A noise reduction of ____ to ___ dBA is the goal of noise insulation projects.

• A. 10 to 15
• B. 20 to 30
• C. 30 to 35
• D. 40 to 50

Answer: (C)

Noise reduction targets for insulation are expressed in A-weighted decibels (dBA), which reflect how people actually perceive sound. For typical noise insulation projects, a reduction of about 30 to 35 dBA is a practical goal because it provides a noticeable improvement in indoor quiet without requiring extreme, costly construction. Smaller targets like 10–15 dBA or 20–30 dBA may fall short of comfort or regulatory needs, while aiming for 40–50 dBA would entail much heavier, costlier measures than usually necessary. In practice, if outside noise is around 70 dBA, a 30–35 dBA reduction would bring indoor levels to roughly 35–40 dBA, a comfortable range for most spaces.