Which surfaces are covered by sound reducing surfaces?

• A. Floors
• B. Doors and windows
• C. Only ceilings in open offices
• D. Ceilings & Walls (and office cubicle partitions, if present); Ceilings: Open offices min NRC 0.9; Conference/Teleconference: min 0.8 on min 50% ceiling; Walls: Open offices min NRC 0.8 on min 25% walls; Enclosed offices/Conference/Teleconf min 0.8 on min 25%; Cubicle partitions min NRC 0.8 & 1.2m high

Answer: (D)

In acoustics for WELL, sound reduction comes from absorbing surfaces placed on key boundaries of a space, quantified by NRC, and specified for different space types. The requirement spans ceilings, walls, and, where partitions exist, cubicle partitions, with particular NRC values and coverage.

This option is the best because it explicitly includes ceilings and walls and also accounts for cubicle partitions when present, with the appropriate NRC targets and coverage: open offices require a high ceiling absorption (NRC around 0.9), conference/teleconference rooms specify ceiling absorption at 0.8 with at least half the ceiling covered, open offices require wall absorption of 0.8 on at least 25% of wall area, enclosed offices or conference/teleconference spaces require walls with 0.8 on at least 25%, and cubicle partitions must meet NRC 0.8 and be 1.2 meters high. Floors and doors/windows are not framed as the primary sound-absorbing surfaces in these criteria, so including only ceilings or excluding walls/partitions would miss key components of the standard.