Note 7 of the Coles, Lutman & Buffin Guidelines!

A common request from my instructing solicitors on noise-induced hearing loss claims is to assess the Claimant’s noise immission level, a measure of lifetime noise exposure, excluding daily noise exposure levels below 85 dB as recommended in Note 7 of the Coles, Lutman & Buffin guidelines [1]

In my opinion, the recommendation in Note 7 does not stand up to scrutiny, from an engineering point of view, for a number of reasons as follows:

• Note 7 changes the long-established definition of the lifetime noise immission level from the energy-based quantity defined in the now withdrawn BS 5330:1976 and in the NPL tables of 1973 and 1977[2].
• Note 7 implies that daily exposures below 85 dB are unlikely to cause significant hearing loss. However, there is known to be a small but foreseeable risk at lower levels. Since the Control of Noise at Work Regulations 2005 require certain actions to be taken by employers where the daily exposure is likely to reach or exceed 80 dB, to disregard exposures below 85 dB seems inappropriate.
• Note 7 implies that there is a significant risk to hearing with regular daily exposure at 85 dB but no significant risk with regular daily exposure at 84 dB. In reality, the risk must be similar at these two levels.
• Application of Note 7 means that, for example, exposure for 40 years at 85 dB would give a lifetime noise immission level of 101 dB (insufficient for a diagnosis of noise-induced hearing loss according to the guidelines) while exposure for 40 years at 84 dB would give a lifetime noise immission level of zero. This is clearly ludicrous.

[1] Coles, Lutman and Buffin (2000), Guidelines on the diagnosis of noise induced hearing loss for medico legal purposes, Clinical Otolaryngology, 2000, 25, 264-273.

[2] Robinson D W and M S Shipton (1977). Tables for the estimation of noise-induced hearing loss. NPL Acoustics Report Ac 61 (Second edition) June 1977.