Noise is an unavoidable byproduct of many industrial processes, especially those involving compressed air—such as exhaust from cylinders, solenoid valves, blow-off nozzles, and cooling equipment. As industrial systems become more powerful and compact, efficiency is no longer the only concern. Noise exposure has become a critical safety, health, and compliance issue.
Understanding what dBA means—and how noise is measured and managed—is essential for designing safer factory environments and meeting occupational regulations.
What Is Noise and How Is It Measured?
Noise and vibration are fluctuations in air pressure that affect the human body. When these pressure changes are detected by the human ear, they are perceived as sound. The term noise is used to describe unwanted sound.
Sound is measured using the decibel (dB) scale, a logarithmic scale that represents sound pressure level. Because the scale is logarithmic, small numerical increases represent large increases in sound energy.
Key characteristics of sound measurement:
• Amplitude – the intensity of the sound wave
• Frequency – how fast the wave oscillates
The decibel scale begins at 0 dB, representing the quietest sound a healthy human ear can detect. Every increase of 3 dB doubles the sound energy, even though it may not sound “twice as loud” to the listener.
Sound levels are measured using a sound level meter, and readings depend on:
• Distance from the noise source
• Direction of the noise source
• Indoor vs. outdoor environment (indoor sound reflects and reverberates)
For measurements to be meaningful, distance and test conditions must always be reported.
What Is the Difference Between dB and dBA?
The dBA scale is an A-weighted version of the decibel scale. It adjusts sound measurements to reflect the sensitivity of the human ear, which is less sensitive to very low and very high frequencies.
In practical terms:
• dB measures physical sound pressure
• dBA estimates how loud the sound is perceived by humans
Most occupational noise regulations use dBA, as it correlates more closely with the risk of noise-induced hearing loss.
However, A-weighting can underestimate annoyance and stress caused by low-frequency noise, particularly at higher sound levels. For peak or impulse noise, dBC weighting may sometimes be used, though differences are usually small in industrial settings.
Typical Noise Levels (Approximate)
Examples of common sound levels:
• Breathing: ~10 dBA
• Normal conversation: ~60–65 dBA
• Vacuum cleaner: ~70 dBA
• Busy traffic: ~85 dBA
• Gas mower or hair dryer: ~94 dBA
• Rock concert or chainsaw: ~115 dBA
Because the scale is logarithmic, a sound at 90 dBA is four times as intense as one at 70 dBA.
Occupational Noise Exposure and Hearing Risk
Hearing damage depends on sound intensity and exposure time, not subjective loudness. Louder sounds cause damage more quickly.
For example:
• 85 dBA may cause permanent damage after ~8 hours
• 100 dBA may cause damage in ~15–30 minutes
Noise exposure limits therefore specify maximum allowable exposure time at given sound levels.
OSHA Noise Exposure Standards (United States)
The Occupational Safety and Health Administration (OSHA) sets legally enforceable noise exposure limits based on an 8-hour time-weighted average.
Key OSHA thresholds:
• 90 dBA – permissible exposure limit (PEL) for 8 hours
• 5 dBA exchange rate – every 5 dBA increase halves allowable exposure time
Hearing protection is required when workers exceed allowable limits.
OSHA emphasizes that perceived loudness is not a reliable indicator of hearing risk—measured sound pressure is what matters.
Canadian and European Noise Criteria
Canada
Most jurisdictions set an 8-hour exposure limit of 85 dBA, with exchange rates applied as sound levels increase. Federal regulations and some provinces use slightly different thresholds.
European Union
EU Directive 2003/10/EC establishes:
• Exposure limit value: 87 dBA (after hearing protection)
• Upper action value: 85 dBA
• Lower action value: 80 dBA
The directive prioritizes eliminating noise at the source and mandates worker training, monitoring, and health surveillance.
Health Effects of Noise Exposure
Hearing loss can be:
• Sensorineural – damage to inner ear or auditory nerve
• Conductive – blockage or damage in the outer or middle ear
• Mixed – combination of both
Excessive noise damages the microscopic hair cells in the cochlea. Once damaged, these cells do not regenerate.
Long-term or intense noise exposure can lead to:
• Permanent hearing loss
• Tinnitus (ringing in the ears)
• Stress and anxiety
• High blood pressure
• Fatigue and reduced concentration
Worker Rights and Employer Responsibilities
Workers have the right to:
• A workplace free from serious noise hazards
• Training and information about noise risks
• Access to exposure and monitoring records
• Protection from retaliation when reporting hazards
Employers are responsible for implementing hearing conservation programs when exposure thresholds are exceeded.
Penalties for Non-Compliance
Failure to comply with occupational noise standards can result in:
• Citations and fines
• Daily penalties for unresolved violations
• Increased workers’ compensation costs
• Legal liability in cases of injury or negligence
Penalties vary by jurisdiction but can be substantial, particularly for repeated or willful violations.
Strategies for Reducing Workplace Noise
Noise control is most effective when addressed at the source.
Common strategies include:
• Reducing compressed air velocity
• Adding exhaust mufflers
• Using engineered nozzles instead of open pipes
• Turning off air tools when not in use
• Maintaining equipment to prevent vibration and imbalance
A key principle:
Doubling the distance from a noise source reduces sound levels by approximately 6 dBA.
Additional controls include:
• Relocating noisy equipment
• Adding acoustic wall or ceiling treatments
• Installing barriers or enclosures
• Scheduling noisy tasks during low-occupancy shifts
When engineering and administrative controls are insufficient, hearing protection must be provided.
Why Noise Control Matters Beyond Compliance
Reducing noise exposure:
• Protects hearing and long-term health
• Improves communication and safety
• Reduces fatigue and error rates
• Lowers regulatory risk
• Improves overall working conditions
Noise is not just an inconvenience—it is a measurable occupational hazard.
Final Perspective
dBA is more than a technical unit—it is the language of human hearing risk. Understanding how sound is measured, how exposure accumulates, and how noise can be reduced allows facilities to make smarter design decisions and protect workers without sacrificing performance.
Noise control is not about silence.
It is about control, predictability, and responsibility.