Noise Levels and Decibels: How to Read Any Figure You Meet
Decibel charts are everywhere and sources are rare. This guide teaches you to interrogate a figure instead of trusting it, and shows where real documentation exists.
Reviewed by our team against authoritative public-health sources. See our editorial standards.
Quick Answer
A decibel figure only means something once you know four things: which quantity it is (sound pressure or sound power), at what distance it was measured, with what frequency and time weighting, and under what conditions. Most published charts state none of these, which is why the same sound appears with wildly different numbers across sites. This guide explains each of the four questions, shows where genuinely documented figures come from — regulatory declarations, type-approval limits, occupational dosimetry, peer-reviewed measurement — and links to the pages on this site where a specific sound's evidence is set out with its own sources.
We deliberately no longer publish a generic chart of everyday sound levels here. The rows in such charts are almost never traceable, and replacing them with our own guesses would repeat the problem.
Prolonged exposure above 85 dB can damage hearing.
The four questions that make a figure meaningful
Any time you meet a decibel number, these four questions decide whether it is usable. If a source cannot answer them, the figure is decoration.
| Question | Why it matters | Typical failure |
|---|---|---|
| Which quantity? | Sound power describes a machine; sound pressure describes a place. They are different physical quantities. | An appliance label's dB(A) re 1 pW presented as what you hear in the room |
| At what distance? | Level falls with distance, so a figure without a distance is not a measurement. | "A chainsaw is 110 dB" with no position stated |
| With what weighting? | A, C and Z weighting, and fast, slow or peak time weighting, give different numbers for the same sound. | A peak value quoted as if it were an average |
| Under what conditions? | Programme, load, surface, room and duty cycle can change a result by tens of decibels. | A laboratory eco-cycle figure applied to a real kitchen |
These four questions are the editorial standard for every evidence page on this site. Where a source cannot answer one, we mark it as not stated rather than filling it in.
Sound power against sound pressure
Sound power is the total acoustic energy a source radiates. It is a property of the machine, independent of distance and room, and it is what appliance energy labels and outdoor-machinery directives declare, in dB(A) re 1 pW.
Sound pressure is what a meter reads at a point and what your ears respond to. It depends on distance, room surfaces and position, and it is referenced to 20 micropascals.
No general conversion between them exists without a defined measurement environment. This single confusion produces more wrong numbers online than any other.
Where documented figures actually come from
Real sources fall into a few families, and knowing which family a number belongs to tells you what it can be used for.
| Family | Example | What it can tell you |
|---|---|---|
| Regulatory declaration | EU energy label sound power for a dishwasher or washing machine | How models compare, in a laboratory metric |
| Type-approval limit | UN Regulation 28 requirements for vehicle horns | What a device is allowed or required to produce in a defined test |
| Occupational exposure criterion | OSHA Table G-16, the NIOSH recommended exposure limit | What assessed workplace exposure is permitted or recommended |
| Occupational dosimetry study | NIOSH kennel-noise health hazard evaluations | What workers in a specific setting actually accumulated |
| Peer-reviewed measurement | Dental handpiece levels measured 30 cm from the clinician's ear | A level under stated conditions at a stated position |
Each family answers a different question. None of them is a general-purpose "how loud is X" figure, which is why our pages state the family alongside the number.
Level, duration and the exposure frameworks
Exposure is not level. Every published framework combines a level, an averaging period and an exchange rate that trades one against the other: OSHA enforces 90 dBA over eight hours with a 5 dB exchange rate, NIOSH recommends 85 dBA over eight hours with a 3 dB rate, and the EU sets an 87 dB(A) daily limit value with action values at 80 and 85 dB(A).
All three are occupational, all three describe assessed exposure rather than individual sounds, and none of them identifies a level at which hearing damage begins. We set out how they are built, and we do not turn them into personal allowances.
What measurement on a phone can and cannot do
A phone microphone is uncalibrated, has an unknown frequency response, and sits inside an audio path that may apply processing you cannot fully defeat. It cannot meet the instrument standards that environmental and occupational measurement assume.
Uncalibrated, our meter is explicit about this: it reports an A-weighted digital signal level in dBFS, which is relative rather than sound pressure. A one-time local calibration against a known reference produces an estimated dBA figure, labelled as an estimate.
Within those limits, measurement is genuinely useful — for comparing two rooms, two settings, two positions, or before and after a change. That is a different job from certifying a level, and it is the job the tool is built for.
Where the documented figures live on this site
Rather than a chart, this site publishes evidence pages. Each one states what was measured, by whom, at what distance, in which metric, and what the source does not establish.
For appliance declarations, start with the dishwasher and washing-machine pages, which explain the EU label metric in detail. For exposure frameworks, the 85 decibels page and the daily exposure page set out the criteria and who owns them. For measurement method, the outdoor measurement page covers the standards, and the decibel mathematics page covers why the scale behaves as it does. For a sound where the honest answer is that no figure is defensible, the thunder and dog-bark pages show what that looks like written out.
Hearing Safety
Noise-induced hearing loss is permanent and cumulative. There is no medical treatment that can restore hearing damaged by noise exposure. Prevention through awareness and hearing protection is the only effective strategy. If you need to raise your voice to be heard by someone 1 meter away, the noise level likely exceeds 85 dB and hearing protection should be used.
Frequently Asked Questions
Why did you remove the decibel chart?
Because its rows had no traceable sources. A chart of unsourced numbers looks authoritative and is not, so we replaced it with an explanation of how to read a figure and links to pages where the evidence is documented.
What is the difference between sound power and sound pressure?
Sound power is the total energy a source radiates and is a property of the machine. Sound pressure is what a meter reads at a point, and it depends on distance and room. There is no general conversion between them.
What does A-weighting do?
It applies a frequency-dependent filter approximating human hearing's uneven sensitivity, so that a single number better reflects perception. C and Z weighting are used for other purposes, particularly peaks.
Which exposure limit should I use?
It depends on jurisdiction and purpose. OSHA's is enforceable in covered US workplaces, NIOSH's is a health-based recommendation, and the EU directive applies in EU workplaces. None of them applies to household or leisure noise as law.
Can I trust any figure I find online?
Ask the four questions. If a page cannot say which quantity, what distance, what weighting and under what conditions, treat the number as unsupported.
Explore More
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6 min readEvidence behind the levels on this page
Every sound level quoted above comes from one of the publications below. For each one we record what was actually measured, the microphone position or distance where that is stated, the metric used, and what the figure can and cannot tell you. Where a source did not state a condition, we say so rather than filling the gap.
29 CFR 1910.95, occupational noise exposure, including Table G-16
US Occupational Safety and Health Administration · US federal regulation
- What was measured
- Permissible occupational exposures and impulsive noise ceiling
- Reported level
- 90 dBA eight-hour TWA, 5 dB exchange rate; impulsive noise not above 140 dB peak
- Distance / position
- At the worker
- Frequency weighting
- A-weighted, slow response
- Conditions
- Assessed exposure in covered US workplaces
- Supports on this page
- The exposure-framework section of this guide
- Limitations
- Occupational scope; not a description of individual sound sources.
European Commission · 2019 · EU regulation
- What was measured
- Declared airborne acoustical noise emission and noise class bands
- Reported level
- Declared in dB(A) re 1 pW, with class bands defined per product group
- Distance / position
- Not applicable — sound power is independent of distance
- Frequency weighting
- A-weighted sound power
- Conditions
- Defined test programmes under EU labelling law
- Supports on this page
- The sound power against sound pressure section and the regulatory-declaration family
- Limitations
- Declares emission for comparison between models; it does not describe the level in a room.
ISO 80000-3 level definitions and the IEC 61672 sound level meter series
International Organization for Standardization / IEC · International standards
- What was measured
- Definition of decibel levels, and instrument performance classes for sound level meters
- Reported level
- 10 · log₁₀ for power quantities and 20 · log₁₀ for field quantities; class 1 and class 2 instrument specifications
- Distance / position
- Not applicable
- Frequency weighting
- Defines A, C and Z frequency weightings and fast, slow and peak time weightings
- Conditions
- Definitional and instrument specification
- Supports on this page
- The four-questions framework and the phone-measurement limits
- Limitations
- Paid standards; we quote scope and definitional content rather than numeric tolerance clauses we could not verify from the full texts.
Levels on this page are published measurements, quoted with the position and conditions their source states. See our editorial standards for how we source and review noise data.
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