Unit Converters
Sound Level and Intensity Ratio Calculator
Relate sound level, intensity ratio, reference intensity, distance attenuation, barrier reduction, and duration in one transparent calculation. The distance term follows ideal spherical spreading, while the barrier term remains a separate entered allowance that must be supported by the real geometry and frequency spectrum.
Level difference-
Intensity ratio to reference-
Source intensity from entered reference-
Point-source distance attenuation-
Level after distance and barrier attenuation-
Adjusted intensity ratio to reference-
Level-duration energy reference-
Second distance divided by first-
Decision view
Distance-and-barrier attenuation curve
Distance-and-barrier attenuation curveThe source level follows ideal point-source distance decay, while the entered barrier loss is shown as a separate lower curve and far-point marker.
Exact scenario comparisonSecond distance from point source (m) changes while all other entered assumptions remain constant.
| Second distance from point source (m) | Level difference | Intensity ratio to reference | Source intensity from entered reference | Point-source distance attenuation | Level after distance and barrier attenuation | Adjusted intensity ratio to reference | Level-duration energy reference | Second distance divided by first |
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How to use Sound Level and Intensity Ratio Calculator
- Enter source and comparison levels using the same weighting, averaging period, and measurement convention.
- Enter positive source and receiver distances measured consistently from the same acoustic source.
- Use barrier attenuation only when it is supported by geometry or measurement; evaluate hearing exposure with an applicable occupational standard separately.
Calculator guide
Understanding Sound Level and Intensity Ratio Calculator
A decibel is a logarithmic ratio, not a linear sound quantity. This calculator converts a level difference to an intensity ratio, estimates free-field point-source loss between two distances, subtracts a stated barrier attenuation, and reports the resulting level without presenting it as a hearing-risk assessment.
Detailed calculation process
Relate decibel level, intensity, and distance loss
The default uses an 85 dB source, a 70 dB comparison level, I₀ = 10⁻¹² W/m², distances of 1 m and 4 m, 8 dB barrier attenuation, and a 2-hour duration.
General formula: ΔL = L_s - L_refq = 10^(ΔL/10)I_s = I₀ × 10^(L_s/10)A_d = 20 × log10(d₂/d₁)L₂ = L_s - A_d - A_bq₂ = 10^((L₂ - L_ref)/10)E_rel = 10^(L₂/10) × h Level differences use a power ratio with divisor ten. Absolute intensity uses the chosen reference intensity. Ideal point-source spreading uses twenty times the distance-ratio logarithm, after which the separately entered barrier loss is subtracted.
What each symbol means
Worked substitution with the default inputs
Under the stated ideal assumptions, the receiver level is 64.9588 dB. Field measurements or a validated acoustic model should replace the estimate whenever reflections, directivity, barriers, or compliance decisions matter.
Purpose-built visual
Distance-and-barrier attenuation curve
The live curve shows ideal distance decay, marks the entered near and far points, and separates the barrier reduction from geometric spreading.
Worked situations
Practical examples
- An 85 dB source is 15 dB above a 70 dB reference, so its intensity ratio is 10^(15/10) = 31.6228.
- Moving from 1 m to 4 m in an ideal free field gives 20 log10(4/1) = 12.0412 dB of geometric attenuation.
- With an additional 8 dB barrier allowance, the default receiver level is 85 - 12.0412 - 8 = 64.9588 dB.
Better inputs
Useful tips
- Treat decibels as logarithmic values; do not add or average dB readings with ordinary arithmetic.
- Match weighting and time response, such as dBA slow or dBC peak, before comparing two measurements.
- Keep source distance and background noise consistent because both can materially change the reported level.
Before relying on the result
Limitations and common mistakes
- The inverse-distance model assumes a point source in a free field; reflections, directivity, near-field behaviour, weather, ground effects, and multiple sources can dominate real measurements.
- Barrier attenuation varies strongly with frequency, geometry, absorption, leakage, diffraction, and receiver position; one entered dB value is only a scenario assumption.
- The duration output is a relative exposure indicator, not an OSHA, NIOSH, EU, or other regulatory noise dose calculation.
Reference
Key terms
- Decibel
- A logarithmic level unit expressing a ratio rather than a linear sound quantity.
- Reference intensity
- The intensity I₀ used to convert a sound level into watts per square metre.
- Geometric spreading
- Level reduction caused by sound energy spreading over a larger area with distance.
- Barrier attenuation
- Entered level reduction attributed to an obstacle or enclosure, stated in decibels.
Important note
Do not use the modeled receiver level as a hearing-protection or compliance decision by itself. Confirm source directivity, frequency spectrum, reflections, barrier performance, weighting, instrument calibration, and the applicable exposure standard.
Frequently asked questions
Does twice the decibel value mean twice the sound intensity?
No. Decibels are logarithmic; a 3 dB increase is about twice the intensity, while 10 dB is ten times.
Why does doubling distance reduce about 6 dB?
For an ideal point source, 20 log10(2) is approximately 6.02 dB.
Can I add two sound sources by adding their dB values?
No. Convert each level to linear intensity, add the intensities, and convert the sum back to decibels.
Is the adjusted level safe for a two-hour exposure?
This page does not determine safety. Apply the relevant exposure standard and verify the actual weighted, time-averaged measurement.