8.2 Sound Barriers (S03) & Minimum Background Sound (S06)

8.2 Sound Barriers (S03) & Minimum Background Sound (S06)

Core Exam Takeaway: S03 Sound Barriers (3 pt / WELL Core 3 pt) = Part 1 design values (STC, 1 pt) and Part 2 field-verified values (NIC, 2 pt). The two tables are identical in structure, with NIC values exactly 5 points below the corresponding STC values — 60/55/50/45/40 for STC and 55/50/45/40/35 for NIC. S06 Minimum Background Sound (2 pt / Core 4 pt) = sound masking at 48 dBA in open Quiet/Circulation areas and 42 dBA in enclosed Quiet rooms.

STC vs. NIC — the single most useful distinction in the concept

NIC is always lower than the STC of the wall in it, because real construction leaks: penetrations, back-to-back outlets, unsealed head-of-wall conditions, and above all flanking paths over ceilings, under raised floors and through shared ductwork. WELL's 5-point offset between its STC and NIC tables is a realistic allowance for exactly that gap — and it is why S03 pays twice as much for Part 2 as for Part 1.

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Feature S03: Sound Barriers — Optimization (3 pt / WELL Core 3 pt)

Intent: increase the level of sound isolation and speech privacy between enclosed spaces.

S03 Part 1 — Design for Sound Isolation at Walls and Doors (1 pt / Core 1 pt)

(a) Interior walls meet these minimum STC or R_w values. If an interior wall meets multiple categories, use the highest (most stringent) value listed.

(b) Doors that connect two occupiable rooms, and doors to mechanical equipment rooms, have:

• a non-hollow core,
• minimum STC/R_w of 30, and
• seals at the head, jamb and base.

WELL Core guidance: extent of developer buildout. Demising walls separating tenant spaces from common areas or other tenant spaces should use the "Loud zones and other occupiable spaces" category — i.e., STC 60.

S03 Part 2 — Achieve Sound Isolation at Walls (2 pt / Core 2 pt)

Option 1: Noise isolation class. For walls separating regularly occupied spaces, meet these minimum NIC or D_w values, again taking the highest where multiple categories apply:

Option 2: Speech privacy. For walls separating regularly occupied spaces, the sum of the measured NIC (or D_w) combined with the Noise Criteria rating (NC) or A-weighted sound pressure level (L_Aeq) within the receiving room achieves stated minimum composite values by source-and-receiver pairing — for example a minimum of 80 where the receiver room is any open area for concentration. Again, use the highest value where multiple categories apply.

[!IMPORTANT] Option 2 is conceptually the most sophisticated requirement in the Sound concept, and it rewards understanding rather than memorization. Speech privacy is not a property of a wall; it is the relationship between how much sound the wall stops and how much background sound exists in the room receiving it. A wall achieving NIC 35 in a room with NC 40 delivers a composite of 75; the same wall in a library-quiet NC 25 room delivers only 60. This is the mathematical reason S06 sound masking works — raising the receiver room's background level raises the composite without touching the wall.

[!TIP] The demising-wall rule for WELL Core is a genuine trap. A tenant demising wall is not obviously a "Loud zone" boundary, but WELL Core guidance directs projects to treat it under that category anyway — pushing the requirement to STC 60, the strictest value in the table.

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Feature S06: Minimum Background Sound — Optimization (2 pt / WELL Core 4 pt)

Intent: increase acoustical privacy within and between occupied spaces using dedicated artificial sound to uniformly raise speech privacy.

S06 Part 1 — Provide Minimum Background Sound (1 pt / Core 2 pt)

For office spaces.

• (a) A sound masking system is installed in open areas with Quiet zones, Circulation zones and enclosed rooms labeled as Quiet zones, producing a 1/3 octave band adjustable output signal and frequency spectrum of 100 Hz to 5 kHz.
• (b) The system is commissioned such that the following sound pressure levels are not exceeded:
  1. Open areas with Quiet zones and/or Circulation zones: 48 dBA
  2. Enclosed rooms labeled as Quiet zones: 42 dBA
• (c) The system is verified by a professional sound masking system installer in accordance with ASTM 1573-18 or an equivalent standard.

S06 Part 2 — Provide Enhanced Speech Reduction (1 pt / Core 2 pt)

For all spaces. The project achieves both:

• (a) Two points in either S03 Part 2 (Achieve Sound Isolation at Walls) or S05 Part 1 (Implement Sound Reducing Surfaces); and
• (b) S06 Part 1 (Provide Minimum Background Sound).

Note: documents submitted for S05 Part 1 during Precertification may be used to meet S06 Part 2 requirements. WELL Core guidance: Part 1 must be met in the whole building to earn the optimization; Part 2 in non-leased spaces with an additional point for leased spaces.

+-----------------------------------------------------------------------------+
|            WHY MASKING WORKS: SPEECH PRIVACY IS A RATIO                     |
|                                                                             |
|   Intelligibility depends on the SIGNAL-TO-NOISE ratio at the listener,     |
|   not on the absolute loudness of the talker.                              |
|                                                                             |
|   Overheard speech at 45 dBA in a room with 35 dBA background               |
|      -> +10 dB signal-to-noise -> clearly intelligible                      |
|                                                                             |
|   Same speech at 45 dBA in a room masked to 48 dBA                          |
|      -> -3 dB signal-to-noise -> unintelligible murmur                      |
|                                                                             |
|   Nothing about the talker or the wall changed. Only the FLOOR moved.       |
|                                                                             |
|   This is also why S06 CAPS the masking level: push past 48 dBA and the     |
|   masking itself becomes the annoyance, and S02's ambient limits fail.      |
+-----------------------------------------------------------------------------+

[!IMPORTANT] S02 and S06 must be read together. S02 caps average ambient sound at 45 dBA in Category 3 open areas for the 3-point tier, while S06 permits masking up to 48 dBA in open areas with Quiet or Circulation zones. Those are different measurements of different things — S02 measures unwanted noise from HVAC and exterior intrusion, S06 measures deliberately engineered masking sound — but a project pursuing both must design the total soundscape carefully rather than treating the features independently.

[!TIP] The 100 Hz to 5 kHz spectrum is not arbitrary: it is the band that carries the intelligibility-bearing content of human speech, particularly the consonant information between roughly 2 and 4 kHz. A masking system that produced only low-frequency rumble would be audible without masking anything, which is why WELL specifies both the spectrum and 1/3 octave band adjustability so an installer can tune the curve to the room.

[!TIP] S06 Part 2 is a compounding point, not a new requirement — it pays for combining isolation or absorption with masking. That reflects acoustic reality: masking alone in a highly reverberant, poorly isolated open plan is a losing battle, whereas masking layered on top of absorptive surfaces (S05) or isolated walls (S03) delivers genuine privacy. Note that S05 documents from Precertification carry forward, which is an unusual and generous administrative allowance.