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Auditory Fatigue Among Call Dispatchers Working with Headsets

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Auditory Fatigue Among Call Dispatchers Working with Headsets ORIGINAL PAPER International Journal of Occupational Medicine and Environmental Health 2018;31(2):217 – 226 https://doi.org/10.13075/ijomeh.1896.01131 AUDITORY FATIGUE AMONG CALL DISPATCHERS WORKING WITH HEADSETS THOMAS VENET1, AYOUB BEY2, PIERRE CAMPO1, JOËL DUCOURNEAU3, QUENTIN MIFSUD3, CHARLES HOFFMANN2, AURÉLIE THOMAS1, MARC MOUZÉ-AMADY4, and CÉCILE PARIETTI-WINKLER2,5 1 National Research and Safety Institute for the Prevention of Occupational Accidents and Diseases (INRS), Vandoeuvre, France Ototoxicity and Neurotoxicity Laboratory 2 Central Hospital, Nancy, France 3 Lorraine University, Nancy, France Hearing Aid Unit, Faculty of Pharmacy 4 National Research and Safety Institute for the Prevention of Occupational Accidents and Diseases (INRS), Vandoeuvre, France Physiology, Movement and Work Laboratory 5 Lorraine University, Nancy, France DevAH – EA 3450 Laboratory Abstract Objectives: To determine whether call center dispatchers wearing headsets are subject to auditory fatigue at the end of a work shift. Material and Methods: Data was gathered at times when call centers were busiest. All call operators wore a headset for up to 12 h. Acoustic environment and noise exposure under the headset were continuously recorded during the entire work shift. Variations in auditory parameters were assessed using pure-tone air-conduction audiometry and an objective test based on distortion product otoacoustic emissions – contralateral suppression of distortion product otoacous- tic emission (DPOAE) amplitudes (EchoScan test). Thirty-nine operators and 16 controls, all volunteers, were selected from 3 call centers (sales, assistance, and emergency) where all cognitive tasks were accomplished by phone and on comput- ers. Results: No acoustic shock was detected during the investigation. The highest normalized noise exposure (daily noise exposure level – LEX,8 h) measured was 75.5 dBA. No significant variation in auditory performances was detected with either pure-tone air-conduction audiometry or the EchoScan test. Nevertheless, dispatchers expressed a feeling of tiredness. Conclusions: For an equivalent diffuse field noise exposure, the use of a headset does not seem to worsen auditory fatigue for call center operators. The dispatcher’s fatigue was probably due to the duration of the work shift or to the tasks they performed rather than to the noise exposure under a headset. Int J Occup Med Environ Health 2018;31(2):217 – 226 Key words: Risk assessment, Noise, Auditory fatigue, Headset, Call center, EchoScan Funding: this research was fully funded by National Research and Safety Institute for the Prevention of Occupational Accidents and Diseases (INRS, France) and by Nancy Central Hospital. Received: September 19, 2016. Accepted: January 11, 2017. Corresponding author: T. Venet, National Research and Safety Institute for the Prevention of Occupational Accidents and Diseases (INRS), Ototoxicity and Neurotoxicity Laboratory, Morvan St, CS 60027, 54519 Vandoeuvre, France (e-mail: [email protected]). Nofer Institute of Occupational Medicine, Łódź, Poland 217 ORIGINAL PAPER T. VENET ET AL. INTRODUCTION Occupational hearing loss is defined as a hearing deficit In France, occupational physicians have expressed major caused by work-related irreversible cochlear dysfunction concerns about call operators’ hearing acuity. Part of this con- whereas auditory fatigue is a more subtle concept. First of cern is due to reports that considerable acoustic levels may all, auditory fatigue must be temporary, that is a required be recorded under headsets [1]. Acoustic shocks received condition. Auditory fatigue is due to 2 main phenomena through headsets could, naturally, be a source of cochlear located at the level of the peripheral receptor. Liberman trauma [2,3]. In addition, Trompette and Chatillon [1] and Dodds [7] showed that the rootlets of the stereocil- found that up to 12% of equivalent diffuse field levels ex- ia are shortened after moderate-noise exposures, given ceeded 80 dBA, with maximum levels of up to 90 dBA. more flexibility to the structures. Moreover, we all know Most operators in traditional and emergency call centers the swellings underneath the inner hair cells because of work with a headset in open spaces. These conditions a massive release of glutamate within the synaptic cleft. mean that operators are exposed to environmental noise Both mechanisms contribute to the establishment of a pe- in addition to the communications received through their ripheral auditory fatigue. headsets. The ambient noise on the platform is naturally For this study, ambient noise and the noise at workstations of a much lower intensity than the noise emitted through were recorded throughout the work shift, and operators’ the headset, and could be even negligible in terms of hearing was verified using 2 different approaches. Subjec- overall noise exposure. However, the ambient noise may tive audiometric thresholds were determined by pure-tone affect the intelligibility of incoming messages, causing air-conduction audiometry (PTA), which is the current operators to adjust the volume settings on their headset internationally-recognized reference screening tool to as- in an attempt to improve the signal-to-noise ratio. The sess NIHL. This technique relies on individuals’ ability to greater the ambient noise, the more the operator should determine thresholds of hearing sensations related to fre- increase the volume on the headset [1,4]. Therefore, the quency-specific acoustic stimuli. Thus, in PTA, the central ambient noise may indirectly modify the overall noise auditory system analyzes each piece of information coming exposure. from the peripheral auditory receptor, and could correct Noise-induced hearing loss (NIHL) is associated with for subtle ear dysfunctions or metabolic fatigue to ensure a number of risk factors related to the intensity and du- the highest possible level of performance [8–10]. Due to ration of noise exposure. The Occupational Safety and these retro-cochlear compensatory mechanisms, PTA re- Health Administration (OSHA) in the United States [5], sults may underestimate NIHL. and European legislation [6] require workers whose 8-h For this reason, we also used an objective test for mea- average daily exposure exceeds 85 dBA and 80 dBA, re- suring auditory fatigue. In this test, acoustic stimulation spectively, to be enrolled in a hearing conservation pro- of the efferent reflexes (ER) is used alongside measure- gram. However, in the context studied here, although ment of the distortion product otoacoustic emissions. The exposure may last for a long period, operators are rarely recently developed EchoScan [11] device was chosen as exposed to high noise levels, apart from cases of acoustic appropriate for these types of measurement. As EchoScan shock. It is important to keep in mind that the purpose of elicits the trigger of the efferent reflex, which is defined this study has not been to investigate the effect of acoustic as the sum of the effects provoked by the stapedial and shocks, but rather to assess potential auditory fatigue due olivo-cochlear reflexes, the data obtained is not influenced to the long duration of exposure. by retro-cochlear compensatory mechanisms, thus mak- 218 IJOMEH 2018;31(2) CALL DISPATCHERS’S AUDITORY FATIGUE ORIGINAL PAPER ing the test more objective and sensitive than PTA. In- administrative or management tasks. The average age of deed, the threshold of the ER trigger is very sensitive to the operators was 35.5 years old whereas it was 41.5 for auditory fatigue due to noise [11]. the controls. Call center operators often complain about auditory fa- tigue at the end of their work shift, and that was the case Control noise exposure too during this study, but the factors contributing to this fa- The volunteers were fitted with noise dosimeters (ACOEM tigue have yet to be objectively studied. So, it was relevant WED) conforming to the American National Standards to evaluate the auditory fatigue suffered by the operators Institute (ANSI S1.25) [12] and to the International Elec- at the end of their work shift. The main goal of this pilot trotechnical Commission (IEC 61252) [13]. They wore the study was to determine whether call dispatchers present dosimeter throughout their working day on the shoulder, evidence of peripheral (EchoScan) and/or central auditory and the data it recorded was used for determining the fatigue (PTA) at the end of a work shift. noise exposure level to which each individual was exposed to during their work shift. Dosimeters were controlled MATERIAL AND METHODS with the following parameters: 94 dB at 1000 Hz before Cohort starting the measurements. The cohort for this study consisted of 55 operators be- A 1-second time integration was used for recording tween the age of 19 and 56 years old. Subjects were re- the A-weighted equivalent sound level (LAeq), C-weighted cruited from hotline call handlers at a French telecom equivalent sound level (LCeq) and C-weighted peak sound provider (N = 37), the emergency medical call center at pressure level (Lp,Cpeak). The daily noise exposure for a hospital (N = 14), and a technical hotline center (N = 4). the 8-h reference period was calculated with a 3 dB ex- The study protocol was approved by the national eth- change rate: ics committee (CPP 2014-A01904-43, authorization code PSS-2014/ECHOSAM-PARIETTI/MS). All volun- 10×log(t/8) (1) teers gave written consents for participation in this study prior to determining their eligibility. where: Medical
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