Modelling the Subjective Road Traffic Noise Annoyance Levels in Nairobi City, Kenya

This study aimed to survey and evaluate the subjective noise annoyance levels in Nairobi City. Being the capital city of Kenya in East Africa, Nairobi is undergoing rapid growth, like many developing cities globally. Road traffic levels are witnessing a phenomenal increase, accompanied by a corresponding change in the ambient soundscape across the city. Previous research has shown that Road Traffic Noise (RTN) is the most prevalent pollutant that disturbs the quality of life in urban environments, hence the justification of the present research. The research team deployed customized questionnaires, which were distributed among samples across 42 locations. The questionnaires had two scales, the 0 - 10 Richter Scale and a 5-point verbal qualifying scale. A total of 384 participants were sampled from the main population frame, and each location had at least 9 survey questionnaires for each set. The Department of Civil and Construction Engineering, University of Nairobi, coordinated data collection across the city between 6^th July 2025 and 12^th July 2025. The data clerks conducted a purposive sampling for a face-to-face interview using the two scales. The two scales were combined, and on analysis, the level of highly annoyed (HA) individuals ranged between 10% and 100%. Further using OriginPro 2025b Software and MS Excel, different exposure-response relationships were developed to show how the equivalent sound pressure level varied with the number of highly annoyed individuals. It was found that, as the equivalent sound pressure level increased, so did the number of highly annoyed individuals. The low coefficient of determination (R²) values obtained compared well with those of other similar previous studies, which indicates that Nairobi has a high RTN environment. Further, the residents have adapted to chronic RTN exposure, which has lowered their perceptual sense of elevated sound pressure levels on the reported annoyance. Therefore, this study does provide a baseline for city authorities to develop and implement RTN’s abatement measures and policies aimed at making neighborhoods quieter. In addition, the new policy may transcend sustainable traffic flow management.