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Work idoneity in hearing loss must be related to working ability and evolution risks. Working ability is referred to the difficulties found in speech comprehension and in signals perception. As regards hearing loss evolution it is necessary to define if the subject is affected by conductive or neurosensorial hearing loss. In conductive hearing loss it is necessary to evaluate entity and frequential distribution of the deficit. In neurosensorial hearing loss it is necessary to distinguish between noise-induced hearing loss and extraprofessional hearing loss. In noise-induced hearing loss the evolution risk is high if the noise exposure is less than 10-15 years or the actual noise exposure is louder than the former. In case of extraprofessional hearing loss the evolution risk is higher in presbycusis, endolymphatic hydrops and toxic hearing loss. The necessity to report the presence on professionale noise-induced hearing loss arises if audiometric threshold is more than 25 dB at 0.5-1-2-3-4 kHz and if it is verified the professional origine of hearing loss.

The aims of this study were to evaluate the influence of age and exposure to noise in determining the evolution of hearing loss after noise-induced hearing loss has been already established and to define the further evolution of presbycusis. This is a cross-sectional study based on the evaluation of pure-tone audiometry threshold on 568 subjects affected by noise-induced hearing loss and exposed to noise for at least 10 years; noise exposure at testing was 85-90 dB Leqd(A). The further evolution of hearing loss was found to be more related to age than to noise exposure and was significantly less than expected for presbycusis. In conclusion our data support the hypothesis that once NIHL has manifested, it tends to worsen slightly with continued noise exposure and that progressive hearing loss is chiefly due to aging. However, in individuals with NIHL, age-related hearing loss is significantly less at frequencies damaged by noise than in non-noise-exposed individuals.

Subjective disturbances, due to hearing loss, are auditory disability and handicap which can be evaluated with a questionnaire. The present study refers to a population of industrial workers affected by noise-induced hearing loss. Aim of the study is to identify the minimal level of hearing loss over which the patient felt changes in his quality of life, and the average auditory threshold at which the patient considered the application of a hearing aid useful or necessary. The sample comprised 180 males with noise-induced hearing loss. Each subject received a questionnaire designed for this study. Data show a correlation between disability, handicap and the degree of noise-induced hearing loss. The most relevant problems in noise-induced hearing loss are correlated with disability rather than handicap. 35 dB can be considered as the level above which these devices can be suggested to patients. Hearing aids can become a therapeutic instrument even in the presence of a low degree of hearing loss.

Background: The term auditory disability (AD) means the presence of auditory symptoms due to hearing loss. Until now the audiometric threshold cut-off between the presence or absence of AD was not clear., Objectives: In this study we attempted to define the value of audiometric threshold that could be considered as the limit between the presence or absence of weakness of auditory function, considered as the threshold as the 95th percentile of subjects that did not report AD., Methods: The study group consisted of 1641 males, 891 normally hearing and 750 affected by noise-induced hearing loss (NIHL) Each subject was submitted to a questionnaire specifically created in order to determine the presence of AD., Results: Statistical analysis confirmed the reliability of answers to items. AD was present in 577 subjects, not all affected by NIHL. Audiometric threshold and age correlated significatively with the degree of AD., Conclusions: The results obtained allowed the audiometric threshold values to be determined at the 95th percentile of subjects who did not report AD, in relation to the average of frequencies normally used in hearing loss evaluation.

Until now the relationship between auditory threshold and age has been evaluated in normal subjects only. In this study the Author reports results obtained in a cross-sectional study on 416 subjects suffering from noise-induced hearing loss who were exposed to noise for 10 years at least. The results show that hearing loss over time was more correlated to age than to noise exposure. Moreover, the evolution of hearing loss over time had a linear shape while in noise-induced hearing loss evolution has a logarithmic shape and in presbyacusis it has an exponential shape. The differential threshold between 30 and 60 years obtained by applying the linear regression model was, at higher frequencies, significantly reduced compared to normal subjects. These results suggest that threshold values related to age obtained in normal subjects can not be applied in subjects affected by noise-induced hearing loss.

The paper analyzes the 8 KHz threshold in subjects with noise-induced hearing loss. The study group consisted of 315 subjects occupationally exposed to noise and suffering from acoustic trauma, which was considered as a mean threshold of more than 25 dB at 2, 3 and 4 KHz. The mean shape of audiograms was characterized by a neurosensory deficit which was more elevated at 4 and 6 KHz whereas the threshold at 8 KHz was better. However, this pattern was found in 60% of the cases whereas in the remaining 40% the threshold at 8 KHz was worse. Subjects with the most impaired audiometric threshold at 8 KHz were mainly older, although cases were found in a low percentage of younger subjects. The results demonstrate that in individual cases it is impossible, on the basis of the shape of the audiogram, to establish whether a hearing loss is due to noise or age.

The aim of this study was to determine the relationship existing between auditory disability, according to WHO 1980, and pure tone audiometry threshold in noise induced hearing loss. Disability was evaluated on the basis of a questionnaire submitted to 286 subjects with acoustic trauma. Answers obtained were considered reliable on the basis of statistical analysis. Results showed that subjects with disability have an higher pure tone threshold than subjects without auditory disability. However it appears difficult to determine a precise threshold level ever which auditory disability may be considered present. The Authors suggest that this limit could be determined on the basis of pure tone threshold at the 10th centile of the group of subjects with disability or at the 90th centile of subjects without disability.

The paper examines the different aspects of the diagnosis of noise induced hearing disability and handicap. In the author's opinion a diagnosis of this kind can be made only if both an occupational acoustic trauma and a hearing disability or handicap are present. An occupational acoustic trauma can be considered to be present if the subject works in a noisy environment, if there are no auditory diseases other than of occupational origin, and if the audiometric threshold is neurosensorial, bilateral, more elevated at the higher frequencies and higher than the threshold of subjects on the same age but not exposed to industrial noise. On the other hand, the authors deem that there is a loss of hearing function when hearing disability and handicap are present according to the WHO definition. An experimental model is proposed that will establish the presence of hearing disability and handicap.