Noise is any sound that causes physiological uneasiness to the ear. People in many environments today, especially urban ones, are exposed to such noise without realizing its potential danger to their healthy hearing. This situation is largely contributed to by the little attention that most governments, especially in the developing countries, pay to noise as a pollution issue. This paper describes a study that aimed at measuring the noise levels at selected points in Nairobi's CBD with a view to generate a noise map over the study area in addition to identifying areas of high noise intensity or noise hot spots. The study found that noise levels, on average, varied from 61 db to 78 db, increasing from the west to the east of the CBD, and emanated mainly from vehicular traffic; several noise hotspots were also identified, and they are located mainly to the east of the CBD. The paper concludes that although the study was not city-wide, the noise levels observed are high enough to warrant further research and action by the environmental authorities.