Tinnitus and Other Auditory Problems – Occupational Noise Exposure below Risk Limits May Cause Inner Ear Dysfunction

Abstract

The aim of the investigation was to study if dysfunctions associated to the cochlea or its regulatory system can be found, and possibly explain hearing problems in subjects with normal or near-normal audiograms. The design was a prospective study of subjects recruited from the general population. The included subjects were persons with auditory problems who had normal, or near-normal, pure tone hearing thresholds, who could be included in one of three subgroups: teachers, Education; people working with music, Music; and people with moderate or negligible noise exposure, Other. A fourth group included people with poorer pure tone hearing thresholds and a history of severe occupational noise, Industry. Ntotal = 193. The following hearing tests were used:− pure tone audiometry with Békésy technique,− transient evoked otoacoustic emissions and distortion product otoacoustic emissions, without and with contralateral noise;− psychoacoustical modulation transfer function,− forward masking,− speech recognition in noise,− tinnitus matching.A questionnaire about occupations, noise exposure, stress/anxiety, muscular problems, medication, and heredity, was addressed to the participants. Forward masking results were significantly worse for Education and Industry than for the other groups, possibly associated to the inner hair cell area. Forward masking results were significantly correlated to louder matched tinnitus. For many subjects speech recognition in noise, left ear, did not increase in a normal way when the listening level was increased. Subjects hypersensitive to loud sound had significantly better speech recognition in noise at the lower test level than subjects not hypersensitive. Self-reported stress/anxiety was similar for all groups. In conclusion, hearing dysfunctions were found in subjects with tinnitus and other auditory problems, combined with normal or near-normal pure tone thresholds. The teachers, mostly regarded as a group exposed to noise below risk levels, had dysfunctions almost identical to those of the more exposed Industry group.

Self-Reported Hearing Loss and Pure Tone Audiometry for Screening in Primary Health Care Clinics

“… 27 Apart from different perceptions of hearing loss related to age, stress, anxiety, the presence of middle ear infection and tinnitus can also influence accurate self-report measures resulting in over- or underestimation of hearing loss. 28 - 30 As such, using self-report measures may not be sufficiently sensitive to identify hearing loss and may require a combined approach that includes a test in combination with self-report or as a second-stage screen. 21 …”

Tinnitus Severity Is Related to the Sound Exposure of Symphony Orchestra Musicians Independently of Hearing Impairment

“…Most of the subjects in the study by Guest et al (2017) had constant tinnitus but with a normal audiogram, whereas only a minority experienced constant tinnitus in the study by Moore et al (2017) (Guest et al, 2017; Moore et al, 2017). Tinnitus may be a preliminary indicator of hearing loss, and there is some evidence that tinnitus may be noise induced even in the presence of normal hearing thresholds (Guest et al, 2017; Hickox & Liberman, 2014; Lindblad et al, 2014; Schaette & McAlpine, 2011).…”

The post- noise exposed condition of the normal hearing workers with tinnitus and hyperacusis developed by the chronic occupational noise exposure

“…The consequent chronic noise exposure in occupational noise environment physically damage to the hearing of workers and critically affects their susceptibility in the noiseinduced stress and their quality of life 18,19 . The audiometry results, especially in the industry and education, were revealed that the workers who suffered from inner ear disorders were significantly higher than other occupational groups 16 .…”

“…The experimental subject with tinnitus has been working at a noisy construction site with an extremely loud booming sound that could cause hearing loss in healthy people, such as a metal banging sound or sound from heavy equipment. Even if his bilateral hearing thresholds were within normal range, see Table 1, tinnitus was developed because of chronic exposure to an extremely noisy working environment during working hours for a long duration 16,43 .…”

“…Regarding occupational noise environments, there have recently been studied with a large number of subjects, of hundreds to thousands, regarding clinical effects of the occupational noise exposure, e.g., construction [12][13][14] , industry 15 , comparisons of the four occupations (cf. education, music, industry and other occupational noise environment 16 , and obstetric wards 17 . In usual circumstances of these working environments, occupational noise is a usual condition of long-term and higher than 80dB of noise exposure, continuously generated from the working environments in every day and whole time of the working hours 12 .…”