ADVANCEMENT OF THE SCIENCE
Morning Hours Noise Level Map for Study Locations FIGURE 2
sampling point. Prior to data collection, the sound level meter was calibrated using estab- lished protocols (Paiva et al., 2019). Sampling Design and Procedure Two daily peak times, morning (7 a.m. to 10 a.m.) and evening (5 p.m. to 7 p.m.), which correspond with times of increased commer- cial and traffic activity, were used to record noise data at each of the 20 locations. To rep- resent the typical human ear location, mea- surements were made at a height of approxi- mately 1.5 m above ground (ISO, 2017). At each sampling site, A-weighted equiva- lent continuous sound levels (Leq) were monitored at 5-min intervals over a 30-min sample period (6 readings per session) each
morning and evening. The noise exposure at that location and time was represented by averaging these values. To guarantee mea- surement validity and consistency, environ- mental factors such as wind, rain, and abrupt disruptions were recorded (World Health Organization [WHO], 2018). Spatial Analysis and Noise Mapping GIS software (ArcGIS 10.8) was used to pro- cess and analyze the GPS coordinates and associated noise level data. The inverse dis- tance weighting (IDW) technique, which cal- culates noise intensity values for unsampled points based on closeness to sampled points, was used to do spatial interpolation (Oyedepo & Saadu, 2009). This method made it easier
to create noise contour maps for Lagos that differentiated between exposures in the morning and evening. Health Risk Assessment Reports from the Occupational Safety and Health Administration (OSHA), American Conference of Governmental Industrial Hygienists (ACGIH), and WHO, along with previous research on noise-induced hear- ing loss in Nigerian workers (Ogungbe & Amosu, 2017; Shehu et al., 2020) were used to evaluate the health risks associated with increased noise exposure. To infer potential dangers to itinerant workers, self-reported adverse effects (e.g., hearing problems, sleep disturbance, stress, irritability) noted in
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Volume 89 • Number 4
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