Excessive workplace noise isn’t just an inconvenience — it’s a silent threat. From gradual hearing loss to stress and reduced concentration, loud environments can seriously affect both health and productivity.
But here’s the catch: not all noise is equal. Simply measuring decibels isn’t enough to understand real risk. That’s where A-weighted (dB(A)) and C-weighted (dB(C)) measurements come in.
These two “filters” help health & safety managers:
Accurately assess daily noise exposure vs. peak noise events
Stay compliant with UK noise regulations
Prevent long-term hearing damage and instant-impact injuries
If you manage workplace safety, understanding A vs C weighting isn’t optional — it’s essential for protecting workers and staying HSE-compliant.
In this guide, you’ll learn: ✅ The difference between A-weighted and C-weighted noise ✅ Legal noise limits under the Control of Noise at Work Regulations 2005 ✅ The best tools & techniques to measure noise exposure ✅ How to interpret and act on noise data to prevent harm
Let’s dig into the decibels — and make sure you’re measuring what really matters.
Measurement
Limit
Action Required
A-weighted Daily Exposure
80 dB(A) – Lower Exposure Action Value
Provide training and offer hearing protection.
A-weighted Daily Exposure
85 dB(A) – Upper Exposure Action Value
Reduce noise where possible and enforce hearing protection use.
A-weighted Daily Exposure
87 dB(A) – Exposure Limit Value
Legal maximum daily exposure, even with hearing protection.
C-weighted Peak Noise
140 dB(C) – Peak Sound Pressure
Legal maximum instantaneous noise level — never exceed.
2. What Are Weighted Averages in Noise Monitoring?
When you're monitoring noise in the workplace, it's easy to assume that a decibel is just a decibel. But our ears — and the law — don’t see it that way.
Weighted averages are adjustments made to sound measurements to better reflect how the human ear perceives sound. Some frequencies (like a screaming drill) are more harmful or irritating than others (like a distant low hum), even if the raw decibel levels are similar. That's where A-weighting and C-weighting come in.
Here's the key idea:
A-weighting (dB(A)) mimics how the human ear hears sound at moderate levels.
C-weighting (dB(C)) captures low-frequency and very loud sounds more accurately.
These "filters" help ensure that the numbers on your noise reports are meaningful — not just mathematical. They give you context. And in safety? Context is everything.
Understanding which weighting to use isn’t just technical nitpicking — it can make the difference between catching a hazard and missing it entirely.
Up next, we’ll compare A and C weighting side by side so you’ll know exactly which one to use — and when.
Tool
Best For
Key Advantage
Sound Level Meter (SLM)
Spot checks and walkaround assessments
Quick, easy way to identify noisy machinery or problem areas.
Noise Dosimeter
Monitoring worker exposure over an entire shift
Tracks daily or weekly exposure fluctuations in real time.
Smart Wearables (e.g., spacebands)
Continuous monitoring & real-time alerts
Detects peaks and assigns exposure to individuals or zones for proactive action.
3. A-Weighted vs. C-Weighted Sound Measurements
A-Weighted vs C-Weighted Noise: What’s the Difference?
A-weighting and C-weighting are two different ways to measure workplace noise — and they serve different purposes:
A-weighting (dB(A)) filters out very low and very high frequencies to mimic how the human ear hears sound over time. It’s used to assess daily or weekly noise exposure.
C-weighting (dB(C)) includes more low-frequency sound and measures peak sound pressure levels, making it essential for identifying sudden, loud noises that can cause instant hearing damage.
When Should You Use Each?
✅ Use A-weighting for long-term exposure, such as continuous machinery, motors, or HVAC systems. ✅ Use C-weighting for peak noise events, such as metal stamping, explosions, alarms, or impact tools. ✅ Measure both to get a complete picture of workplace noise risk — long-term hearing damage and immediate impact risks.
Weighting
What It Measures
Best For
Example Use
A-weighted (dB(A))
Filters out very low & high frequencies to reflect human hearing sensitivity over time.
Daily or weekly workplace noise exposure.
Factory machinery, fans, motors, HVAC systems.
C-weighted (dB(C))
Captures low-frequency and peak sound pressure levels accurately.
Sudden, loud impact or explosive noises.
Metal stamping, explosions, alarms, impact tools.
4. Regulatory Guidelines & Legal Limits
UK Workplace Noise Regulations
Workplace noise exposure is regulated under the Control of Noise at Work Regulations 2005. Employers must take action at specific noise thresholds to protect workers from hearing damage.
Daily Exposure Limits (A-weighted – dB(A))
80 dB(A) – Lower Exposure Action Value (LEAV): Provide information, training, and offer hearing protection.
85 dB(A) – Upper Exposure Action Value (UEAV): Take action to reduce noise levels and enforce hearing protection use.
87 dB(A) – Exposure Limit Value (ELV): The legal maximum daily exposure, even when hearing protection is worn.
These limits use A-weighting because they reflect how the human ear experiences noise over time.
Peak Noise Limits (C-weighted – dB(C))
140 dB(C): The maximum permitted peak sound level. Exceeding this — even for a split second — breaches UK law and risks instant hearing damage.
How to Stay Compliant
✅ Measure A-weighted noise for daily or weekly exposure. ✅ Measure C-weighted noise to detect dangerous peaks. ✅ Record and review data regularly, provide suitable hearing protection, and train staff on noise risks.
5. Tools & Techniques for Measuring Noise Exposure
Monitoring workplace noise isn’t just about owning the right equipment — it’s about knowing what to measure, when, and how. Here’s how to do it effectively:
1. Sound Level Meters (SLMs)
Best for quick spot checks and walkarounds.
Measure noise at a specific moment in time.
Can be set to show A-weighted or C-weighted levels — ideal for identifying noisy machinery or problem areas.
2. Noise Dosimeters
Worn by workers to track noise exposure throughout a shift.
Capture fluctuations in sound levels during real-world activity.
Crucial for checking if workers are exceeding daily or weekly legal limits.
3. Smart Wearables & Environmental Sensors
Devices like spacebands can monitor average noise levels and detect peak events in real time.
Assign exposure data to individuals or zones.
Provide instant alerts when thresholds are approached, allowing proactive action.
4. Calibration & Setup Tips
Always calibrate devices before use to ensure accuracy.
Record both A- and C-weighted readings if you need legal compliance.
When using dosimeters, place the microphone as close to the ear as possible.
By combining these tools, you’ll get a complete picture of noise risk — helping you act before exposure turns into harm.
6. How to Interpret Weighted Noise Data in the Real World
Collecting noise readings is only half the job — you need to know what they mean and how to act on them.
Scenario 1: Continuous Machinery Noise
Reading: Around 85 dB(A), no sudden peaks.
Action: This hits the Upper Exposure Action Value. Provide mandatory hearing protection and consider engineering controls (barriers, insulation).
Scenario 2: Sudden Impact Noise
Reading: Daily average only 78 dB(A), but a peak of 141 dB(C) recorded.
Action: You’ve breached the legal 140 dB(C) peak limit. Introduce noise-dampening measures, procedural changes, or re-schedule noisy activities.
Scenario 3: Low Average, Occasional Spikes
Reading: Normal level 65 dB(A), occasional spikes of 120 dB(C).
Action: Average exposure may be safe, but intermittent peaks still pose a risk. Use real-time alerts or adjust shift patterns to limit exposure.
Key Takeaways
A-weighted = Long-term exposure risk
C-weighted = Peak noise impact
Use both to guide PPE use, shift planning, and layout decisions.
7. The Risks of Getting It Wrong
Failing to measure noise exposure correctly can lead to hearing loss, legal fines, and serious compliance breaches. Here are common mistakes — and why they’re dangerous:
Risk: Spot checks during quiet periods give a false sense of safety.
Consequence: Workers remain exposed to unrecorded hazards.
3. Ignoring Individual Exposure
Risk: Static readings don’t track how workers move through noisy zones.
Consequence: Cumulative risks are overlooked, especially for mobile roles.
4. Not Acting on the Data
Risk: Even perfect readings are useless without action.
Consequence: Long-term hearing damage, repeat breaches, and legal liability.
✅ Bottom line: Real safety comes from real insight. Combine A- and C-weighted data, review it regularly, and act before exposure turns into harm.
8. Best Practices for H&S Managers
Strong noise monitoring isn’t just about ticking compliance boxes — it’s about preventing harm before it happens. Follow these best practices:
1. Calibrate Your Equipment Regularly
Ensure sound level meters and dosimeters are correctly calibrated to avoid inaccurate readings and compliance issues.
2. Use the Right Weighting for the Job
A-weighting: Long-term daily or weekly exposure.
C-weighting: Sudden peaks or high-impact noise events.
Always measure both for a complete risk profile.
3. Record & Review Data Over Time
Noise monitoring is ongoing. Track trends, identify problem areas, and act before exposure reaches action values.
4. Use Data to Train, Report & Validate
Educate workers on noise risks using real data.
Share reports with regulators and insurers to demonstrate compliance.
Use insights to plan better PPE use, shift patterns, or engineering controls.
✅ Proactive monitoring = safer teams + fewer compliance headaches.
9. Final Thoughts: Knowledge is Protection
Empowering Managers with Better Understanding = Safer Teams
When Health and Safety managers have a clear, well-rounded understanding of noise hazards and how to manage them, they become powerful advocates for a safer workplace. Knowledge transforms a manager from a compliance officer into a proactive protector—someone who’s not just checking boxes, but actively safeguarding team members from long-term health risks.
Good Noise Monitoring is a Proactive Compliance Tool, Not Just a Checkbox
Think of noise monitoring as an investment, not a task to tick off your list. When you embrace robust noise monitoring, you’re doing more than adhering to regulations—you’re fostering a culture of proactive safety. It’s not about being reactive when problems arise; it’s about spotting risks early and minimising exposure before it becomes a serious issue.
10. CTA / Next Steps
Try Our Noise Monitoring Tool
Ready to make your noise monitoring smarter? spacebands devices continuously monitor personal noise exposure using A-weighting for long-term assessment, while also detecting extreme noise events through threshold-based alerts—offering a practical approach to peak noise monitoring, even if not expressed in C-weighted decibels.
Download Our Free Toolbox Talk: "Understanding Noise Exposure at Work"
Get the conversation started on noise exposure with our free Toolbox Talk. This downloadable resource is a great way to engage your team in understanding the risks and protections around noise in the workplace. It’s designed to be quick, informative, and actionable.
Contact spacebands for a Demo on our HSE-Compliant Noise Assessment Tool
Don’t leave noise management to chance. Reach out to spacebands for a demo of our noise assessment tool that’s fully compliant with HSE standards. Protect your workforce with data-driven insights and proactive noise monitoring that makes a difference.
FAQ Section
1. What is the difference between A-weighting and C-weighting in noise monitoring?
A-weighting (dB(A)) mimics how the human ear hears sound at moderate levels, focusing on mid-range frequencies. C-weighting (dB(C)) captures more low-frequency and high-energy sounds, making it ideal for measuring sudden, loud noise events like bangs, booms, and impacts.
2. When should I use A-weighted vs. C-weighted noise measurements?
Use A-weighting for assessing daily or weekly exposure, as it reflects how we perceive long-term noise risk. Use C-weighting for peak noise events, where sudden loud sounds can cause instant hearing damage — even if average exposure is low.
3. What are the UK legal limits for workplace noise exposure?
Under the Control of Noise at Work Regulations 2005:
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