Overview
ISO/TR 11690-3:1997 - "Acoustics - Recommended practice for the design of low-noise workplaces containing machinery - Part 3: Sound propagation and noise prediction in workrooms" - provides guidance on how sound travels in workrooms and how to predict sound pressure levels at workstations. The Technical Report connects machine noise emissions to noise immission at the workplace, supports communication between machine suppliers and users, and offers a methodology for using noise prediction as an aid to noise control and room acoustical assessment.
Key Topics
- Sound propagation descriptors
- Use of the spatial sound distribution curve to describe how sound levels vary with distance.
- Two summary quantities: the rate of spatial decay per distance doubling (DL2) and the excess level relative to a free field (DLf).
- Room acoustical behavior
- Distinction between diffuse sound fields (where reverberation time relates to level distribution) and non-diffuse or uniform propagation (flat rooms, fitted rooms).
- Identification of near, middle and far regions around a source with characteristic DL2 and DLf ranges (e.g., near-field DL2 ≈ 5–6 dB per doubling).
- Methodology for noise prediction
- A structured prediction workflow: define objectives/target descriptors, collect input data, select an appropriate prediction method, perform calculations, and compare results with targets.
- Input data categories: empty room description (geometry, surface absorption), room fittings (density, distribution, shielding and scattering), and sources (sound power levels, emission sound pressure at workstations, directivity, source dimensions).
- Practical guidance and annexes
- Annexes provide case studies, methods for predicting impact of new machines, procedures for determining workstation levels, and evaluation of acoustical quality.
Applications
ISO/TR 11690-3 is practical for:
- Acoustical consultants and engineers performing noise prediction and room assessments.
- Plant designers and facility managers planning low-noise workplaces with machinery.
- Machine manufacturers and suppliers providing emission data to users.
- Occupational health and safety professionals assessing workplace noise exposure and selecting noise control measures.
Practical uses include comparing mitigation options, estimating the noise impact of new equipment, designing room treatments (absorption, layout, fittings), and verifying that predicted workplace levels meet target criteria.
Related standards
Keywords: acoustics, sound propagation, noise prediction, workrooms, low-noise workplaces, sound pressure level, reverberation time, spatial sound distribution curve, machine noise, noise control.
Open preview (PDF)Acoustics — Recommended practice for the design of low-noise workplaces containing machinery — Part 3: Sound propagation and noise prediction in workrooms