How Sownd Certification Works

Sownd Certification is the standard for audio inclusivity in the built environment. It exists because 1 in 3 people are noise-sensitive - hearing loss, tinnitus, ADHD, autism, age (RNID, 2025; Akeroyd & Munro, 2024, International Journal of Audiology) - and the spaces we design, build and operate are made for the other two. Not because acoustics are ignored, but because there has been no consistent way to prove they were considered, or for the people who need it to find the spaces that work for them.

The certification works across three tiers. Each asks a different question of a space:

Bronze - Acoustic Comfort. Is the space right? The acoustic environment, independently verified against human-centred thresholds. In plain terms: a Bronze space is one where people can hold a conversation, including the 1 in 3 who find that hardest.
Silver - Operations and Behaviour. Is it run inclusively, for the people actually in it? Operations tuned to the occupants: monitoring, training, protocols, and their own anonymous feedback.
Gold - Experience and Technology. Can everyone take part fully? Hearing access technology, acoustic zoning and sensory design, so participation does not depend on typical hearing.

The tiers measure depth of assessment, not quality. A Bronze space is not a lesser space. It is a verified one.

Certification is performance-based: a space passes on its measured performance, not on which products were installed.

What Bronze is.

Bronze is an easy-to-understand, easy-to-specify acoustic requirement. It lets architects and their clients agree the expected acoustic performance of a space, then verify it has been achieved. This framework is written for built environment professionals: architects, acoustic consultants, designers and operators. The certificate on the door is what the people using the space see; the framework behind it is what you specify against. Specifiable from RIBA Stage 2, proven at completion.

Silver and Gold criteria are published as separate framework documents, so the Bronze pack stays specifiable at a desk in one sitting.

The Public Certification

This framework is written for built environment professionals. The certificate it produces is written for everyone else. That is the point of the whole scheme: 1 in 3 people are noise-sensitive, and until now they have had no way to know whether a space will work for them before walking in. The certification exists so they can choose.

What is public. Every certified venue gets a live certificate page showing: the certified spaces and their results; plain-English notes on what to expect, including any declared limitations such as street noise or equipment noise; how each space achieves its rating; the framework version, assessment route, assessor and validity dates. The certificate covers the spaces put forward for assessment, not the whole building. No login, no paywall. Anyone can read it.

What each tier tells you - and what it does not. Every certificate states plainly which tier the space holds, what that tier covers, and what it does not.

Bronze speaks for the acoustic fabric: reverberation and background noise, verified. It does not promise a quiet Friday night, manage behaviour, or cover amplified sound.
Silverspeaks for how the space is run: monitoring, trained staff, protocols, and the occupants' own anonymous feedback. It does not change the physics beyond Bronze.
Gold speaks for the full experience: hearing access technology, zoning, sensory design. It is the only tier that claims the experience layer.

A certified room can still have a bad day. The certificate tells you what was verified and what to expect; it does not guarantee comfort under every condition, and it says so.

Who it is for. The person choosing where to eat, work or meet: someone with hearing loss deciding if they will be able to follow the conversation, a parent of an autistic child checking a venue before a birthday, a team lead booking a workspace that will not exhaust half the team. They do not complain when a space fails them. They just do not come back. The certificate gives them the information before the visit, not the regret after it.

How it is made public.

At the door: a plaque or window sticker carrying the mark and a QR code that opens the live certificate.
Online: the certified directory at sownd.co.uk, listing every certified space.
Over time: certificates stay live. Annual review keeps them current; the framework version on the certificate records exactly what the space was assessed against.

One badge, one scan, no standards numbers required. That is also what makes it work in the other direction: anyone can ask a venue, landlord or council to insist on it.

Who Verifies a Certification

Every Sownd certification is reviewed by an independent acoustic consultant against the framework's threshold criteria. Verification is not self-declared.

The Sownd Certification Framework is maintained in partnership with the Institute of Sound and Vibration Research (ISVR) at the University of Southampton. Current certifications are reviewed by:

Dr Daniel Lurcock - CEng, MIOA

Principal Consulting Engineer, ISVR Consulting, University of Southampton

Acoustic reports submitted for certification are reviewed against the thresholds and methodology described below. The assessor confirms whether the evidence supplied - typically post-installation measurements or validated predictive data - meets the Bronze pass criteria for each space and its declared use type.

Scope & Sampling - What Gets Certified

A Sownd certification applies to a defined set of spaces within a venue. It does not, by default, apply to the entire building.

Each certification lists:

Total spaces at the venue - how many spaces exist in the scope the client asked to be considered.
Spaces assessed - how many of those spaces were measured or modelled and submitted for review.
Space-level outcomes - each assessed space is marked individually as Certified, Certified with notes, Not Applicable, or Under audit.

A venue's tier (Bronze, Silver, Gold) reflects the outcome for the assessed spaces. Where only a sample of spaces has been assessed, that is stated plainly on the certification so that visitors, clients, and specifiers can see exactly what has and has not been verified.

Bronze is intended for unamplified conversational environments and informal gathering zones. It is not applied to - and is not a substitute for - sound insulation/privacy assessment (DnT,w / Rw), façade/environmental noise compliance, or amplified-sound management.

Methodology

A space is awarded Bronze when its reverberation meets the threshold for its declared use type, with background noise assessed against the same table and disclosed on the certification where it sits above the recommended level.

There are two routes to that evidence.

Measured route (the standard route)

Post-installation measurements taken by the project acoustic consultant, submitted in the standard Stage 3 / Stage 4 acoustic report, and cross-referenced against the threshold table. This route is open to any acoustic solution. If the space meets the thresholds, it certifies. You do not need an approved product to achieve Bronze.

Approved-solution route (the shortcut)

Where a pre-validated design-and-installation procedure has been applied as designed, the space can be awarded Bronze without a post-installation reverberation measurement. The shortcut exists because the work of proving performance has been done in advance: the system's acoustic performance, prediction approach, installation reliability and quality control are validated before approval, and installation is cross-checked with the installer on every project. Each approved solution carries its own validation rule.

The first approved solution is SonaSpray acoustic finishes (Oscar Acoustics), specified by the project acoustic consultant. Responsibility for confirming product type, thickness, coverage and detailing stays with the consultant. Further approved solutions are being added, each with its own rule.

Background noise on the approved-solution route. Absorption controls reverberation; it cannot quieten an air-handling unit. Where the design-stage acoustic report identifies expected background noise above the recommended level from known equipment, the space can still certify, and that expectation is declared on the certification so visitors and staff know what they are walking into. Managing expectations honestly is part of the standard.

A note on masking. Adding noise to cover noise does not satisfy Bronze on its own. Masking divides the very community this standard serves, and its effect on hearing-aid users is unresolved. PAS 6463:2022 takes the same position: it advises review before installing sound-masking systems or manufactured soundscapes (10.4) and specialist consultation before introducing white noise or background music (Annex A.3).

Who Does What, When

Certification follows the project, not the other way round.

The client asks for it.

"We want this space Sownd Certified" is the whole brief. Any stage, though earlier is cheaper.

The architect specifies it.

From RIBA Stage 2–3, alongside BREEAM and the rest of the certification stack.

The acoustic consultant sets the targets.

Thresholds per space type, straight from the threshold table below, into the acoustic report.

The contractor builds it.

Approved solutions are cross-checked with the installer; everything else gets measured.

The evidence is reviewed.

The independent assessor confirms each space against its thresholds. Nominations are reviewed within 3–5 working days.

The space is certified.

Plaque on the door, QR to the live certificate, space-by-space results published.

It stays live.

Annual review; physical re-assessment if the space materially changes.

The same list works in the other direction: anyone can ask a landlord, employer or council to insist on it. One badge, one sentence, no standards numbers required.

What's Measured

Bronze draws on two primary acoustic quantities:

Reverberation time (Tmf)

The arithmetic mean of reverberation time across the 500 Hz, 1000 Hz, and 2000 Hz octave bands. This is the speech frequency range, and controlling reverberation here is the single biggest lever on conversational clarity.

Background noise (NR / LAeq)

Expressed as an NR rating (preferred) or LAeq, for steady-state internal noise. This typically covers building services and ambient noise, not amplified sound or transient events.

A note on Tmf in open-plan and high-ceilinged spaces. Strictly, a large open-plan floor or a high-ceilinged space such as an atrium has no single reverberation time: sound decays differently depending on where you stand, and tall volumes behave differently again. Bronze uses Tmf as a practical indicator in these spaces, not a physical absolute. ISO 3382-3 descriptors (spatial decay rate, distraction distance) are introduced at Silver and Gold.

Measured spaces are tested in unoccupied conditions, in line with standard acoustic reporting practice, so the verified performance reflects the space's design rather than one specific day's activity. Where a space is certified on validated design-stage data, the certification says so: predicted values are labelled as predicted, never presented as measurements.

Where provided, octave-band data (125 Hz, 250 Hz, 500 Hz, 1 kHz, 2 kHz, 4 kHz) is included in the full report for transparency. STI and acoustic capacity are not required for Bronze V1.0. Acoustic capacity is the V2.0 ambition: a prediction of how the space behaves as it fills - comfortable at this many people, acceptable at that many - so a certificate can say something about the room on a busy Friday, not just an empty Tuesday.

Certification Thresholds

Certification is decided space by space, never for a whole building. Each space is assessed against the thresholds for its declared use type, and the result is shown on the public certification.

Reverberation is the requirement. A space must meet its Tmf threshold to be certified. Reverberation is the fabric of the space: if it is not controlled, the space is not ready for certification.

Background noise is disclosed, not gated. Where a certified space's background noise sits above the recommended level for its use type, the space can still be certified, and the certification says so, plainly, for the people deciding whether the space works for them: background noise may be above the level recommended for a Sownd Certified space of this type. The note is the point - it is the same honesty rule as the equipment-noise disclosure on the approved-solution route.

Where a metric is absent (for example, at an early reporting stage), certification may be stated as provisional pending confirmation.

NR is the governing metric. LAeq is accepted only where NR data is not reported; where both are reported, NR governs. The alternative exists for report compatibility, not threshold shopping.

Each row carries the source standard's value in the same row, so the difference (or the borrowed source) is visible without cross-referencing.

Space type	Tmf (500–2000 Hz)	NR	LAeq	Reference - reverberation	Reference - background noise	Bronze position
Restaurant / Café	≤ 0.80 s	≤ 35	≤ 40 dB	Rindel (2010): best practice 0.7–0.9 s; PAS 6463 Table 2 (dining): Tmf 0.6–1.0 s	Rindel (2010); PAS 6463 Table 2 (dining): 40–45 dBA unoccupied	Within PAS 6463 and Rindel; at the stricter end on noise; stricter than BS 8233 general guidance
Bar / Informal gathering	≤ 0.70 s	≤ 40	≤ 45 dB	No bar-specific guidance; nearest analogue PAS 6463 Table 2 (dining/social): Tmf 0.6–1.0 s	Nearest analogue PAS 6463 Table 2: ≤ 45 dBA unoccupied; no published NR	Bronze applies the nearest PAS 6463 analogue and adds an NR ceiling where none existed
Open-plan office / Co-working	≤ 0.60 s	≤ 35	≤ 40 dB	BCO 2019 / BS 8233: 0.6–0.8 s	BCO 2019: NR 38–40	Deliberately stricter on both - see note below the table
Meeting room / Cellular office	≤ 0.50 s	≤ 30	≤ 35 dB	BS 8233: 0.4–0.6 s	BS 8233: NR 30	Consistent with the standard
Training / Seminar room	≤ 0.60 s	≤ 30	≤ 35 dB	BB93: ~0.6 s	BB93: NR 30	Consistent with the standard
Healthcare waiting area	≤ 0.60 s	≤ 35	≤ 40 dB	HTM 08-01: implies ≤ 0.6 s	HTM 08-01 Table 2: NR 40	RT consistent; noise deliberately stricter - a waiting room is where hearing your name called matters
Atrium / Circulation (gathering)	≤ 0.80 s	≤ 40	≤ 45 dB	Typically uncontrolled (often > 1.5 s)	Rarely specified	Bronze introduces control
Auditorium / Lecture (informal zones)	≤ 0.70 s	≤ 35	≤ 40 dB	BB93 governs teaching spaces; informal zones uncontrolled	BB93 NR 30 (teaching spaces)	Bronze extends control to the informal zones

Single maximum + too-quiet advisory

Every threshold is a single maximum: the number in the table is the pass criterion. One advisory sits alongside it. Very low background noise is a problem of its own in open-plan and shared spaces: every conversation carries, the radius of distraction grows, and privacy disappears. Where measured background noise falls well below the expectation for the use type, the certification flags it as a design advisory. It is never a fail, and Bronze never requires adding noise to comply. BREEAM Hea 05 frames open-plan noise as a band (45-50 dBA) and WELL penalises spaces for being too quiet for the same reason; Bronze handles the floor problem with an advisory rather than a banded threshold.

Why stricter

Where Bronze is stricter than its source standard, the reason is the design listener. Published standards assume typical hearing, where speech needs to be about 5 dB above the background to follow comfortably. A noise-sensitive listener needs nearer +15 dB (Killion & Niquette 2000; Bradley & Sato 2008; ANSI/ASA S12.60). Bronze sets its thresholds for that listener. That is the difference between designing for the average ear and designing for the 1 in 3.

How space types are defined

Space types are defined by declared use - what the space is for, as stated by the operator and checked at review. Occupancy-dependent criteria (how the space behaves as it fills) arrive with acoustic capacity in V2.0.

A like-for-like comparison

Bronze's Tmf is the same measure PAS 6463:2022 uses in its Table 2 (the arithmetic mean of reverberation time at 500 Hz, 1 kHz and 2 kHz), and both frameworks state unoccupied design values - the comparisons in this table are like for like. PAS 6463 contains no bar-specific category and no NR values; where it is cited for bars it is the nearest analogue (dining/social spaces), stated as such.

Where Bronze departs from a published standard, it is deliberately stricter, and the table says so and why. The thresholds identify spaces that meet a baseline of inclusive conversational usability. They do not define acoustic excellence; that is what the higher tiers and the consultant's own ambitions are for.

The Silver and Gold Tiers

Each tier asks a different question. Bronze asks: is the space right? Silver asks: is it run inclusively, for the people actually in it? Gold asks: can everyone take part fully? Deeper assessment, not a higher score. A Bronze space that never goes further is still a verified space.

Silver - Operations and Behaviour

Silver certifies that the space is managed for audio inclusivity beyond the physics. Sound is subjective and hearing preferences vary: the background level that helps one person concentrate is the level that exhausts another, and no threshold table can settle that. So Silver starts from the people actually in the space, and verifies that operations are tuned to them rather than to an average occupant who does not exist. Silver is assessed annually and covers:

An anonymous occupant survey. Everyone who uses the space regularly, no names collected. It surfaces what no measurement shows: which zones people avoid, which behaviours grate, whether the headsets help or get in the way.
Noise monitoring, by one of three routes sized to the venue: a permanently installed monitor (levels only, never audio); a client-run monitor with periodic reports; or a repeated two-week temporary measurement.
Staff training on how noise affects noise-sensitive and neurodivergent people, refreshed annually.
Behavioural noise protocols - documented, published to staff: door management, equipment scheduling, kitchen and break-area etiquette, meeting room use.
Visual communication - quiet zone markers and transition signage, so the building tells people how to use it.

Design stage or existing space. Where Sownd Certification is specified at design stage, the layout and materials that support inclusivity are considered from the start, alongside the Bronze physics: call booths, breakout rooms, quiet refuges, acoustic variety across the plan. Where the space already exists, Silver and Gold ambitions are assessed for retrofit limitations before the space is operational, so nobody commits to a tier the building cannot deliver. Some of Silver is purely operational and fits any building; the layout that supports it is far cheaper to draw than to retrofit.

Gold - Experience and Technology

Gold certifies a fully audio-inclusive environment: the experience layer, and the technology that delivers it. Where Silver tunes the running of the space to its occupants, Gold removes the remaining barriers to taking part at all: hearing the presentation directly through your hearing aid, finding a zone that matches what you need, knowing a room's acoustic character before you book it. It covers:

Assistive listening technology - Bluetooth Auracast is preferred; hearing loop or equivalent is also accepted - in the spaces where sound is transmitted to people: meeting rooms, conference rooms, reception areas, event spaces. Installed, tested and signposted.
Biophilic soundscapes where the space suits them, typically venues with multiple rooms and zones. Where a space is too small or single-roomed to benefit, that is declared as not suitable rather than counted against the venue.
An acoustic zoning strategy - distinct quiet, collaborative and active zones, with transitions designed rather than accidental. Layout is zoning in embryo: call booths, breakout rooms and areas arranged for different purposes are the start of a Gold zoning strategy, whatever tier the space holds today.
Multi-sensory design - lighting, visual complexity, services noise and thermal comfort reviewed together, aligned with PAS 6463.
User control and choice - quiet rooms and refuge spaces, and booking systems that tell people the acoustic character of a space before they choose it.

A note for design teams: Gold's zoning cannot be retrofitted with technology. If Gold is the ambition, the zoning belongs in the plan from RIBA Stage 2–3. Bronze and most of Silver can be reached in an existing space; Gold is easiest in a space that was designed for it.

Status

Silver and Gold criteria are in technical validation and will be published as separate framework documents, keeping this pack lean enough to specify from in one sitting. The summaries above are the commitments; the pass criteria follow. Pioneers are co-developing both tiers (see The Pioneer Programme).

The Pioneer Programme

The first 50 certified businesses are Pioneers: the founding cohort proving the first standard for audio inclusivity in real spaces, and making it the norm. Pioneer is recognition, not a separate standard. A Pioneer space passes exactly the same Bronze thresholds as any other space; there are no shortcuts on the criteria, because the credibility of the first 50 is the credibility of the whole scheme.

What differs is the terms and the recognition:

Founding Pioneer status, permanently - numbered membership of the First 50.
Certification fees waived for the first two years.
Co-development of Silver and Gold. Pioneers shape the higher tiers as they are specified on new design-stage projects and piloted as retrofits in existing spaces - and are first in line as each tier comes online.
A listing in the First 50 directory and co-marketing with Sownd Affects.
A limited-edition Pioneer plaque, optional - the blue mark, distinct from the tier marks.

On Pioneer certificates, the Pioneer mark leads: it records that this business was one of the first 50. Alongside it sit the tier marks, which populate as the space progresses - Bronze on certification, Silver and Gold as each is achieved, with adopted elements visible along the way.

Adopted elements. Tiers are awarded whole, but progress is visible before a tier completes. A Pioneer certificate can show Silver and Gold elements already in place - "Auracast installed in meeting rooms", "acoustic zoning in place", "staff training delivered" - ahead of the full tier award. And where an element is not suitable for the space, the certificate says so: "biophilic soundscape - not applicable to a single-room office" reads as honesty, not a gap. The same principle as space-by-space results: state what is true, declare what does not apply, claim nothing else.

The Pioneer route is built for projects that have already invested in acoustics. Nominate a completed project with its existing acoustic report; if the spaces meet the thresholds, they certify. The work you have done counts toward the standard.

Review & Recertification

A Sownd certification is not a one-time stamp. It is kept live through an annual review cycle.

Annual confirmation

Each year, the certificate holder is prompted to confirm that no acoustic changes have been made to the certified space. Where changes are reported - by visitors, staff, or anyone using the space - we recommend an audit to bring the certification up to date.

Triggered reassessment

Where three or more reviews report that a space is not as its public certification describes, we get in touch to request confirmation of changes or a reassessment.

In-person inspection at Gold

When a space achieves full Gold, one of our dedicated independent assessors visits the space in person.

Every certification carries a clear Valid Until date and an Annual Review Due date, both visible on the venue's cert page.

Standards Context & Governance

Bronze thresholds are aligned with, and derived from, established acoustic and inclusion standards:

BS 8233:2014 - Guidance on sound insulation and noise reduction for buildings.
BB93 (2015) - Acoustic design of schools: performance standards.
BCO Guide to Specification (2019) - British Council for Offices.
HTM 08-01 (2013) - Acoustics, Health Technical Memorandum series.
PAS 6463:2022 - Design for the mind: neurodiversity and the built environment.
ISO 3382-1:2009 - Measurement of room acoustic parameters.
ISO 3382-3:2022 - Measurement of room acoustic parameters. Part 3: Open plan offices.
ISO 22955:2021 - Acoustics: Acoustic quality of open office spaces.
FIS Guide to Office Acoustics.
Rindel's published work on acoustic capacity (cited for the V2.0 roadmap).

Bronze is a composite of established standards applied consistently, not novel science. Every threshold row in the table above cites its source.

Bronze is differentiated not by inventing new acoustic limits, but by applying consistent conversational-performance expectations across sectors and to space types that are typically unregulated.

Alongside BREEAM and WELL

Sownd does not compete with building-wide schemes; it covers what they leave thin. BREEAM (Hea 05) and WELL (sound credits) score acoustics as one strand of a whole-building assessment written for building owners. Neither tells someone standing at the door anything. Sownd certifies the acoustic experience of specific spaces, in a form the public can read. The schemes stack: specify both, and the acoustic evidence does double duty.

Framework versions

Every certificate states the framework version it was assessed under. Thresholds do not change within a major version; wording and guidance may. A space certified under V1.0 remains certified under V1.0 until its scheduled review. Certification is not revoked by a framework update.

Framework governance

The Sownd Certification Framework is maintained by Sownd Affects. For 2026-27 it is maintained in partnership with ISVR Consulting, University of Southampton. Current framework version: Bronze V1.0 (2026).

Each certification page records the framework version, the measurement standard applied, the assessment route used, and the assessor's name and credentials, so that the basis of every certificate is fully traceable.

What Bronze certification is not

It is not a statutory occupancy limit.
It is not a replacement for fire, building-regulation, or licensing requirements.
It is not a guarantee of comfort under all operating conditions - particularly where amplified sound is introduced or occupancy exceeds design assumptions.
It is not coverage of sound insulation, privacy (DnT,w / Rw), façade noise, or environmental noise compliance.