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Isolated 6kHz notching and strategic issues in deafness claims

Humphreys v Tepgold Ltd
Manchester County Court – HHJ Main QC
11 July 2016

Carol Purang of DWF’s disease team reports on this recent Noise Induced Hearing Loss case in which she acted on behalf of the defendant. The claimant, who was relying upon notching in his audiogram at 6 kHz only, discontinued his claim part way through the trial.


The claimant alleged excessive noise exposure whilst working as an industrial painter with the defendant from 1968 to 1973. The defendant had long ceased trading and had no evidence to offer on breach of duty.

Exposure and Breach of Duty

A single joint engineer was instructed. The claimant’s statement was lacking detail but doing the best he could the engineer estimated a noise immission level at 100.1dB taking account of exposure elsewhere.

Medical Causation: Diagnosis of NIHL

There was no doubt that the claimant had a degree of hearing impairment. There was dispute as to whether noise exposure had caused any part of that impairment. The claimant relied upon notching in his audiogram at 6 kHz only. Whilst that satisfied criteria R3a of the Coles Lutman Buffin Guidelines the defendant contended that diagnosis on that basis was far too mechanistic and ignored medical literature on the significance or otherwise of isolated 6 kHz notching.

The claimant relied upon evidence from Mr Mian and the defendant relied upon evidence from Mr Jones.

The defendant’s case was that:

(a)   6 kHz is a notoriously difficult frequency at which to obtain accurate hearing measurements;

(b)   6 kHz is affected by conditions other than noise and isolated notches are unreliable as an indicator of noise damage;

(c)   4 kHz is the frequency most often affected by noise and to the greatest extent. In this case at 4 kHz there is no notch or bulge;

(d)   At anchor points of 1 & 8 kHz (frequencies affected to a small extent if any by noise) the claimant was on the 25th centile for his hearing. His hearing at 3 and 4 kHz was actually better than predicted for a man of his age at this centile.

The initial report from Mr Mian was based on a 2013 audiogram which, he said, showed notches at 6 kHz in both ears. The validity of the audiogram had been challenged and a repeat audiogram was performed in 2014. This had notching at 6 kHz on one side only and was broadly consistent with the defendant’s audiogram from 2015.

In Part 35 questioning pre-trial on the 6 kHz issue many of Mr Mian’s answers were non-responsive and at trial he was cross examined extensively on the issue. He gave the appearance of being dogmatic in his views and defensive in his approach. This was despite a warning from the judge to Mr Mian that he needed to seriously consider his responses as the judge was going to have to determine his credibility as an expert witness.

Outcome and comment

After a full day of evidence from both the claimant and Mr Mian, the claim was discontinued without the defendant’s expert Mr Jones having to give evidence.

Interestingly, on conclusion of the action, the trial judge HHJ Main QC commented that having dealt with numerous NIHL cases he does not believe them to be straightforward. He added that the CLB Guidelines are just that: not all cases fall within the Guidelines, and those that do not, need to be considered on their own facts, and outside the Guidelines if required.

This case demonstrates there is clearly merit in actively investigating and challenging cases with isolated 6 kHz notching. There is an abundance of medical literature citing how unreliable isolated 6 kHz notching is for a diagnosis of NIHL. It is important to ensure that defence expert reports cite such literature.

On this occasion the claimant chose not to continue with the trial having heard their own expert try to justify a diagnosis of noise loss based on isolated 6 kHz notching. There will no doubt be future trials on this issue with perhaps stronger claimant evidence and further judgments will emerge. For now it remains an area in which an active defence can be maintained.


For further information, please contact Carol Purang, Associate on +44 (0)161 603 4971 or at carol.purang@dwf.law

This information is intended as a general discussion surrounding the topics covered and is for guidance purposes only. It does not constitute legal advice and should not be regarded as a substitute for taking legal advice. DWF is not responsible for any activity undertaken based on this information.