Typical STC range and STC required in sleeping units are given as which of the following?

• A. 25-55 and 48
• B. 40-70 and 60
• C. 15-40 and 45
• D. 30-60 and 50

Answer: (D)

The idea being tested is how sound is blocked by interior partitions and what level of isolation is considered acceptable for sleeping spaces. STC, or Sound Transmission Class, measures how well a wall or partition reduces airborne noise; higher numbers mean better sound blocking. For sleeping units, the goal is to keep noise from adjacent spaces from being easily heard, so a minimum of about 50 is typically required to ensure privacy and comfort.

Interior walls can vary widely in performance depending on construction, with lighter partitions sometimes in the low 30s and heavier, well‑built assemblies reaching 50–60 or more. Saying the typical range is 30–60 acknowledges this variation while highlighting that 50 is the standard target for sleeping areas.

Other options imply a lower required STC or a range that doesn’t reflect common construction realities. A required 50, paired with a plausible 30–60 range, best matches standard practice for sleeping units.