Every offshore platform has a story like this. A topsides layout gets signed off at FEED. Then someone raises a flag: the compressor deck exceeds 95 dB(A) at the nearest occupied area, and sleeping quarters sit 18 metres away. Fixing the problem at that stage costs five times what it would have at concept. A noise allocation report, done early and properly, is precisely what prevents that conversation.
What Is a Noise Allocation Report?
A noise allocation report is a formal engineering document that distributes permissible acoustic output across individual equipment items so that the cumulative sound pressure level (SPL) at defined receiver locations does not breach regulatory or project-specified limits. It is produced during the design phase and forms part of the HSE deliverable package.
The word “allocation” is key. The report doesn’t simply measure noise it engineers it. Each piece of equipment is assigned to a maximum allowable SPL contribution. Together, those allocations create a facility-wide acoustic envelope that satisfies occupational exposure limits and, where relevant, community boundary noise criteria.
This is fundamentally different from a post-construction noise survey. The noise allocation report is a predictive, design-controlling document.
The Regulatory Framework Behind Every Noise Allocation Report
Noise allocation reports are governed by OSHA 29 CFR 1910.95 (85/90 dB(A) TWA limits), IEC 60534-8-3 for control valve noise prediction, ISO 9613-2 for sound propagation modelling, and offshore-specific codes including the UK HSE Noise at Work Regulations 2005 and NORSOK S-002 for Norwegian shelf installations.
OSHA 29 CFR 1910.95 sets an 8-hour TWA action level of 85 dB(A) and a permissible exposure limit (PEL) of 90 dB(A). Above 85 dB(A), a formal hearing conservation program is legally required. Above 90 dB(A), engineering controls are mandatory not optional.
IEC 60534-8-3 governs aerodynamic and hydrodynamic noise prediction from control valves. In our experience reviewing FEED packages, control valve noise is routinely underestimated and then emerges as a compliance problem during detailed design.
For UK offshore installations, the HSE Noise at Work Regulations 2005 imposes a first action level of 80 dB(A) LEP,d 5 dB(A) stricter than OSHA’s US threshold. HSE noise compliance offshore is considerably more demanding given enclosed deck geometry and adjacent habitation.
Recognized for excellence.
PROJECTS DELIVERED ACROSS THE GLOBE
What Happens When You Skip the Standards?
Non-compliance is not a paperwork problem. Retrofitting acoustic enclosures or silencers post-construction costs 3–5× the equivalent FEED-stage solution. Worker compensation claims for noise-induced hearing loss have cost North Sea operators tens of millions of pounds in aggregate. Regulatory shutdown of a producing asset is possible where noise assessments are absent from the safety case.
How a Noise Allocation Report Is Actually Built ?
A noise allocation report is built in three phases: a complete equipment noise source inventory with predicted SPL values; 3D acoustic propagation modelling per ISO 9613-2 producing industrial noise contour maps; and iterative budget allocation that assigns maximum allowable output per equipment item and specifies any required acoustic mitigation.
- Equipment Noise Source Inventory
Every source is catalogued: rotating machinery (turbines, compressors, pumps), pressure let-down equipment (PRVs, control valves, chokes), fired heaters, flare stacks, and HVAC systems. Preliminary SPL values come from vendor data sheets or from IEC 60534-8-3 predictions for unspecified control valves. The output is a source inventory table: tag, noise power level (LW), octave band breakdown, and directivity.
- Noise Propagation Modelling
Each source is placed at its design location and SPL contributions are calculated at defined receiver points using ISO 9613-2 methodology. Software such as SoundPLAN or CadnaA renders results as industrial noise contour maps colour-coded overlays on the plot plan at 1.5m working height. The noise dose calculation then converts predicted levels into 8-hour TWA values per occupied work zone.
- Budget Allocation and Mitigation Hierarchy
Exceedances are identified, dominant contributors pinpointed, and tightened equipment noise budgets assigned. Mitigation follows a strict hierarchy: source control first, then path (enclosures, barriers, distance), then receiver (PPE) as a last resort only. The final allocation matrix becomes a binding procurement specification vendors must guarantee compliance as a FAT condition.
Where Noise Allocation Reports Fit in the Project Lifecycle?
A noise allocation report belongs at FEED the stage where equipment selection and layout are still flexible and changes are cheap. By detailed design, the plot plan is largely fixed and vendor orders are placed, leaving only constrained mitigation options. Post-construction acoustic retrofits cost 3–5× the equivalent FEED-stage design change.
| Project Stage | Mitigation Cost | Design Flexibility |
| Pre-FEED / Concept | Lowest | Very high layout and equipment type still open |
| FEED | Low to moderate | High specification changes still possible |
| Detailed Design | Moderate | Moderate silencers and enclosures can be added |
| Construction | High | Low structural modifications required |
| Commissioning / Operations | Very high | Very low shutdown often required for retrofits |
Noise Allocation in Offshore vs. Onshore Facilities
Offshore noise allocation is governed by stricter limits UK HSE mandates 80 dB(A) first action level vs. OSHA’s 85 dB(A) due to enclosed deck geometry, reflective surfaces, and proximity of sleeping quarters to rotating equipment. Onshore facilities additionally require community boundary noise modelling where residential receptors are within impact range.
Offshore platforms present the most acoustically demanding environments in the industry. Enclosed or semi-enclosed decks create reverberant fields. Workers on 12-hour shifts across 14- or 28-day hitches accumulate significant noise dose. NORSOK S-002 caps sleeping cabin levels at 60 dB(A) and control rooms at 75 dB(A). Industrial noise contour mapping on a topsides often requires 3D modelling beyond ISO 9613-2’s open-field assumptions.
Onshore facilities refineries, gas processing plants, LNG terminals face an additional constraint: local authority planning conditions that cap noise at the nearest residential receptor. The noise allocation report for an onshore facility must satisfy both occupational and community limits simultaneously.
Frequently Asked Questions
A noise allocation report distributes permissible acoustic output across facility equipment so cumulative noise levels at occupied areas comply with OSHA 1910.95, HSE, or project-specific limits. It is a design-stage document that prevents non-compliance before construction and eliminates costly acoustic retrofits.
It should be initiated at FEED ideally pre-FEED for large facilities. This is when equipment selection and plot layout are still flexible. Conducting the study at FEED ensures acoustic mitigations are designed in, not bolted on, avoiding the 3–5× cost premium of post-construction retrofits.
Key standards include OSHA 29 CFR 1910.95 (US), HSE Noise at Work Regulations 2005 (UK offshore), IEC 60534-8-3 for control valve noise prediction, ISO 9613-2 for outdoor sound propagation, and NORSOK S-002 for Norwegian shelf installations.
An equipment noise budget is the maximum allowable SPL assigned to a specific piece of equipment so its combined contribution with all other sources does not exceed the facility’s overall noise target at defined receiver locations. It becomes a binding vendor specification enforced at FAT.
A noise survey measures actual SPL levels at an existing facility. A noise allocation report predicts noise levels at the design stage and assigns acoustic budgets to control them. One is diagnostic; the other is preventive and far more valuable because it’s done while change is still cheap.
Noise contour maps overlay predicted SPL contours on the facility plot plan at working height. They identify zones exceeding occupational limits, guide equipment repositioning, and quantify the acoustic benefit of proposed barriers or enclosures all before any steel is erected on site.
OSHA 29 CFR 1910.95 mandates engineering controls where noise exposures exceed 90 dB(A) TWA. While OSHA does not prescribe the specific format, demonstrating compliance with engineering controls requires the systematic acoustic design analysis that a noise allocation report provides.
iFluids Engineering provides noise allocation studies, acoustic engineering, and HSE compliance support across oil and gas, petrochemical, and offshore projects. Contact our acoustic engineering team to discuss your project requirements.