Over the past year, researchers at the University of Manchester, have been observing the impact of recreational noise exposure (e.g. use of personal audio devices at high volumes and attendance at concerts, bars, clubs, sporting events, etc.) on younger generations, amid concerns that the extent of hearing damage in this demographic has been ‘underestimated’.[i]
N.B. whilst the Health and Safety Executive (HSE) strongly recommends that no audience members during the course of any event are exposed to equivalent continuous sound levels in excess of 107 dB(A) Leq, nor sound pressure levels in excess of 140 dB(C), there is no specific legislation that sets out exposure levels and daily noise dosimetry for audiences, i.e. there is no occupational upper action level [85 dB(A) Lep,d] equivalent.[ii]
Indeed, the World Health Organisation (WHO) projected, as of 1 March, that around 1.1 billion young people (those aged between 12 and 35 years) were at risk of noise-induced hearing loss (NIHL), owing to prolonged recreational noise exposure.[iii]
To further investigate this claim, a Manchester Centre for Audiology and Deafness team, led by Research Associate, Samuel Couth, examined the hearing function of 123 young adults (between the ages of 18 and 27) by several different metrics, including:
- Pure-tone audiometry (PTA);
- Extended high-frequency (EHF) thresholds;
- Otoacoustic emissions (OAE);
- Auditory brainstem responses (ABR);
- Speech perception in noise (SPiN); and
- Self-reported tinnitus, hyperacusis and hearing in noise difficulties.
Before doing so, the participants (76 of whom were musicians and 47 of whom were not) were asked to provide a detailed account of their personal lifetime noise exposure, i.e. how often they attended clubs and concerts (for musicians, there was also work-related exposure) and how loud they perceived these settings to be.
The key question, here, was whether early career musicians were more likely to demonstrate early signs of sub-clinical hearing damage (imperceptible with PTA), such as cochlear synaptopathy (a loss of synapses between inner ear hair cells and spiral ganglion neurons), than non-musicians.
Full results were published in the journal, Hearing Research, last month.[iv]
Firstly, it became apparent to the study authors that both the musicians and the non-musicians had reported similar amounts of lifetime noise exposure when interviewed. Work-related exposure only contributed towards a small fraction of their overall exposure, meaning that recreational noise exposure was the predominant source.
Secondly, it was established that every participant produced PTA results that were indicative of ‘clinically normal hearing’, i.e. hearing threshold levels were not significantly elevated.
However, those who reported the highest levels of lifetime noise exposure were worse affected by sub-clinical outer hair cell (OHC) dysfunction, as measured by distortion product OAE. They also had poorer conduction of noise stimuli along the auditory brainstem pathway (dubbed ‘increased ABR wave V latency’), as measured by ABR testing, additional to more frequently experienced hyperacusis (defined as ‘an abnormal sensitivity to everyday sound levels or noise’).
It was concluded that the noise-induced hearing impairments present in the study group could constitute so-called ‘hidden hearing loss’ and could also explain the sequelae of cochlear synaptopathy, which was not associated with lifetime noise exposure in this particular study.
In a follow-up article, written for The Conversation (and subsequently published on the University website), Mr. Couth divulged that:
‘Crucially, what our research reveals is that all young adults who engage in noisy recreational activities without using hearing protection are at risk of hearing damage. It’s likely that without a change in our attitudes towards noise exposure and hearing protection, we will see many more people presenting with hearing problems later in life’.
Nonetheless, levels of recreational noise exposure for young adults would be expected to decrease with age, which would theoretically cause lifetime noise exposures of non-musicians to diverge from musicians (on the assumption that they have long careers of high-level occupational exposures).
Acknowledging this, the Manchester University researchers called for more analysis on ‘the effects of noise exposure on hearing function longitudinally’, on the basis that ‘it may be possible to determine whether musicians are more susceptible to hearing problems, and thus develop interventions to protect hearing longevity’.
[i] Samuel Couth, ‘Hearing loss: early signs of damage in young adults who regularly attend loud clubs and concerts’ (2 July 2020 University of Manchester) <https://www.manchester.ac.uk/discover/news/hearing-loss-early-signs-of-damage-in-young-adults-who-regularly-attend-loud-clubs-and-concerts/> accessed 18 August 2020.
[iii] ‘Deafness and hearing loss’ (1 March 2020 WHO) <https://www.who.int/news-room/fact-sheets/detail/deafness-and-hearing-loss> accessed 18 August 2020.
[iv] Couth S et al., Investigating the effects of noise exposure on self-report, behavioral and electrophysiological indices of hearing damage in musicians with normal audiometric thresholds. Hearing Research (2020) <https://www.sciencedirect.com/science/article/pii/S0378595520302926/pdfft?isDTMRedir=true&download=true> accessed 18 August 2020.