Balancing strict food hygiene regulations with occupational noise control is one of the classic challenges in industrial acoustic engineering. Wet processing facilities, lined with glazed ceramic tiles and stainless steel envelope surfaces, behave essentially as hard reverberation chambers. In such environments, continuous plant noise compounds with repetitive metal on metal impact transients, elevating daily personal noise exposure well beyond statutory thresholds.

Node Acoustics was commissioned to execute a comprehensive occupational noise survey, quantify daily acoustic exposure metrics, and deliver an actionable technical compliance report ready for review by the authorities.

The Acoustic Challenge

The facility operates continuous, parallel production lines across four key departments: curd processing and molding, boiling and cooking lines, manual folding and brining, and automated thermoform packaging.

A site diagnostic identified three primary acoustic mechanisms driving exposure:

Severe Reverberant Build Up: The building envelope relies on typical local industrial construction: reinforced concrete framing, hollow perforated clay brick infill, and vitrified ceramic wall tiles. These surfaces offer virtually zero acoustic absorption, generating prolonged reverberation times that amplify ambient plant noise.

Complex Acoustic Regimes: Personnel face a hybrid noise field: steady state, broadband emissions from roof mounted exhaust extractors and vacuum pumps, overlaid with high amplitude impact transients from stainless steel tray handling and mechanical press strikes.

Hygienic Constraints on Absorption: Conventional acoustic treatment, such as open cell polyurethane foam or unencapsulated mineral wool, cannot be installed in high humidity washdown zones without violating mandatory cleanability and food hygiene criteria.

Measured Exposure Levels and Exceedances:

Baseline continuous ambient levels (LAeq) across the active processing halls ranged between 82.4 dBA and 86.8 dBA, driven by roof mounted extraction fans and vacuum equipment.

Peak sound pressure levels (Lp,Cpeak) from manual stainless steel demolding and trolley handling regularly peaked at 136.2 dBC to 138.4 dBC, approaching the statutory Upper Exposure Action Value of 137 dBC.

Task based exposure modeling established that operators within the Curd Processing and Packaging Homogeneous Exposure Groups reached normalized daily exposure levels (LEX,8h) between 86.2 dBA and 88.7 dBA, exceeding both the Lower Action Value (80 dBA) and the Upper Exposure Action Value (85 dBA) established in Κ.Δ.Π. 317/2006.

Measurement Strategy and Diagnostic Method

The field assessment was executed strictly under CYS EN ISO 9612:2025 (Strategy 1: Task based measurement) using Class 1 integrating averaging sound level meters with real time 1/1 and 1/3 octave spectral logging.

Homogeneous Exposure Groups: Operating staff were stratified into five distinct groups based on operational duties, physical workstation geometry, and mobility throughout the production halls.

Calibrated Exposure Normalization: While plant operational shifts run from 06:00 to 15:00, task analysis isolated non exposed rest breaks totaling 1.0 hour from acoustic energy integration. This established an audited, legally defensible daily exposure duration of precisely 8.0 hours.

In Ear PPE Attenuation Modeling: Sound attenuation across in use Hearing Protection Devices was modeled per CYS EN ISO 4869-2 using octave band calculations and the HML method, applying derating factors per CYS EN 458. This verified that in ear levels were controlled within the target 70 to 75 dBA operational window, avoiding overprotection and preserving audible warning communication on the floor.

Engineering Solutions and Regulatory Compliance

The final technical report provided plant management with a prioritized, source level acoustic action plan aligned with Κ.Δ.Π. 317/2006:

Pneumatic Exhaust Silencing: Specified hygienic, multi chamber porous polyethylene and sintered stainless steel silencers on all localized pneumatic actuators to eliminate sharp directional discharge hisses.

Contact Impact Damping: Specified food contact compliant, high density polyurethane wear strips and non porous elastomeric buffers at metal on metal drop points and trolley guide rails to dampen high frequency impact energy at the source.

Hearing Protection Zones: Formally delineated mandatory hearing protection zones for areas exceeding the 85 dBA Upper Exposure Action Value, accompanied by exact attenuation criteria for procurement.

Audit Ready Technical Report: Compiled complete metrological chains, expanded measurement uncertainty budgets, and machinery mitigation plans into an audit ready compliance deliverable for the authorities.