There are two maps – one for the unmitigated sound levels from plant operations and another resulting from the “presumed” impact of mitigation. This latter point is important. They do not know the final design of the plant and they have made assumptions about sound transmission from the plant and the mitigation they think they can provide. In their own words, the design is “conceptual.”
The “conceptual” design and mitigation factors result in a noise map that essentially comes in just under the limits permitted. The mitigated noise map clearly indicates that this is based on “conceptualized” mitigation measures.
The unmitigated map indicates there will be 65-75 dBA (decibels) of noise and disturbance within the light mint area on the map. Imagine a constant buzz and drone. A dog barking or an alarm clock is 70 dBA.
This noise measurements are based on what the power plant will produce. It does not include freeway or ambient noise from other sources. You need to add these other noises for an accumulative effect.