The WELL Sound Concept Explained

If you're working on a WELL Certification project, then you know the International WELL Building Institute (IWBI) sets requirements for how your building or workplace performs acoustically. Those requirements, along with optional features that earn points toward certification, are outlined in the WELL v2 Sound concept, which covers everything from how a floor plan is zoned and maximum noise levels to sound isolation between rooms and hearing health programs.

In this guide, we'll break down what you need to know about each of the concept's nine features, including what each one requires, how many points it's worth, and how it's verified, plus where continuous sound monitoring fits in today.

What Is the WELL Building Standard Sound Concept?

The Sound concept is one of ten concepts in WELL v2, and it sets requirements for how a building manages background noise, speech privacy, reverberation, impact noise, and hearing health. The IWBI describes its goal as supporting occupant health and well-being by identifying and addressing the acoustic factors that shape how people experience a space.

The concept has nine features: S01 is a precondition every project must meet, and S02 through S09 are optimizations that earn extra points. Together, the optimizations are worth up to 18 points, though WELL v2 counts no more than 12 points from any one concept toward certification. Points earned beyond that cap can count toward the Innovation concept instead.

Note: S07 and S09 are beta features, so projects pursuing them also submit a feedback form that helps the IWBI refine them.

What Does Each WELL Sound Feature Require?

S01: Sound Mapping (Precondition)

S01 requires every project to plan for acoustic problems before they happen by zoning the space and documenting a strategy to manage sound. It has two parts:

Part 1: Label Acoustic Zones. A floor plan or other design document labels each area as one of five zone types:

• Loud zones: areas for loud equipment or activities, such as mechanical rooms, AV/IT closets, kitchens, fitness rooms, and social spaces
• Quiet zones: areas for concentration, rest, wellness, or privacy, such as lactation rooms and nap rooms
• Mixed zones: areas for learning, collaboration, or presentations, such as classrooms and breakout spaces
• Circulation zones: occupiable areas not intended for regular occupancy, such as hallways, stairs, atria, and lobbies
• Not applicable zones: storage rooms, janitor rooms, and other rarely occupied areas without significant noise

Where a loud zone borders a quiet zone, the project also needs a plan to either reprogram those spaces or reduce sound traveling between them. This part is verified by technical document.

Part 2: Provide an Acoustic Design Plan. Projects are required to submit a plan that outlines acoustical solutions and a timeline for putting them in place, focused on managing acoustical comfort, background noise, speech privacy, reverberation time, and/or impact noise. The plan can come from the project team or owner, or take the form of a detailed report from an acoustics professional that also describes existing conditions and measurement results. This part is verified by professional narrative.

S02: Maximum Noise Levels (Up to 3 Points)

S02 caps background noise, meaning the sound from HVAC systems, outdoor noise, and other building sources, based on how each room is used. WELL groups rooms into four categories, each with its own limits:

• Category 1: areas for conferencing, learning, and speaking
• Category 2: enclosed areas for concentration
• Category 3: open areas for concentration, areas with regularly used PA systems, and dining areas
• Category 4: areas with machinery and appliances, such as commercial kitchens, kitchenettes, and labs without lectures

Each category has three limits: an average sound level (Leq) on the A-weighted scale (dBA), an average on the C-weighted scale (dBC), and a 90th percentile level (L10). The C-weighted scale includes more low-frequency sound than the A-weighted scale, and L10 is the level exceeded 10% of the time.

This feature is verified by performance test, with the room unoccupied or at its lowest occupancy, ventilation running normally, sound masking switched off, and windows and doors closed.

S03: Sound Barriers (Up to 3 Points)

S03 requires walls and doors that keep sound, especially speech, from carrying between enclosed rooms. It has two parts, one based on design and one on measured performance.

Part 1: Design for Sound Isolation at Walls and Doors (1 point). Interior walls must meet a minimum sound transmission class (STC) or weighted sound reduction index (Rw), both lab-tested ratings of how well a wall blocks sound, based on what types of spaces it separates. (Note: Projects that install sound masking under S06 Part 1 can use lower targets for most wall types.)

Doors between occupied rooms and doors to mechanical rooms must also have a non-hollow core, be rated at least STC/Rw 30, and be sealed at the head, jamb, and base. This part is verified by technical document.

Part 2: Achieve Sound Isolation at Walls (2 points). Walls between regularly occupied spaces are tested on site using one of two options:

• Option 1, Noise isolation class: Walls must meet a minimum Noise Isolation Class (NIC) or weighted difference level (Dw), which measure how much sound actually drops from one finished room to the next. Targets range from 55 for walls next to loud zones down to 35 for circulation zones, and most are 5 points lower for projects with sound masking.
• Option 2, Speech privacy: The measured NIC or Dw, plus the background sound level in the receiving room, must meet a combined minimum of 70 to 85, depending on which rooms the wall separates.

S04: Reverberation Time (2 Points)

S04 limits how long sound lingers in a room after its source stops, measured as RT60 (the time it takes sound to fade by 60 decibels). Its goal is reverberation times that support speech intelligibility and comfortable vocal effort and are conducive to concentration. The feature applies when the listed room types make up at least 10% of a project's occupiable area.

Rooms with more than one use follow the stricter limit. Projects can show compliance through design (verified by technical document) or by on-site testing (verified by performance test and technical document).

S05: Sound Reducing Surfaces (Up to 2 Points)

S05 requires sound-absorbing materials on ceilings, walls, and workstation partitions to reduce the buildup of speech and other noise. Materials are rated by noise reduction coefficient (NRC) or Alpha-w, both on a scale of 0 to 1 that reflects how much sound a surface absorbs. Like S04, it applies when the listed room types make up at least 10% of occupiable area.

Ceiling coverage is measured against available ceiling area. This feature is verified by technical document.

S06: Minimum Background Sound (Up to 2 Points)

S06 uses dedicated artificial sound, known as sound masking, to raise the background sound to a consistent, steady level. The IWBI notes that this shifts the balance between speech and background sound in favor of acoustical privacy, increasing speech privacy within and between occupied spaces.

Part 1: Provide Minimum Background Sound (1 point). In office spaces, a sound masking system must cover open areas, circulation zones, areas with workstations, and enclosed quiet rooms. It must:

• Produce adjustable output in one-third-octave bands, covering at least 100 Hz to 5 kHz
• Stay at or below 48 dBA in open areas, circulation zones, and workstation areas, and 42 dBA in enclosed quiet rooms
• Be verified by a professional sound masking installer under ASTM E1573-18 or an equivalent standard

This part is verified by technical document.

Part 2: Provide Enhanced Speech Reduction (1 point). Projects earn this point by combining S06 Part 1 with two points from either S03 Part 2 (measured wall isolation) or S05 (sound-absorbing surfaces).

S07: Impact Noise Management, Beta (Up to 3 Points)

S07 reduces impact noise, such as footfall, exercise, or equipment vibration, that travels through floor-ceiling assemblies, by designing resilient floors.

• Part 1: Specify Impact Noise Reducing Flooring (1 point). Floor-ceiling assemblies above or below specific room types, such as quiet zones, areas for concentration and conferencing, fitness areas, and retail and dining areas, must meet a minimum Impact Insulation Class (IIC), either lab-tested or modeled, ranging from 45 to 55 depending on the room type. Verified by technical document.
• Part 2: Meet Thresholds for Impact Noise Rating (up to 2 points). A professional in acoustics measures the finished floor-ceiling assemblies on site. Tier 1 requires a Normalized Impact Sound Rating (NISR) of 42 to 52 for 1 point, and Tier 2 requires 47 to 57 for 2 points, depending on the room type. Verified by technical document.

Both parts also require the beta feedback form, and neither applies to assemblies next to non-occupiable spaces such as roofs or equipment rooms.

S08: Enhanced Audio Devices (Up to 2 Points)

S08 improves speech intelligibility through dedicated, high-performance audio technology and supports individual acoustical needs through organizational policies.

Part 1: Provide Enhanced Speech Intelligibility (1 point). As applicable to the project:

• Rooms for conferencing, distance learning, or hybrid collaboration must have microphones, speakers, cameras, and supporting audio components commissioned by a professional audio engineer.
• Public address systems used daily must be professionally commissioned and achieve a minimum speech transmission index (STI) of 0.50, or a common intelligibility scale (CIS) score of 0.75, in at least half of regularly occupied spaces.
• Speech reinforcement systems must be installed in at least 80% of classrooms and all large presentation spaces.

This part is verified by technical document.

Part 2: Prioritize Audio Devices and Policies (1 point). The organization must meet at least three of the following:

• Employer-provided audio devices are managed by a qualified professional, such as IT, with expectations covered in the employee handbook or onboarding.
• Employees can request alternative arrangements, such as remote work or a different workstation, to meet their acoustic comfort needs.
• Signage shows where quiet and mixed zones are and what they're for, and at least one daily quiet hour is scheduled.
• Employees and distance learners can request speech-enhancing audio devices, such as noise-cancelling headsets, at no cost or with at least a 50% subsidy.

This part is verified by policy.

S09: Hearing Health Conservation, Beta (1 Point)

S09 is aimed at employees who are at risk of occupational hearing loss, such as staff in industrial settings or airports. To earn the point, the project maintains both of the following:

• A hearing health conservation program that provides fitted hearing protection at no cost, complies with OSHA's occupational noise regulations (or the European or regional equivalent), and offers free audiogram tests to employees in loud zones annually, at hiring, before they're first assigned to a hearing-hazardous area, when they're reassigned out of one, and at the end of employment.
• A designated hearing health supervisor who runs at least one hearing health training per year, manages hearing protection and testing equipment, schedules annual audiograms, and audits the program against regulations each year.

Both are verified by policy, plus the beta feedback form.

What Are the Verification Pathways for the WELL Sound Concept?

The WELL v2 Sound concept lists five verification pathways that projects can use to show that each requirement has been met:

• Technical documents: drawings, specifications, product data, or test reports submitted for review
• Professional narratives: a written narrative describing how a requirement is met
• Performance tests: on-site measurements taken by a Performance Testing Agent, following the IWBI's Performance Verification Guidebook
• Policies and operations schedules: written policies showing how the organization supports a requirement
• Beta feature feedback forms: extra documentation for S07 and S09

Can You Use the Sensor Data Verification Pathway to Meet WELL v2 Sound Concept Requirements?

Not directly, as the WELL v2 Sound concept is written today, but projects can apply for an Alternative Adherence Path (AAP) to use sensor data from continuous sound monitors.

Sound isn’t currently among the parameters that can be verified through the sensor data pathway, so features that require performance data can only be verified through an on-site performance test (for example, using a Class 1 sound level meter for feature S02 to measure background noise levels while the space is unoccupied or at its lowest occupancy).

An AAP is an alternative strategy, backed by evidence, that a project submits for approval to show it fully achieves a feature’s intent through a different method. For sound, that means demonstrating that data from continuous monitors fully meets the intent of each feature, such as showing that background noise levels stay within S02’s thresholds. Kaiterra is actively working with customers who are pursuing AAPs using continuous sound monitoring, and we have WELL APs and WELL faculty on staff who can help you navigate the process.

Using sensor data for sound is worth pursuing through an AAP, because continuous data brings benefits of its own. You can see how each space actually sounds day to day as factors like occupancy, HVAC cycles, and equipment use change. Continuous data is key to identifying where acoustic comfort isn't being achieved and confirming whether changes, such as new sound-absorbing surfaces or a sound masking system, keep working over time.

Want to Learn More? Reach Out to a WELL AP on the Kaiterra Team

Whether you're working through the Sound concept for the first time or considering an AAP for continuous sound monitoring, reach out to a WELL AP on our team. We can help you map out which features fit your project and how sound data can support your IEQ goals and improve the occupant experience.