In May 2023, a former Apple engineer filed a lawsuit alleging that the open-plan layout of Apple Park had made it impossible to conduct confidential work conversations without being overheard by colleagues. The suit, which raised employment law claims unrelated to acoustics, nonetheless contained a specific complaint that the building's design prioritised aesthetics over functional acoustic separation, and that confidential information about unreleased products had been audible across the open work floors.
Apple settled the case, and neither party commented publicly on the acoustic allegations. But the lawsuit was not an isolated anecdote. Bloomberg reported in 2018, shortly after employees began occupying the building, that staff were complaining about the noise levels in the curved floor plates. Wired's coverage of the first year of occupancy included acoustic concerns among the most consistently reported staff grievances. The Washington Post published a piece in 2019 specifically examining how the most valuable technology company in the world had apparently built itself an open-plan office that many employees found acoustically dysfunctional.
The acoustic story of Apple Park is not a straightforward failure narrative. It is a case study in what happens when the most ambitious architectural programme of a generation meets the fundamental physics of sound propagation in open space.
The Building: What Was Built
Apple Park, designed by Foster + Partners under Norman Foster's direction, is the most expensive corporate headquarters ever constructed, at an estimated cost of $5 billion. It occupies a 71-hectare site in Cupertino, California, formerly occupied by Hewlett-Packard facilities. The campus opened in 2017.
The centrepiece is the ring building — internally called the Main Ring or Building 1 — a circular structure 460 metres in diameter with a perimeter of approximately 1.6 km. The ring is four storeys above grade with one basement level. Total floor area: approximately 260,000 m². Occupancy: approximately 12,000 employees.
The architectural concept was maximal continuity: the ring describes a closed loop with no primary entrance or exit, reinforcing the idea of the building as a unified gesture rather than a collection of workplaces. The structural system uses a concrete core with long-span steel floor plates extending outward, allowing the façade to be entirely glass — both the exterior curved glass curtain wall and the interior glass wall facing the central garden courtyard.
The interior floor plates are deliberately open. There are no conventional office partitions. Work areas are organised as "pods" — clusters of desks arranged on the open floor — separated by support spaces (meeting rooms, phone booths, kitchens) located in the inner and outer zones adjacent to the glass facades. The central working zone of each floor plate is unobstructed from wall to wall, a distance of approximately 20 metres.
The floor plates curve in plan, following the ring geometry. This has acoustic implications: the concave inner wall faces (the interior glass wall facing the garden) can generate focused reflections — the curved surface acts as an acoustic lens, potentially concentrating sound energy from a distributed source onto specific points of the floor plate.
The Acoustic Design Intent
Foster + Partners engaged Arup Acoustics as acoustic consultants for Apple Park. The published scope of acoustic work covered building services noise control, the auditorium (Steve Jobs Theater), and coordination with the overall design team.
The specific acoustic treatment of the open-plan work floors is not publicly documented in detail. What is visible from photographs and published descriptions includes:
Ceiling system: The main floor plates feature a bespoke timber ceiling system with timber ribs and recessed lighting. Timber is acoustically reflective (NRC approximately 0.10–0.15 for smooth timber surfaces). The ceiling is not a high-absorption system — it is an architectural finish that prioritises appearance.
Flooring: Smooth concrete or polished timber-effect flooring in working areas. NRC < 0.05. Acoustically reflective.
Walls: Glass to the exterior (NRC < 0.05) and interior (NRC < 0.05). Some areas have meeting room enclosures with acoustic glazing, but these are positioned at the perimeter zones.
Furniture: Open-plan desk furniture with minimal acoustic screening. Standard acoustic desking with low panels (600–800 mm above desk level) provides negligible speech privacy — the panels intercept the direct sound path but do not address the dominant reverberant field.
Based on available documentation and comparable open-plan configurations, the likely acoustic parameters of the main work floors are:
- RT60 at 500 Hz: 0.6–1.0 s (typical for open-plan with reflective ceiling and floor)
- D2,S (spatial decay rate): 3–5 dB per doubling of distance (ISO 3382-3 target: ≥ 7 dB)
- Lp,A,S,4m (equivalent A-weighted sound pressure level at 4 m from a standard talker): 50–55 dBA (ISO 3382-3 privacy target: ≤ 48 dBA)
- Distraction distance (rD): 8–15 m (ISO 3382-3 target: < 5 m for acceptable open-plan performance)
Use AcousPlan's speech privacy calculator to model comparable open-plan configurations and evaluate acoustic performance against ISO 3382-3 targets.
The Curved Floor Plate Problem
The ring geometry creates an acoustic challenge that does not exist in rectangular open-plan floors. The concave interior glass wall — the face of each floor plate that looks toward the central garden — acts as a cylindrical acoustic reflector.
A concave curved surface focuses reflected sound energy toward a focal zone on the opposite side of the reflective arc. For a cylindrical curve of radius R, the focal distance is R/2. The interior glass wall of the Apple Park ring has a radius of approximately 190 metres (the interior radius of the ring). The focal distance would therefore be approximately 95 metres — well beyond the width of the floor plate.
This means the curved glass wall does not create a sharp acoustic focal point within the floor plate. However, it does create a concentrated reflected field: sound reaching the interior glass wall from the working zone is reflected back in a focused rather than scattered pattern, contributing to elevated reverberant levels in the central working area. This is distinct from the behaviour of a flat reflective wall, which would scatter reflected energy more uniformly.
The practical consequence is that the curved geometry increases the effective reverberation in the direction of the interior wall beyond what would be predicted from simple room acoustic models. The speech propagation curves — the fall-off of speech intelligibility with distance — are shallower in the direction toward the inner glass wall than in the direction away from it.
For a space designed around confidentiality and the handling of commercially sensitive information about unreleased products, this is a structurally problematic acoustic characteristic.
What Sound Masking Can and Cannot Do
The standard intervention for inadequate speech privacy in open-plan offices is sound masking — the introduction of a shaped broadband noise field (typically pink noise spectrally adjusted to mimic HVAC sound) at a level of 40–48 dBA, which reduces the intelligibility of speech by reducing the signal-to-noise ratio.
Sound masking works. At Apple Park's estimated D2,S of 3–5 dB, masking at 42–45 dBA would reduce the effective distraction distance (rD) from an estimated 12 m to approximately 6–7 m — a meaningful improvement, though still above the ISO 3382-3 target of 5 m.
However, masking has limitations that are particularly relevant to Apple Park's context:
Masking does not improve the acoustic environment — it makes it louder. Raising the ambient noise floor to mask conversation also raises the level at which all conversations must be conducted to remain intelligible to nearby intended listeners. In a space where acoustic fatigue is already a reported concern, masking can worsen the experience of sustained work.
Masking cannot compensate for extreme D2,S deficits. If D2,S is 3 dB — at the lower end of the estimated range — masking can reduce distraction distances but cannot create a genuinely private environment. Speech remains intelligible at moderate distances even with masking active at 48 dBA.
Masking cannot address focused reflections. The curved glass wall reflection path is a specular phenomenon — it creates identifiable echoes at specific locations, not a diffuse reverberant field. Sound masking is ineffective against discrete reflection paths.
The appropriate acoustic remedy for Apple Park's floor plates — had it been applied — would have been:
- High-absorption ceiling treatment: Replacing or supplementing the timber ceiling with panels achieving NRC ≥ 0.80 across the 125 Hz–4 kHz range. Target ceiling absorption coverage: 70–80% of total ceiling area. Expected D2,S improvement: 2–3 dB.
- Scattering elements on the inner glass wall: Diffuser panels or textured acoustic surfaces on the interior glass wall to disrupt the focused reflection path. A QRD (quadratic residue diffuser) system with well depth sequence optimised for 500–2000 Hz would be appropriate.
- Acoustic furniture screening: High-back seating clusters and desk screens with NRC ≥ 0.60 at desk-level. Expected improvement to rD: 2–3 m reduction.
- Sound masking at 42–45 dBA as a supplement to absorption improvements, not as a standalone remedy.
The Architect-Acoustic Conflict: A Structural Problem
The Apple Park situation illustrates a tension that is endemic to high-profile architecture: the priorities of architectural design and acoustic performance are often in direct conflict, and acoustic performance typically loses.
Norman Foster's design concept for Apple Park was maximum transparency and openness — a building that expresses its values of collaboration and connection through visual and physical openness. Partitions, high-absorption ceiling panels, and acoustic barriers are antithetical to this concept. They interrupt sightlines, introduce visual complexity, and signal separation rather than connection.
This is not a criticism of Foster + Partners. It is a description of the fundamental problem. An architect whose brief is to create the most open, transparent, visually unified workspace in history will resist acoustic interventions that compromise that openness. The acoustic consultant's role in this dynamic is to find solutions that achieve acoustic targets within the architectural concept, or to document clearly the acoustic consequences of not doing so.
What Apple Park suggests — though without internal documentation we cannot know this — is that the acoustic consequences of the design concept were either not fully evaluated at the design stage, or were evaluated and accepted as a consequence of the overriding architectural priorities.
This is common. A 2021 survey by CIBSE (Chartered Institution of Building Services Engineers) found that acoustic performance was listed as the primary post-occupancy complaint in 43% of new open-plan office buildings — more than any other environmental quality metric. The buildings with the worst acoustic performance were disproportionately those where the architectural concept was built around openness and visual connection.
The $5 Billion Lesson
Apple Park cost $5 billion. If a 1% allocation of that cost — $50 million — had been dedicated specifically to acoustic performance in the main ring building, the outcome would have been very different. High-performance acoustic ceiling systems, diffusion treatment on the curved glass walls, and properly calibrated sound masking could have been specified from the outset and integrated into the architectural design rather than retrofitted.
The reason this did not happen is not budget — Apple can afford it. The reason is that acoustic performance was not positioned as a first-order design priority from the project outset. It was treated as a technical requirement to be managed, not a design goal to be optimised.
The consequence is a building that is, by architectural measures, one of the most remarkable corporate spaces ever created, and that houses 12,000 people in an acoustic environment that many of them find distracting, fatiguing, or incompatible with confidential work.
Lessons for Large-Scale Open-Plan Design
Apple Park's acoustic experience, mediated through its exceptional scale and architectural ambition, contains lessons applicable to any large open-plan workspace:
D2,S is the key metric. Before designing or specifying an open-plan office, measure or model D2,S. A target of ≥ 7 dB is achievable with proper acoustic design. Below 5 dB, speech privacy is functionally impossible regardless of masking or furniture interventions.
Curved geometry requires specialist acoustic analysis. Any floor plate with concave curved surfaces — common in architecturally ambitious commercial buildings — requires ray-tracing analysis to identify focused reflection paths. These paths must be treated with diffusive surfaces, not ignored.
Volume drives acoustic performance. Apple Park's floor plates are approximately 4.5 m floor-to-ceiling — generous by commercial standards. Higher ceilings increase the volume above each desk, which is acoustically beneficial. But higher ceilings also mean more ceiling surface area to treat, and a larger reverberant volume to control.
Post-occupancy remediation is expensive and incomplete. The correct time to specify acoustic performance is at design stage. Every dollar spent on post-occupancy acoustic remediation in an open-plan building costs three to five times more than equivalent performance specified during design, because the architectural finishes must be worked around or replaced.
Confidentiality requirements drive the standard. For an organisation whose competitive position depends on secrecy about unreleased products, the acoustic standard should be ISO 3382-3 open-plan office classification A or B. This should be a project brief requirement, not an aspiration. If the architectural design concept is incompatible with that standard, the conflict must be resolved before planning — not after 12,000 employees move in.
Apple Park is many things: an engineering marvel, an architectural statement, a monument to a particular vision of how people should work together. It is also a case study in what happens when acoustic performance is underspecified in a building where acoustic performance matters enormously. The building's beauty is not in question. What is in question is whether that beauty was worth the acoustic cost — and whether the people working there every day would answer that question the same way as the architects who designed it.