Sound-attenuation improvements and sound insulation of homes are intended to reduce interior residential noise levels to at least ______ dBA within the ______ contour.

• A. 50 dBA within the 65 dBA contour
• B. 45 dBA within the 60 dBA contour
• C. 55 dBA within the 70 dBA contour
• D. 60 dBA within the 65 dBA contour

Answer: (A)

The idea is that exterior noise is reduced by building insulation to keep interior living spaces quiet enough for comfort. The 65 dBA contour is a standard boundary used in planning to denote where aircraft or similar noise is significant. Within that area, the goal is to achieve an interior noise level of about 50 dBA, which is a practical target that can be reached with typical improvements to windows, walls, seals, and ventilation. This pairing (50 dBA inside, within the 65 dBA contour) aligns with common practice for making homes livable in noisier zones.