A study among the population of Bangkok indicated that drivers and street vendors are particularly at risk for hearing loss due to their daily work in the noisiest neighbourhoods. In all, 4,000 people had their hearing tested, and noise levels were recorded in central areas.
Workers in the inner city of Bangkok were found to be the group most exposed to daytime noise levels of 83 dB. Drivers working in the area were most affected by the constant noise. Inner-city drivers had an average hearing threshold between 37 dB and 58 dB, depending on their age.
In comparison, the hearing threshold of drivers in less noisy areas ranged between 13 and 44 dB. The hearing threshold is the minimum sound level required for hearing a sound. The higher the hearing threshold, the worse the hearing.
Street vendors were similarly affected with average hearing thresholds between 37 and 56 dB. Average hearing thresholds among street vendors in other areas were recorded at between 10 and 34 dB.
The long hours in the noise is the reason for the increased risk of hearing loss to the drivers and street vendors.
Traffic officers and people living in the inner core were also found to have worse than average hearing, but according to the study traffic noise was not the cause. Their direct exposure to road noise is of shorter duration.
Unfit for human habitation
However, three of the four districts examined were found to be unfit for human habitation. Daytime noise levels in these districts were recorded at between 76 and 83 dB. Nighttime noise levels were between 60 and 75 dB.
According to Thai authorities, average noise levels in residential areas with round the clock noise exposure should not exceed 70 dB.
Source: Monitoring and Assessment of Daily Exposure for Roadside Workers to Traffic Levels in an Asian City: A Case Study of Bangkok Streets, Environmental Monitoring and Assessment, 2003.