What this calculator works out
This calculator combines several equally loud noise sources into a single decibel figure, with an optional adjustment.
Decibels do not add arithmetically. Two identical sources are not twice as loud in decibel terms — they are 3 dB higher, which is a much smaller change than the doubling suggests.
Enter your details
Before you interpret the figure
- The calculation assumes every source is the same level. Where one source dominates, the total is close to that source alone.
- Decibel figures are meaningless without knowing where they were measured. Sound falls off with distance.
- The adjustment allows for room acoustics, distance or a correction from a measured reading.
- This estimates sound level, not nuisance. Whether noise is a problem depends on time of day, duration and character as much as level.
Two equal sources add 3 dB, four add 6 dB, ten add 10 dB. The logarithmic scale means a source 10 dB below another contributes almost nothing to the total. It also means that silencing the loudest source is far more effective than reducing several quiet ones.
How this calculator works
Logarithmic addition of equal sources:
Total dB = level per source + 10 × log₁₀(number of sources) + adjustmentThe 10 log₁₀ term is what makes decibels add logarithmically. It gives +3 dB for two sources, +4.8 for three, +6 for four and +10 for ten.
Where sources differ in level, this simplification overstates the total. The correct method converts each to sound intensity, sums them and converts back — for practical purposes, a source 10 dB below the loudest can be ignored.
Worked example: three sources at 70 dB
Using the default figures — 70 dB per source, 3 sources, no adjustment:
- Total: 74.77 dB
Three sources at 70 dB give under 75 dB, not 210. Tripling the noise sources adds under 5 dB, which is a noticeable but modest increase — roughly the difference between a normal conversation and a slightly raised one. This is why turning off two of three appliances helps less than expected, and why removing the single loudest source helps far more.
Common mistakes
- Adding decibels arithmetically. They are logarithmic; 70 + 70 is 73, not 140.
- Applying it to sources of different levels. The result overstates the total.
- Quoting a level without a distance. Sound falls off as you move away.
- Treating level as the whole of nuisance. Timing, duration and character matter as much.
- Using a phone app as a measurement. They are indicative, not calibrated.
Frequently asked questions
What decibel levels are typical?
Roughly: a quiet room 30 dB, normal conversation 60, a vacuum cleaner or busy road 70 to 80, a lawnmower or food blender 85 to 95, a chainsaw or nightclub above 100. Hearing damage risk relates to both level and exposure time — around 85 dB is the level at which workplace hearing protection duties begin.
What can I do about a noisy neighbour?
Speak to them first, since a great deal of noise is unintentional and easily fixed. If that fails, local authorities have a statutory duty to investigate noise amounting to a statutory nuisance and can serve an abatement notice. Keeping a diary of dates, times and duration is what an investigation will ask for. Mediation services exist and are often more effective than enforcement.
What counts as a statutory nuisance?
Noise that unreasonably interferes with the use or enjoyment of a home, judged on level, duration, frequency, time of day and the character of the area. There is no fixed decibel threshold, and there is no general law against noise at particular hours — the common belief in an 11pm cut-off is not accurate, though time of day is a factor in the assessment.
How do I reduce noise in my own home?
Deal with the loudest source first, since the logarithm means everything else contributes little. Beyond that: soft furnishings absorb reflected sound, heavy curtains and draught-proofing reduce transmission through windows and gaps, and anti-vibration mats reduce noise carried through the structure by appliances.
Is what I enter stored?
No. Figures are processed in your browser and never transmitted or retained.
Related tools
References
- GOV.UK — statutory noise nuisance, neighbour disputes and local authority powers
- Health and Safety Executive — noise exposure limits and hearing protection
Sources are checked at publication and can change — how I choose and check references.