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.