A-weighted sound is the most typically used sound metric. This weighting system emphasizes the sound frequency ranges the ears are most sensitive to. In the map presented here, the lighter areas correspond to quieter areas while the darker levels correspond to louder areas.
In context, existing epidemiological studies suggest that negative health impacts resulting from noise exposure can occur at levels as low as 40 dBA (mood and sleep interference) with the most deleterious health effects occurring with exposures starting at 65 dBA (cardiovascular disorders such as hypertension). Further, according to the World Health Organization, recommended daytime sound levels should not exceed 55 dBA. In areas near schools, for example, should be no higher than 35 decibels. Anecdotally, we have never measured decibel levels lower than 35 dBA. We see here that there are several areas within the city that are well above levels shown to cause harm—especially those living near very busy roads.