MAXIMUM CONCENTRATION LIMITS ARE AVAILABLE FOR AIR POLLUTANTS Fig. 2.4. Recommended Maximum Launch-Related Air Pollutant Concentrations Launch and Recovery Noise. Noise impacts from SPS operations will come from the sound level generated by the heavy lift launch vehicle (HLLV) during ascent and from sonic booms created during ascent and reentry. Figure 2.6 shows the sound pressure levels of the HLLV. To assess the impacts of these levels on the public, two conversion steps are necessary. First, the absolute sound pressure must be converted to what is called an A-weighted level to account for the sensitivity of the human ear to different frequencies. Second, the short-term sound pressure levels must be integrated into an overall sound level using weighting factors that account for time of day, frequency of occurrence, and duration of noise level. The U.S. Environmental Protection Agency uses a 24-hour weighted average for its 70 db(A) daytime guideline and its 50 dB(A) nighttime guideline. Considering that the overall
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