Occupational Noise Glossary — Key Terms for Workplace Noise Assessment

A reference guide to the key acoustic terms used in occupational noise assessment and SoundPLANmanda documentation.

Key Terms — Noise Levels & Exposure

• LEX,8h — Daily noise exposure level: the equivalent continuous A-weighted sound level normalised to an 8-hour working day. The primary metric for occupational noise compliance under ISO 9612 and EU Directive 2003/10/EC.
• LEX,w — Weekly noise exposure level: the time-weighted average of the daily noise exposure levels over a working week. Used when daily exposure varies significantly.
• LAeq,T — Equivalent continuous A-weighted sound pressure level over measurement period T. The basis for calculating LEX,8h from task or shift measurements.
• LpA,peak — C-weighted peak sound pressure level. Used to assess impulse and impact noise from presses, hammering, gunfire, and explosive events.
• Action values — 80 dBA lower action value (HPE provision required) and 85 dBA upper action value (HPE use mandatory, engineering controls required).
• Limit value — 87 dBA LEX,8h — the exposure level that must never be exceeded at the ear, taking into account the attenuation of hearing protection worn.
• HPE / HPC — Hearing Protection Equipment / Hearing Protection Control. Includes earplugs (foam, pre-formed, custom-moulded) and earmuffs.
• SNR — Single Number Rating: simplified attenuation value for hearing protector selection. Applied using C-weighted noise level minus SNR = estimated A-weighted level at ear.
• HML method — High, Medium, Low spectral correction method for hearing protector selection. More accurate than SNR; requires both A and C weighted measurements.
• Octave band method — Most accurate hearing protector selection method. Uses the full measured noise spectrum (63 Hz–8 kHz) and HPE attenuation data per octave band.
• NIHL — Noise-Induced Hearing Loss: permanent, irreversible sensorineural hearing damage from repeated or prolonged exposure to noise above approximately 85 dBA LEX,8h.

Noise Mapping Terms

• Sound Pressure Level (SPL) — The instantaneous noise level at a given point, measured in decibels (dB or dBA for A-weighted).
• Sound Power Level (LW) — The total acoustic power output of a noise source, independent of distance or environment. Used as input data for noise modeling.
• Noise Map — A color-coded spatial representation of noise levels across a facility or outdoor area, typically at a defined height (e.g., 1.6 m for occupational noise, 4 m for environmental mapping).
• Insertion Loss (IL) — The reduction in noise level achieved by installing a barrier, enclosure, or other control measure. Calculated as the difference in noise level with and without the control.
• Lden — Day-evening-night level: a weighted 24-hour average noise level used for environmental noise and strategic noise mapping under the EU Environmental Noise Directive. Evening and night periods receive additional penalties.
• ISO 9612 — International standard for the determination of occupational noise exposure (engineering method). Defines three measurement strategies: task-based, job-based, and full-shift.

Why Terminology Matters

Using precise acoustic terminology is essential when preparing compliance reports, communicating with regulators, or specifying hearing protection for workers. Confusing LEX,8h with LAeq,T, or applying the wrong HPE selection method, can result in workers being over-exposed or regulators rejecting assessment reports. SoundPLANmanda uses the correct ISO 9612 terminology throughout its calculation and reporting workflows.

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