Is the Level of Noise in a School Environment be Harmful to the Hearing of Teachers?

THIEME Original Research Is the Level of Noise in a School Environment be Harmful to the Hearing of Teachers? Gabriela Guenther Ribeiro Novanta1 Sergio Luiz Garavelli2 1 Department of Speech Language Pathology and Audiology, Centro Universitário Planalto do Distrito Federal (UNIPLAN), Brasília, DF, Brazil 2 Division of Engineering, Centro Universitário de Brasília (UNICEUB), Brasília, DF, Brazil 3 Laboratory of Otorhinolaringology Research, Universidade de Brasília, Brasília, DF, Brazil Andre Luiz Lopes Sampaio3 Address for correspondence Gabriela Guenther Ribeiro Novanta, Master, Departamento de Fonoaudiologia, Centro Universitário Planalto do Distrito Federal, Avenida Pau Brasil Lote 2, Brasília, DF, 71916-500, Brazil (e-mail: ). Int Arch Otorhinolaryngol 2020;24(4):e503–e507. Abstract Keywords ► noise ► faculty ► otoacoustic emissions ► spontaneous Introduction The excessive noise observed in the school environment can cause damages or losses to the learning process as well as risks to the health of teachers and students, such as physical, mental and social impairments, including, among them, hearing loss. Objective To assess otoacoustic emissions in teachers and determine whether classroom noise reduces distortion-product otoacoustic emissions (DPOAEs) amplitude and signal-to-noise ratio (SNR). Method Sixty-seven teachers were evaluated using otoacoustic emissions testing in two situations: after hearing rest and after the working day. Results Signal amplitude (p ¼ 0.044 [2 kHz]; p ¼ 0.01 [4 kHz]) and SNR for frequencies of 2 kHz (p ¼ 0.008) and 4 kHz (p ¼ 0.001) decreased significantly between time points. Mean classroom noise was associated with the magnitude of the difference in signal amplitude at 2 kHz (p ¼ 0.017) and 4 kHz (p ¼ 0.015), and SNR at 4 kHz (p ¼ 0.023). Conclusions There was a decrease in the amplitude and in the SNR after exposure to the noise in the classroom environment. The high levels of sound pressure that teachers are exposed to on a daily basis can cause a temporary change in the outer hair cells of the Corti organ, and these changes may become permanent over time. Introduction The excessive noise present in schools has been a complaint frequently reported by teachers in Brazil. The classroom, which is often built with inappropriate acoustic requirements or low noise isolation, suffers from both external and internal sources of noise.1–3 Factors such as background noise levels, the difference between speech signal and noise, and reverberation time directly influence communication inside the classroom.3,4 The American National Standards Institute (ANSI)5 recommends that noise in an unoccupied classroom should not received April 4, 2019 accepted December 21, 2019 DOI https://doi.org/ 10.1055/s-0040-1702969. ISSN 1809-9777. exceed 35 dB (A), and the difference between the voice of the teacher and the background noise should be more than 15 dB to the children’s ears. Although the Brazilian Association of Technical Norms (ABNT) has established that noise inside the classroom should not exceed 50 dB (A),6 several studies conducted in Brazil3,4,7,8 have reported intensities close to or higher than 60 dB (A). Excessive noise can disturb people at work, rest, and sleep, impair hearing, and other physical effects can include muscle tension and increased blood pressure (hypertension).8–12 With respect to teachers, the main complaints are related to fatigue, stress, headaches, and anxiety.1,2,8,13 Copyright © 2020 by Thieme Revinter Publicações Ltda, Rio de Janeiro, Brazil 503 504 The Level of Noise in a School Environment Novanta et al. Intense noise exposure may generate temporary or permanent hearing disorders. Temporary threshold shift occurs when the ear reduces auditory sensitivity for a short period of time but is able to recover fully upon cessation of exposure.12 The presence of these temporary changes may indicate a susceptibility to permanent hearing loss.12,14,15 When a permanent and gradual hearing reduction occurs due to exposure to high levels of sound pressure, the result is noiseinduced hearing loss (NIHL). Several studies have used distortion-product otoacoustic emissions (DPOAEs) as a means of assessing the functionality of outer hair cells in workers exposed to noise, as this test permits the identification of the beginning of cochlear injury, even before any change can be perceived via audiometry9,16,17. The advantage of using DPOAEs refers to the sensitivity in the early identification of changes caused by noise, due to their good record at the frequency of 4 KHz, frequency affected by NIHL.17 Therefore, DPOAEs can improve the efficacy of hearing preservation programs by providing more direct and reliable measurement of early changes and damage to the inner ear.17,18 Within this context, our objective was to assess DPOAEs in a group of teachers in the Federal District of Brazil to determine whether noise in the classroom would reduce the amplitude and signal-to-noise ratio (SNR) of DPOAEs. Methods This was a cross-sectional study involving primary school teachers from four schools that belong to the public school system of Samambaia in the administrative region of the Federal District. The schools were chosen at random by regional education coordinators at sites without marked exposure to sources of external noise, such as construction work, traffic, or industries. All teachers from the selected schools were invited to participate in the study. Due to the refusal of some professionals, the selected sample consisted of those who agreed to participate in the study. Sixty-seven out of 110 invited teachers were included in this study by self-agreement and fulfillment of the eligibility criteria. The exclusion criteria were the presence of earwax, use of a hearing aid, exposure to occupational noise outside the classroom, inflammatory and infectious diseases of the middle or external ear, and use of common ototoxic drugs (aminoglycoside antibiotics, salicylates, quinine, antineoplastic agents and loop diuretics). No participants were excluded. Procedure The study was conducted in two stages: before the beginning of classroom work (with a hearing rest) and at the end of classes (after the working day). All teachers evaluated had signed a contract to work 40 hours per week, with classroom exposure time corresponding to one shift (5 hours of exposure). The ear canal was initially inspected to determine the presence of ear wax, secretions, and perforation of the tympanic membrane. Teachers were then placed inside a Prostec portable sound proof booth for the examination of DPOAEs. The right ear of each individual was the first to be International Archives of Otorhinolaryngology Vol. 24 No. 4/2020 tested in all cases, followed by the left ear. The DPOAEs equipment used in the present study, Ero-Scan (MAICO Diagnostics, Eden Prairie, MN, USA), automatically monitored noise levels, the linearity of the stimulus during the (...truncated)