Hearing Loss Onset 25 Years Post-Noise Exposure: Harte v Hawker Siddeley Dynamics Ltd & 2 Ors (Wigan County Court, 2018)

In the case of Harte v Hawker Siddeley Dynamics Ltd & 2 Ors (Wigan County Court, 2018), an engineer, employed for a total period of 30 years, was unsuccessful in pursuing a NIHL claim against 3 defendants, arguing that exposure to excessive noise in the course of his employment was the cause.

The 1st and 2nd defendants reached settlement with the claimant pre-trial. However, the 3rd defendant contested the claimant’s claim on medical causation.

The claimant worked for the 3rd defendant from 1980 to 1986, a period of 6 years. For the first 5 years, the claimant was posted in a workshop with 40 employees. He then spent his final year in a different workshop, among just 7 employees.

His job entailed the service and repair of switchgear systems and motors. He used ‘a compressed air nut gun, disc grinder drills and hammers, in close proximity to other fitters, 8 hours a day, 5 days a week, and most Saturday mornings as overtime’.

The claimant was not supplied with hearing protection and was given no advice on health and safety. As such, breach of duty was conceded.

The claimant first noticed his hearing loss in 2012, aged 72. From this point onwards, the claimant noticed ‘markedly worse’ hearing.

Consultant ENT surgeons, Arvind Arya and Philip Jones were instructed on behalf of the claimant and defendant, respectively, while Consultant acoustic engineer, Mike McLoughlin was employed as a single joint expert.

Mr McLoughlin measured the workplace Noise Immission Level (NIL) at 105 dB(A), with noise exposure ranging between 93 and 107. Claimant counsel argued that the NIL was up to 113 dB(A) and no lower than 100 – the minimum noise exposure such as to expose the claimant to a risk of NIHL.

In a Joint Medical Statement, both the claimant and defendant experts agreed that:

‘(i) Mr Harte was suffering from some age associated hearing loss (“AAHL”) and (ii) that noise induced hearing loss (“NIHL”) is “irreversible” and neither occurs nor progresses in the absence of continued exposure without adequate protection and (iii) that the Claimant would benefit from hearing aids’.

In spite of joint medical advice, the claimant refused to wear hearing aids.

Audiometric testing was conducted twice, firstly in 2015 and secondly in 2017. Mr Recorder Parrington accepted the 2015 audiogram as the more relevant set of results, as less time had elapsed since the alleged onset of hearing loss.

Mr Arya noted bilateral, sensorineural, mildly asymmetrical hearing loss, which was worse at high frequencies. He observed a downward notch at 4 kHz. In the right ear, hearing loss was at least 10 dB greater at 3, 4 and 6 kHz thresholds than at 2 kHz. In the left ear, hearing loss was at least 10 dB greater at 4 and 6 kHz thresholds than at 1 and 2 kHz.

Referring to the CLB Guidelines 2015, the claimant’s expert observed high frequency sensorineural hearing impairment, fulfilling R1; a history of continuous exposure to noise, likely fulfilling R2(a); and a downward notch in both ears in the 3 to 6 kHz range (4 kHz), fulfilling R3.

Mean hearing loss at 1, 2 and 3 kHz was 26.7 dB in the right ear and 29.4 dB in the left ear. With AAHL (Presbycusis) for a 75 year old being 16.7 dB, mean NIHL was calculated at 12.7 dB. As such, Mr Arya diagnosed the claimant with NIHL due to excessive noise and AAHL.

Counsel for the defendant questioned Mr Arya on an additional 20 dB notch at 1 kHz, but he could not account for this. Questions were also raised over the 25-year period between the cessation of noisy employment with the 3rd defendant and the alleged date of hearing loss development. Mr Arya accepted that hearing loss could be idiopathic, accounting for 2.5 dB of the original 12.7 dB NIHL calculation. His NIHL calculation was therefore reduced to 10.1 dB.

Counsel for the claimant submitted that, in terms of hearing loss of 2, 3 and 4kHz, which they considered to be the ‘critical frequencies’, the claimant’s hearing loss could be calculated at 8 dB.

Mr Jones, on the other hand, calculated the claimant’s NIHL at 3.3 dB, as argued by defendant counsel at trial.

An average of both expert NIHL calculations (10.1 dB and 3.3 dB) gave a figure of 6.7 dB. Mr Arya sought to argue that any loss above 4 dB would be ‘significant’ and therefore actionable. It was claimant counsel’s argument at trial that any loss above 6 dB was compensatable.

By contrast, Mr Jones considered that a 3 dB loss would be ‘insignificant’ and therefore de minimis.

At trial, counsel for the defendant referred to the McShefferty Papers, which were examined in edition 233 of BC Disease News (here). McShefferty submitted that losses below 5 dB are barely perceptible and have no noticeable effect on speech in noise. The defence also relied on papers written by Lacroix and Harris and by Aniansson, which ‘indicate that a loss of 50dB at 4 kHz and above causes a “decrease of just under 1% in the ability to perceive speech in noise…”’

Mr Jones was also of the opinion that the length of delay could not lead to a positive NIHL diagnosis:

‘... any reasonable audiogram is of doubtful validity in trying to diagnose NIHL which would have been present in full over 30 years’.

In the 2-year period between the 1st and 2nd audiometric testing, Mr Jones stated that hearing loss progression could not be attributed to noise exposure. Further, he argued that the difference between the right and left ears in testing was ‘not acceptable for symmetrical exposure’, especially at noise sensitive frequencies. He was of the mind that asymmetry was an indicator that NIHL was ‘less likely’, whereas Mr Arya believed that ‘asymmetrical loss does not preclude a person from having noise related hearing loss’. What is more, Mr Jones argued that that the claimant’s notch at 1 kHz could not be noise-related.

The defendant’s medical expert therefore concluded that:

‘... perhaps it would be equitable to conclude there is a minor NIHL present which he has never noticed and which on objective criteria would not be judged as significant’.

In coming to his decision, the Recorder had ‘no doubt that the assessment as to NIHL has not been made easier by 2 factors namely (i) the lapse of time between 1986 when exposure ceased to 2012 when the Claimant first noticed a hearing loss, more than 25 years later, and (ii) the onset of AAHL as the Claimant entered his later years’.

He found in favour of the defendant and Mr Jones, on causation. At paragraphs 45 to 49, he reasoned:

‘In my judgment, I find that noise exposure during the period 1980 – 1986 was such as to cause the Claimant a noise induced hearing loss; the engineer’s evidence is that exposure to noise exceeding the limits for which hearing protection is required occurred.

It is clear however that the Claimant was not aware of any loss, whether NIHL, age related loss or idiopathic loss, before April 2012, that being more than 25 years after the noise exposure ceased. Furthermore, there is no medical evidence which purports to demonstrate such a loss before 2012.

I accept that the effect of noise exposure may not manifest itself until some years after the cessation of exposure. I accept that the audiogram of 2015 exhibits a notch of 4 kHz in both ears, that being indicative of NIHL but also there is a notch of 1 kHz which is agreed is not indicative of NIHL. I am also satisfied that the 2015 audiogram demonstrates asymmetry more marked in the noise sensitive frequencies which makes bilateral NIHL less likely.

However, I find it a fact that Mr Harte’s hearing loss for the period 2012 – 2015 (and beyond) can substantially be ascribed to a non-noise, age related loss. It is unfortunate that Mr Harte has failed to act on the medical opinion of the experts to obtain and use hearing aids which these days can be obtained free of charge on the NHS which are both advanced in technology and are unobtrusive – there seems little doubt that his quality of life would be changed for the better, however that must be his choice.

On balance, I find that having regard to the lapse of more than 25 years, the evidence as to advancement of non-noise loss, particularly age-related loss, the asymmetry demonstrated within the audiograms and the Claimant’s own perception of hearing loss, that Mr Jones’ opinion is to be preferred. Such loss of hearing as can be ascribed to noise exposure was not in my judgment sufficient as to be described as significant and such diminution in the Claimant’s hearing as was caused by exposure to noise did not make the Claimant’s ability to hear appreciably worse’.