Measure loudness precisely with flexible acoustic input options. Convert units and compare scenarios quickly today. Download clean reports to share, archive, and audit later.
Use consistent reference values when comparing measurements. In air, SPL commonly uses p₀ = 20 µPa.
| Scenario | Inputs | Key output |
|---|---|---|
| Pressure method | p = 0.2 Pa, p₀ = 20 µPa | Lp ≈ 80 dB |
| Intensity method | I = 0.001 W/m², I₀ = 1e−12 W/m² | LI = 90 dB |
| Power & distance | Lw = 90 dB, r = 2 m, Q = 1 | Lp ≈ 73 dB |
| Inverse method | Lp = 80 dB, p₀ = 20 µPa | p ≈ 0.2 Pa |
Sound pressure level (SPL) expresses the strength of a sound field using a logarithmic scale. The value is based on RMS acoustic pressure, which is the time‑averaged pressure fluctuation around ambient air pressure. Engineers use SPL to compare sources, quantify exposure, and track changes after treatments such as barriers or absorbers.
Acoustic pressures span many orders of magnitude, so the decibel scale compresses wide ranges into practical numbers. A 20 dB increase corresponds to a tenfold increase in pressure amplitude, while 10 dB corresponds to tenfold intensity. This calculator lets you keep references explicit, so your results remain comparable across studies.
In air, a common reference is p0 = 20 µPa, roughly the threshold of hearing near 1 kHz. In water or special standards, different references are used. Always report the reference with the level, especially when sharing results between labs.
If you have microphone data as RMS pressure, SPL follows Lp = 20 log10(p/p0). For example, p = 0.2 Pa in air gives about 80 dB re 20 µPa. Use the unit converter when readings are provided in kPa, µPa, or psi equivalents.
When intensity I is known, an intensity level can be computed with 10 log10(I/I0). In a plane wave, I ≈ p²/(ρc), linking intensity to pressure through medium density and sound speed. This option is useful for comparing power flow through ducts, panels, or measurement grids.
If sound power level Lw and distance are available, free‑field models estimate SPL by accounting for spherical spreading. Doubling distance ideally reduces level by about 6 dB in a free field. Real environments add reflections, directivity, and absorption, so treat this as a first‑order estimate.
Quiet libraries can be ~30–40 dB, normal conversation ~60 dB, busy traffic ~70–85 dB, and some power tools exceed 100 dB. For occupational planning, small changes matter: 3 dB represents roughly a doubling of acoustic energy. Use the calculator to quantify before‑and‑after changes in controls.
Calibrate microphones, note weighting (A/C/Z) and time averaging, and avoid wind or handling noise. Measure at representative positions and document distance, environment, and background levels. Consistent settings make trends and comparisons far more reliable.
SPL describes sound at a location. Sound power describes total source emission. SPL depends on distance, environment, and direction, while sound power is a source property.
Sound intensity is proportional to pressure squared. Converting a squared relationship to decibels introduces the factor 20 rather than 10 for pressure ratios.
For air acoustics, 20 µPa is widely used. For underwater acoustics, 1 µPa is common. Use the reference required by your standard and report it with results.
SPL is a physical metric. Perceived loudness depends on frequency content, duration, and weighting. A‑weighting often aligns better with hearing sensitivity than unweighted levels.
Only in ideal free‑field conditions for a point source. Reflections, directivity, ground effects, and atmospheric absorption can reduce or increase the change from the 6 dB rule.
Yes. With intensity and a reference intensity, you can compute an intensity level. With medium properties (ρ and c), you can also estimate equivalent pressure using plane‑wave relations.
A 3 dB increase is about a doubling of acoustic energy. It may be barely noticeable for some signals, but it is important for exposure and engineering comparisons.
Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.