Decibels don’t work like regular numbers and that can confuse even experienced managers.
When working with businesses across NSW interpreting noise data and manage hearing risks, one common point of confusion I hear is:
“Why don’t the average decibel readings add up the way I expect them to?”
That confusion is completely valid. It’s not your maths, it’s how sound works. Let’s clear it up.
Understanding the Decibel Scale: Logarithmic, Not Linear
Unlike temperature or weight, decibels (dB) operate on a logarithmic scale. This means:
You can’t add or average dB values the way you would other numbers
A few high readings can disproportionately raise the overall result
Louder sounds carry exponentially more energy
What that means in practice:
88 dB(A) has twice the energy of 85 dB(A)
91 dB(A) has four times the energy of 85 dB(A)
So if one machine records 91 dB(A) and another records 87 dB(A), the overall exposure (LAeq) isn’t simply 89 dB. It’s closer to 90.5 dB(A) because the louder source dominates.
According to the Safe Work Australia Code of Practice: Managing Noise and Preventing Hearing Loss at Work, understanding how noise energy builds up is essential for effective control and compliance.
Question: Why can’t you simply average decibel readings?
Answer:
You can’t average decibel readings directly because they use a logarithmic scale. Instead, exposure is based on sound energy, so louder noises have a much greater impact on the overall result.
A Common Myth to Watch Out For
Many believe that short bursts of high noise aren’t a problem if the average seems acceptable. In reality, these spikes can significantly impact total exposure and increase risk even if they’re brief.
Why This Matters for Workplace Noise Assessments
When reviewing noise data from a consultant, remember:
- It’s not just about individual readings, it’s about energy exposure over time
- Short bursts of high noise can dramatically affect overall exposure
- The combined LAeq reflects the true workplace risk, not a simple average
This is especially critical when you’re assessing:
High-speed processing equipment
Irregular loud bursts (e.g., compressed air, grinders)
Machinery with inconsistent but high peak outputs
If you’d like to learn more about noise compliance basics before diving into data, check out our related article: How Loud Is Too Loud? A Practical Guide to Workplace Noise Compliance.
Decoding the Results
A client in regional NSW had machine readings from 84 to 93 dB(A). On paper, the “average” seemed safe. But the LAeq showed exposure closer to 91 dB(A) because one high-noise process was running continuously. That result triggered a need for hearing protection and an updated noise management plan.
Once the team understood why the number was higher than expected, they could confidently explain it to staff and auditors and then take the right actions.
Why Explaining This to Your Team Matters
Workers may push back on wearing hearing protection if the environment “doesn’t feel that loud.”
But when you explain that:
Sound energy doubles every 3 dB
A few noisy tasks can make a big impact
We measure energy, not just volume
… they’re far more likely to take it seriously and support the controls.
Want Help Interpreting Your Noise Report?
We help small and medium businesses understand what the numbers mean, what’s required by law, and how to implement practical, realistic solutions, without confusion or overkill.
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ABOUT THE Author - Kylie Dowell
Kylie Dowell is a seasoned WHS consultant, trainer, and safety advocate with over 25 years of experience helping Australian businesses create safer, compliant workplaces.
Through her partnership with TEAMS, an accredited Registered Training Organisation, Kylie delivers a wide range of training up to Advanced Diploma level, empowering businesses with the knowledge and skills to manage safety effectively.
As an approved trainer for Health and Safety Representative (HSR) courses by three Safety Regulators, Kylie has guided countless organisations in building stronger safety cultures and fostering healthier work environments.
Specialising in practical and effective safety solutions, she works closely with small and medium-sized businesses to simplify complex WHS requirements, making safety approachable and achievable.
When she’s not delivering high-quality training or conducting ISO 45001-certified audits, Kylie enjoys collaborating with her clients to design tailored workshops and strategies that suit their unique needs.
Ready to make safety simpler? Get in touch with Kylie today for personalised support.