The role of audiometry in the prevention of occupational deafness

The research set out to test three main hypotheses derived from a summary of literature relevant to the use of audiometry in industry. These hypotheses were: (1) performing audiometry increases the probability that hearing protectors, once issued, will be worn; (2) audiometry is considered by workers to be evidence of their employer's concern for their welfare; (3) audiometry is associated with common law claims by workers against employers for alleged occupational deafness. Six subsidiary hypotheses were also developed. Four methods of data collection were used: (1) attitude questionnaires were administered to samples of workers drawn from an industrial company performing audiometry and two industrial companies not performing audiometry; (2) a postal questionnaire was sent out to industrial medical officers; (3) surveys were undertaken to assess the proportion of the workforce in each of eight industrial companies that was wearing personal hearing protectors that had been provided; (4) structured interviews were carried out with relevant management level personnel in each of five industrial companies. Factor analysis was the main statistical analytic technique used. The data supported all three main hypotheses. Audiometry was also examined as an example of medical screening procedure. It was argued that the validation of medical screening procedures requires the satisfaction of attitudinal or motivational validation criteria in addition to the biological and economic criteria currently used. It was concluded that industrial audiometry failed to satisfy such attitudinal or motivational criteria and so should not be part of a programme of screening for occupational deafness. It was also concluded that industrial audiometry may be useful in creating awareness, amongst workers, of occupational deafness. It was argued that the only profitable approach to investigating the role of audiometry in preventing occupational deafness is to study the attitudes and perceptions of everyone involved.

Hearing protectors: a dilemma involving acoustics and personal safety

This thesis is concerned with the optimising of hearing protector selection. A computer model was used to estimate the reduction in noise exposure and risk of occupational deafness provided by the wearing of hearing protectors in industrial noise spectra. The model was used to show that low attenuation hearing protectors con provide greater protection than high attenuation protectors if the high attenuation protectors ore not worn for the total duration of noise exposure; or not used by a small proportion of the population. The model was also used to show that high attenuation protectors will not necessarily provide significantly greater reduction in risk than low attenuation protectors if the population has been exposed to the noise for many years prior to the provision of hearing protectors. The effects of earplugs and earmuffs on the localisation of sounds were studied to determine whether high attenuation earmuffs are likely to have greater potential than the lower attenuation earplugs for affecting personal safety. Laboratory studies and experiments at a foundry with normal-hearing office employees and noise-exposed foundrymen who had some experience of wearing hearing protectors showed that although earplugs reduced the ability of the wearer to determine the direction of warning sounds, earmuffs produced more total angular error and more confusions between left and right. !t is concluded from the research findings that the key to the selection of hearing protectors is to be found in the provision of hearing protectors that can be worn for a very high percentage of the exposure time by a high percentage of the exposed population with the minimum effect on the personal safety of the wearers - the attenuation provided by the protection should be adequate but not a maximum value.

Mechatronic solutions for measuring disturbance levels within a cochlea

Hearing implants are an important devices for combating deafness over the next 15 years. In this paper, we focus on the means to determine the sensitivity of the hearing organ to disturbances produced by implants and other interventions, and those induced by implantation. The preservation of residual hearing is an important aspect to be considered, however, the sensitivity of this to the process of implantation, device location and power levels is not well understood. Within this paper, a new experimental set-up to contrast the merits of different implantation techniques, implant location and power transmission are discussed and the initial results regarding disturbance levels using different surgical techniques are described.