Dear Editors,
It was a pleasure for us to read the article titled ‘Comparison of distortion product otoacoustic emissions and pure tone audiometry in occupational screening for auditory deficit due to noise exposure’ by Wooles et al.,Reference Wooles, Mulheran, Bray, Brewster and Banerjee 1 in your esteemed journal. It is a succinctly written article and we would like to commend the authors on their excellent effort. The topic is significant to us, as we have been conducting a similar study in our institution for the past three years, involving factory workers. Based on our experience in this area, we would like to mention a few points that we feel would enrich the above article.
Exposure to short duration, high-level noise can cause either temporary or permanent hearing loss depending on the level, duration and spectral content of the traumatising stimulus. Various studies have validated the use of high-frequency pure tone audiometry in the detection of noise-induced hearing loss, and shown that extended high frequencies may be affected by noise sooner than is revealed by conventional audiometry.Reference Porto, Gahyva, Lauris and Lopes 2 We feel that high-frequency audiometry is an effective and cost-efficient screening tool for occupational hearing loss, and distortion product otoacoustic emissions testing may be considered if the high-frequency pure tone audiometry results warrant it.
Noise, as we know it, is excessive auditory stimulation. It elicits shear forces in the cochlea, leading to two pathways of cochlear injury, mechanical and metabolic. When the metabolic or mechanical stress is excessive, it leads to apoptosis or necrosis, and subsequent cell death.Reference Ylikoski, Xing-Qun, Virkkala, von Numers, Pirvola, Henderson, Prasher, Kopke, Salvi and Hamernik 3 Vibration-induced hearing loss, another oft neglected but frequently important factor under the umbrella of occupational hearing loss, acts via vibratory energy. This energy reaches the cochlea, and generates segmental compressions and expansions of the cochlear shell, affecting the fluid pathways of the inner ear.Reference Sohmer, Freman, Geal-Dor, Adelman and Savion 4 Although the iatrogenic role of vibration-induced hearing loss and the effect of vibration on the upper limbs have been studied in some detail, the role of occupational exposure to high-frequency vibration as a cause of hearing loss has not been fully explored, and we feel that this area warrants future research.
We found very few articles in the available literature regarding short-term exposure to noise as an occupational hazard for health professionals.Reference Dodenhoff 5 Specialists in otolaryngology, dental surgery and orthopaedic surgery are routinely exposed to short duration, high-frequency noises in the operating theatre. It would be worthwhile to study the long-term effects of this noise as an occupational hazard in these specialties; if warranted, protocols may be introduced to bring in measures for hearing protection in these specialties.
