S04: Sound Absorption

(3 points)

INTENT

Design spaces in accordance with comfortable reverberation times that support speech intelligibility and are conducive to focus. 

SUMMARY

This WELL feature requires steps be taken to address acoustical comfort by assigning requirements for surface finishes and reverberation time depending on the room functionality.

ISSUE

In spaces that incorporate hard surface finish materials, reverberation time and reflected sound energy have the potential to build and create uncomfortable environments. For example, a space that is designed for learning, presenting, critical listening or a similar purpose will benefit from having a reverberation time that is conducive to high speech intelligibility and articulation class (i.e., the words or sounds that are intentionally introduced to that space are heard as needed by all occupants). In a classroom, for instance, this requires a reverberation time that is low enough to foster clear speech intelligibility but high enough to allow speech to project to all areas of the classroom. From a universal design and accessibility standpoint, this focus on optimal acoustical design is crucial in designing spaces where all occupants can clearly understand information, sometimes critical information, that is being audibly presented. Over-reverberance and reflected sound energy have the potential to interrupt audio-visual equipment in small spaces, in some instances even making phone calls unintelligible on the receiving and/or source end. There may be instances where enhanced speech intelligibility is not ideal (e.g., office environments, restaurants) where focus or intimacy at a task plane is anticipated. Achieving optimal reverberation times in specific spaces is crucial for designing with acoustical comfort in mind.

SOLUTIONS

Controlling the effects of reverberant and reflected acoustical energy can be achieved via a number of combinations: by designing a space to meet specific reverberation times that are conducive to the intended programming therein, by providing absorptive finishes throughout an enclosure, or a combination of the two. Absorptive finishes can be classified by a number of metrics [e.g., Noise Reduction Coefficient (NRC, α_w or equivalent), Articulation Class (AC)]. For best results, absorptive finishes are provided along surfaces that are located opposite harder surface finishes. If possible, absorption should exist at ceiling planes when floor finishes are programmed to be hard (i.e., wood, polished concrete or similar). Similarly, and where possible, absorptive wall finishes should complement opposite walls that are reflective (e.g., glass office fronts, fenestration).

IMPACT

Designing a space with reverberation time and reflected sound energy in mind can drastically improve the comfort level of occupants in terms of critical listening, speech projection, memory retention and speech privacy.

REQUIREMENTS

Part 1

Meet Thresholds for Reverberation Time (1 point)

Verified by Performance Test

For All Spaces except Dwelling Units

The following is achieved:

1. Spaces meet the maximum RT₍₆₀₎ thresholds in the table below: 

   Room Type	Size	RT(60) (seconds)
   Conference rooms	N/A	≤ 0.6
   Classrooms	< 280 m³ [10,000 ft³]	≤ 0.6
   	Between 280 m³ [10,000 ft³] and 570m³ [20,000 ft³]	0.5 to 0.8
   	> 570 m³ [20,000 ft³]	0.6 to 1.0
   Lecture halls	< 280 m³ [10,000 ft³]	≤ 0.7
   	Between 280 m³ [10,000 ft³] and 570m³ [20,000 ft³]	0.6 to 0.9
   	> 570 m³ [20,000 ft³]	0.7 to 1.3
   Music rehearsal spaces	< 280 m³ [10,000 ft³]	≤ 1.1
   	Between 280 m³ [10,000 ft³] and 570m³ [20,000 ft³]	1.0 to 1.4
   Fitness facilities	< 280 m³ [10,000 ft³]	0.7 to 0.8
   	Between 280 m³ [10,000 ft³] and 570m³ [20,000 ft³]	0.8 to 1.1
   	> 570 m³ [20,000 ft³]	1.0 to 1.8

Part 2

Implement Sound Reducing Ceilings (1 point)

Verified by Design Specifications

For All Spaces except Dwelling Units

Spaces have ceiling finishes that meet the following specifications:

1. Ceiling treatment meets the minimum NRC/ α_w values described below: 

   Space Type	NRC/ αw
   Open Workspaces Enclosed Offices Dining Spaces	0.7 for at least 75% of available ceiling area
   Conference Rooms Classrooms	0.7 for at least 50% of available ceiling area

Part 3

Implement Sound Reducing Vertical Surfaces (1 point)

Verified by Design Specifications

For All Spaces except Dwelling Units

Spaces have wall finishes that meet following requirement:

1. Wall treatments meet the minimum NRC/α_w values described below:

   Space Type	NRC/ αw
   Enclosed offices Dining spaces	0.7 for at least 25% of at least one wall
   Conference rooms Classrooms	0.7 for at least 25% of at least two walls

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