Industrial Noise Control: A Complete Guide for Factories

Factories, workshops, plant rooms and process facilities are among the loudest workplaces there are. Compressors, presses, fans, pumps, conveyors and generators run for hours, and the people who operate and maintain them are exposed every shift. Industrial noise control reduces machinery noise to:

• Protect workers' hearing

• Improve communication and safety on the floor

• Keep noise inside the site boundary

The scale of the problem

The U.S. National Institute for Occupational Safety and Health (NIOSH) estimates that 22 million U.S. workers are exposed to hazardous noise on the job each year, according to a 2023 review of fifty years of its research in Seminars in Hearing. Noise-induced hearing loss is permanent, which is why prevention comes first.

Learn more about common sources of industrial noise to understand its role in acoustic design.

Exposure limits at a glance

Workplace limits are daily exposures averaged over a working day:

• OSHA (USA), 29 CFR 1910.95 — permissible exposure limit of 90 dBA over 8 hours; hearing conservation program required from 85 dBA; impulse noise should not exceed a 140 dB peak.

• NIOSH (USA) recommendation — 85 dBA over 8 hours with a 3 dB exchange rate — and even then, about 8% of workers could still develop hearing loss.

• European Union, Directive 2003/10/EC — lower action value 80 dB(A), upper action value 85 dB(A), exposure limit value 87 dB(A) accounting for hearing protection.

Projects in the Kingdom should be assessed against the occupational health and safety requirements that apply locally; these international limits show what each level means.

• Site boundary noise in Saudi Arabia — the Ministry of Environment, Water and Agriculture began implementing a national noise regulation in June 2021, with penalties including non-compliance with approved noise times and permissible levels and failing to provide monitoring data to the National Center for Environmental Compliance.

Learn more about let the plant breathe to understand its role in acoustic design.

Engineering controls come first

Every major framework puts engineering controls ahead of hearing protection:

• OSHA — feasible administrative or engineering controls must be used when limits are exceeded; hearing protection is provided where those controls fail.

• EU Directive — risks must be reduced at source through working methods, equipment and technical measures such as shields and noise-absorbing coverings.

• NIOSH — reduce the hazard through engineering before relying on personal protective equipment.

Source, path, receiver

The OSHA Technical Manual organises noise control into three stages:

1. Source — change the machine or process.

2. Path — put something between the noise and the people or boundary.

3. Receiver — protect the worker.

Stage 1 — Controlling noise at the source

Measures listed in the OSHA Technical Manual include:

• Reducing mechanical impact energy

• Optimising equipment speed and maintaining balance

• Vibration isolation — decoupling vibrating machinery from the structure.

• Vibration damping — on metal panels, up to 30 dB of noise reduction where vibrating panels are the radiator.

Real example: NIOSH's review reports that coating the conveyor flight bars of continuous mining machines with urethane reduced operator noise by about 7 dB.

Stage 2 — Controlling noise along the path

Path controls from the OSHA Technical Manual, and where each fits:

• Acoustic enclosures — contain compressors, pumps and generators, with access doors and ventilation.

• Barriers — shield workstations from a line of noisy machines.

• Silencers and attenuators — reduce noise in ducts and pneumatic systems.

• Acoustic lagging — reduces noise radiated from pipes and ducts.

• Acoustic louvres — let plant breathe while reducing noise through openings.

Absorption has a limited role: NRC Canada research shows doubling a hall's absorption lowers the reverberant level by about 3 dB, and does not change levels for operators right beside their machines. Ceilings, baffles and wall panels help workers further away; they do not replace enclosures and barriers.

Louvres need care too. Research at the Australian Acoustical Society's Acoustics 2018 conference found louvre performance is limited at low frequencies by mass and at high frequencies by blade gaps, and that tighter blade spacing quickly raises pressure drop beyond what plant fans can tolerate.

Stage 3 — Controlling noise at the receiver

• Quiet control rooms and refuges — from which operators supervise machinery.

• Acoustic booths — at fixed workstations.

• Work organisation — limiting time spent in the loudest areas.

• Hearing protection — the final layer, not the first.

Running an industrial noise control project

1. Survey — measure sound levels across the floor, at workstations and at the boundary.

2. Rank the sources — treating the second-loudest machine achieves little while the loudest still dominates.

3. Select controls — from source, path and receiver options, allowing for maintenance access, ventilation and safety.

4. Implement — install and commission the measures.

5. Verify — measure again to confirm the reduction achieved.

Understanding soundproofing cost can help you plan an effective solution for reducing unwanted noise.

The AcouStick approach

AcouStick supplies and installs the main products used in industrial noise control:

• Containment — Acoustic Enclosures, Mass Loaded Vinyl and Acoustic Doors

• Plant and ventilation — Acoustic Louvers, Sound Attenuators and Acoustic Lagging

• Large-space absorption — Acoustic Baffles, Acoustic Wool Panels and Acoustic Perforated Metal Panels

• Worker protection — Acoustic Booths

If machinery noise on your site is too high for workers or neighbours, AcouStick can help you identify the dominant sources and specify enclosures, barriers, louvres and absorption to bring it down.

Email: info@acoustick.co | Call: +966 51 130 809 | Web: www.acoustick.co

REFERENCES

• Themann, C.L., Masterson, E.A., Peterson, J.S., & Murphy, W.J. "Preventing Occupational Hearing Loss: 50 Years of Research and Recommendations from the National Institute for Occupational Safety and Health." Seminars in Hearing, 44(4), 2023: pmc.ncbi.nlm.nih.gov/articles/PMC10562059

• U.S. Occupational Safety and Health Administration. 29 CFR 1910.95, "Occupational noise exposure": osha.gov/laws-regs/regulations/standardnumber/1910/1910.95

• Kardous, C., et al. "Understanding Noise Exposure Limits: Occupational vs. General Environmental Noise." NIOSH Science Blog, CDC, 8 February 2016: cdc.gov/niosh/bulletin/2016/noise.html

• European Agency for Safety and Health at Work (EU-OSHA). Directive 2003/10/EC — noise (minimum health and safety requirements regarding exposure of workers to noise): osha.europa.eu/en/legislation/directives/82

• Saudi Gazette. "Environment ministry begins implementation of noise regulation across Saudi Arabia." 2 June 2021: saudigazette.com.sa/article/607325

• U.S. Occupational Safety and Health Administration. OSHA Technical Manual, Section III, Chapter 5: "Noise": osha.gov/otm/section-3-health-hazards/chapter-5

• Warnock, A.C.C. "Reverberant Noise Control in Rooms Using Sound Absorbing Materials." Building Research Note, National Research Council Canada, June 1980: nrc-publications.canada.ca

• Hayne, M., Tan, D., Devereux, R., & Mee, D. "Testing and Performance Quantification of Acoustic Louvres." Proceedings of Acoustics 2018, Australian Acoustical Society, Adelaide: acoustics.asn.au/conference_proceedings/AAS2018/papers/p54.pdf