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The diagnosis ‘acoustic shock’ has been made increasingly in the health care industry in recent years. This paper aims to question the validity of acoustic shock as an organic pathological entity.
The experiences of 16 individuals diagnosed as having acoustic shock, within a medico-legal practice, are reviewed.
The commonest symptom was otalgia, followed by noise sensitivity, tinnitus, hearing disturbance and dizziness.
The presence of noise-limiting technology in the workplace, the variation in the nature of the acoustic incident involved (ranging from a shriek, through feedback noise, to a male voice), and the marked variation in the time of symptom onset (following the acoustic incident) all suggest that the condition termed acoustic shock is predominantly psychogenic. Cases of pseudohypacusis indicate that malingering is a factor in some cases. Clusters of acoustic shock events occurring in the same call centres suggest that hysteria may play a part. The condition is usually only seen when work-related issues are apparent.
The air conduction thresholds in the right and left ears, and the interaural asymmetry of thresholds at 0.5, 1, 2, 3, 4 and 6 kHz were measured in a group of 225 soldiers exposed to a variety of weapon noise who were referred for assessment because of a deterioration in hearing on routine testing. At 0.5 and I kHz the threshold levels rarely exceeded 25 dB and the interaural asymmetry was 10 dB or less in 90 per cent of cases. The degree of hearing loss and interaural asymmetry increased as the frequency increased, with the average loss being significantly greater in the left ear at 2, 3, 4 and 6 kHz.
Recommendations are made for the selection of cases of asymmetrical hearing loss exposed to weapon noise which require further investigation to exclude a retrocochlear cause or to define spurious hearing threshold levels.
Acoustic shock is a recently recognised clinical entity: following an abrupt, intense and unanticipated acoustic stimulus, usually delivered by a telephone handset or headset, some individuals report a symptom cluster that includes otalgia, altered hearing, aural fullness, imbalance, tinnitus, dislike or even fear of loud noises, and anxiety and/or depression. Symptoms start shortly after the triggering acoustic incident and can be short-lived or can last for a considerable time. If persistent, the condition can lead to significant disability. Proposed mechanisms include involvement of the tensor tympani muscle, hyperexcitability of central auditory pathways, and a precursive state of raised anxiety or arousal. A formal treatment programme has not yet been proposed, but the potential utility of modern therapeutic techniques for tinnitus and hyperacusis are considered. Given the large number of UK residents working in telephone call centres, this condition is of considerable clinical importance.
Three different types of noise-induced hearing loss have been reported in the literature. The two less common types are described here. Three cases of thesetwo types from our clinic are reported. Since these 2 types of noise-induced hearing loss often involve low frequencies it is important to recognize them in compensation cases.
Motorcyclists are known to be exposed to excessive wind noise levels when riding. The potential adverse effects of this exposure on their hearing was investigated. Temporary threshold shift (TTS) was assessed by asking 18 riders to undertake a standard test run of one hour at a steady 80 mph, and performing audiometry before and immediately afterwards. Permanent threshold shift (PTS) was assessed by performing pure-tone audiograms on a highly screened group of 246 motorcyclists and comparing their hearing thresholds with those of an appropriate control group obtained from the MRC National Study of Hearing.
Significant TTS was found at 0.25, 0.5,1 and 2 kHz. The greatest TTS occurred at 1 kHz, with a mean hearing loss of 10.3 dB. The hearing thresholds of the motorcyclists were significantly worse than the controls at 0.25, 0.5, 1 and 2 kHz, andwas most marked at 0.5 and 1 kHz where their hearing loss (PTS) was, respectively, 3.7 and 3.6 dB greater than expected.
These findings demonstrate evidence of both temporary and permanent hearing loss from motorcycling and present a strong argument for the need for some form of remedial action.
To measure the output sound pressure levels of personal music systems and evaluate their effect on hearing.
Output sound pressure levels at preferred volume settings and listening environment were measured using a manikin. Effects of personal music system use on hearing were evaluated using pure tone audiometry (in conventional and extended high frequency ranges), transient evoked otoacoustic emissions, syllable identification in noise, intensity discrimination, frequency discrimination and temporal modulation transfer function.
Results showed, alarmingly, that large proportions of young adults are using personal music systems at levels higher than the safety limits set by regulatory bodies. Individuals who listened to personal music systems at levels higher than 80 dB LAeq exhibited poorer extended high frequency thresholds, reduced transient evoked otoacoustic emission amplitudes, poorer frequency discrimination, reduced modulation detection thresholds at 32 Hz modulation frequency, and reduced syllable identification in noise at −5 dB signal-to-noise ratio. Listening levels were significantly correlated with extended high frequency thresholds and transient evoked otoacoustic emission amplitudes.
These results suggest that listening to music through personal music systems at higher volume levels may be hazardous to hearing.