-

"...hearing acuity does not equate necessarily or completely with hearing function. There may be other consequences of exposure to noise which do leave a claimant appreciably worse off. ...  I do not exclude, for example, the possibility that a claimant with a hearing loss measured at less than 4 dB might nonetheless be able to establish that the deterioration of his ability to detect speech amounts to an appreciable loss."

It is perhaps helpful for defendants to see the 4dB "cut off" as a trigger to when this argument comes into play, rather than a bright line. 

It is to be expected that where tinnitus is alleged as well, a finding of de minimis loss will be hotly contested on the basis that this alone is something that leaves a claimant appreciably worse off. 

Combined perhaps with the direction to more closely examine delayed onset tinnitus (although note the potential caveat mentioned about that above), perhaps the most that can be said is that medical evidence where a claimant is interviewed in detail by a medical expert (and probably both medical experts) may be vital.  

Diagnosis and Quantification of Military NIHL

Last, but certainly not least, is that the court ruled on the approach to be taken when diagnosing noise induced hearing loss. Evidence was taken from a number of experts but, chief amongst them, were Professors Lutman and Moore, frequent opponents in the past few years in the field of NIHL.

Certain of Professor Moore's methodologies were robustly rejected by the court and we need not concern ourselves with the detail of those here. The key battleground came down to whether the Coles Lutman and Buffin Guidelines from 2000 should be preferred over Professor Moore's revised approach to assessing M-NIHL. In short, emphasising the different nature of the damage in military cases, the court preferred Professor Moore's approach.

At first glance, this would appear to have limited interest to occupational practitioners, particularly given (as noted several times) the difference in the damage caused to the ear from broadband and military noise sources.

However, what about "mixed" cases where claimants have spent some or even many years in the armed forces before moving into a factory environment? Here the judgment says:-

"In my judgment, the inevitable conclusion is that CLB is not a suitable method of diagnosing NIHL in cases where it is possible that the individual was exposed to the sort of noise typically experienced by members of the armed forces." (our emphasis)

That appears to be a firm statement from the High Court (and one likely to be followed in the lower courts) that CLB would have no application in these military cases. But where is the line? Say a claimant has 10 years total exposure, it could reasonably be said that CLB has no application if the split is eight years in the military and two years in a noisy factory? But what about if it is five years each, or one year in the military and nine in the factory? Further litigation to trial and perhaps appeal seems inevitable.

Strategies will have to be carefully considered in these cases. Service records, potentially overlooked in the past by an overly busy practitioner, may now be absolutely vital to obtain as well, with all the delays that entails. 

Industrial NIHL practitioners should also brush up on the M-NIHL methodology of Professor Moore.

On quantification of military cases, the court largely favoured the approach of Professor Moore over that of Professor Lutman in the "LCB" quantification paper. Given the findings on diagnosis, this is perhaps not surprising.

The court did not accept the evidence/approach of Professor Moore uncritically:-

• The suggestion that use of the 50th percentile should be the default was rejected. Medical experts' decisions should be a matter of clinical judgment based on all available audiology
• Quantification should continue to be based on 1-3kHz but metrics that include 4kHz continue to be legitimate where difficulty hearing speech in noise is a prominent feature. 
• The binaural approach to quantification (4 x the better ear + 1 x the worse ear / 5) should continue to be followed with scope for clinical judgment if "the excess loss calculation does not fully reflect the totality of the problems experienced by the claimant". How this fits with the decision on de minimis loss is not clear. An argument over a binaural de minimis loss but a unilateral appreciable loss appears to be an obvious battleground moving forwards.

Conclusions

Boiling this judgment down to its essentials when it is so new and the approach that may now be taken by the county courts when dealing with industrial NIHL claims is not easy to predict. We expect that the approach is likely to alter on a case-by-case basis, at least initially.  

There may also be a ‘sting in the tail’ in that, on the facts, one of the lead claimants saw his case for M-NIHL rejected but he was awarded compensation for noise induced tinnitus. It seems that might be a highly fact specific decision with a specific acoustic traumatic event being able to be pointed to (and a prior agreement as to limitation in the litigation) but it might see arguments raised over noise induced tinnitus when there is no provable evidence of NIHL. It has to be assumed that any of those cases will face severe limitation hurdles, but Section 33 decisions are always somewhat of a lottery for both parties.

The observations above, formulated as they have been in the days following the judgment, may prove to be moot, with a later judgments finding a grand divergence between industrial and M-NIHL as being both necessary and appropriate (although that wholesale approach does not seem likely). The only thing that occupational NIHL practitioners can be sure of is that their jobs have not got any easier as a result of this judgment.