Airborne sound · documented RMS quantity · reference 20 µPa

RMS Sound-Pressure Level Converter

Convert a documented unweighted RMS sound pressure in air to or from its logarithmic level relative to 20 µPa.

p is RMS, not peakReference stated explicitlyNo hearing or safety verdict

Quantity conversion only—not a sound-level-meter, dose, exposure or hearing-risk calculation. The result is valid only when the entered pressure is the RMS/effective acoustic pressure for the documented time interval and frequency band, or when the entered level uses the same 20 µPa reference and unweighted RMS definition. It is not static pressure, instantaneous/peak pressure, sound power, sound intensity or underwater level.

Documented quantity

Conversion direction

Input value

Measurement / calculation record ID

Medium and measurement environment

RMS averaging interval / time processing

Frequency band / bandwidth

Frequency weighting / filter record

Instrument / processing system and mode

Calibration / traceability and uncertainty

Definition source, edition, clause and reference

Prepared / reviewed by

Record date

Notes and exclusions Optional: field type, microphone orientation, background correction, tonal/impulsive character, processing chain

The quantity is airborne acoustic pressure and uses p₀ = 20 µPa; it is not an underwater level (commonly stated with a different reference), static pressure, sound power or sound intensity.
The pressure is RMS/effective over the recorded time and frequency processing, or the level is defined from that same quantity. It is not peak, peak-to-peak or instantaneous pressure.
The input is unweighted. A-, C-, Z- or band-weighted levels require a matching processed-pressure definition and must not be interpreted as unweighted broadband pressure.
No threshold-of-hearing, loudness, pain, dose, exposure-limit, hearing-protection or compliance decision will be inferred from this arithmetic result.

Converted quantity

Sound-pressure level Lp

—

RMS sound pressure p

—

Reference pressure p0

20 µPa = 2 × 10⁻⁵ Pa

Equations, units and classification

L_p = 20 lg(p / p₀) dB
p = p₀ × 10^{Lp / 20}
p₀ = 20 µPa = 2 × 10⁻⁵ Pa

Here p is the RMS/effective sound pressure after the documented time and frequency processing, and p₀ is the reference pressure. The inverse follows algebraically. This page classifies the relation as a general logarithmic level definition independently supported by public NIST material; the public ISO card confirms the current acoustics-quantities standard and amendment but does not expose its licensed table or exact clause wording.

Model boundary and corrected claims

Reference is not an individual hearing threshold. 20 µPa is the stated reference quantity. Human audibility depends on frequency, person, signal, duration and conditions; 0 dB re 20 µPa is not universal silence or “the quietest sound most people detect.”
No pain or sound-source table. Former conversation, pain-threshold and jet-engine examples mixed context-dependent perception/source descriptions with pure pressure ratios and were not required for the conversion.
Weighted level is not unweighted pressure. A-weighting is frequency processing. A single A-weighted level can be mapped to a corresponding A-weighted effective pressure magnitude when the same definition/reference is used, but it cannot reconstruct the unweighted spectrum or broadband RMS pressure. This worksheet intentionally requires unweighted input.
No 94 dB = 1 Pa identity. With p₀ = 20 µPa, exactly 1 Pa gives about 93.9794 dB, and exactly 94 dB gives about 1.00237 Pa. “94 dB ≈ 1 Pa” is only a rounded reference example.
No measurement or compliance inference. IEC 61672-1:2013 specifies performance for time-weighting, integrating-averaging and integrating sound level meters, including class 1/class 2 and uncertainty requirements. This webpage does not implement an instrument, weighting filter or conformity test.
Strict numerical domain. Pressure must be finite and greater than zero; both directions reject malformed/partial input, underflow to zero, overflow and nonfinite output. Negative finite levels are valid ratios.

Source traceability

Claim	Klassifikation	Evidence
ISO 80000-8:2020 Edition 2 gives names, symbols, definitions and units for acoustics quantities; it remains current after confirmation in 2025 and has Amendment 1:2025.	Official ISO public status/scope	ISO 80000-8:2020 og Amd 1:2025; exact normative content remains licensed
Lp = 20 lg(p/p0) dB and p0 = 20 µPa; reference must be stated.	Official public metrology guidance	NIST SP 811, Chapter 8
For acoustical measurement, p is temporal RMS sound pressure over an appropriate averaging period and p0 = 20 µPa.	Official public NBS/NIST technical report	NBSIR 75-938, §2.1.1
IEC 61672-1:2013 Edition 2 covers time-weighting, integrating-averaging and integrating sound level meters, class 1/class 2 and measurement uncertainty; stability date 2029.	Official IEC public status/scope	IEC 61672-1:2013

Accessed: 15 July 2026. Public sources support the displayed general relation, RMS meaning, reference and instrument boundary. Exact ISO/IEC clauses and any conformance decision remain NEEDS_LICENSED_SOURCE.

Arithmetic reference examples

For L_p = 94 dB re 20 µPa, p = 20 × 10⁻⁶ × 10^94/20 ≈ 1.00237447 Pa RMS. For p = 1 Pa RMS, L_p = 20 lg(1 / 20 × 10⁻⁶) ≈ 93.9794001 dB. These are quantity conversions, not loudness or safety statements.

Questions

Can I enter a negative level?

Yes. A negative dB value means the RMS pressure is below the stated 20 µPa reference; it does not mean negative physical pressure magnitude.

Can I enter dB(A)?

Not in this unweighted worksheet. The same logarithmic ratio may describe a processed A-weighted effective pressure, but that result is not the unweighted broadband RMS pressure and cannot recover the spectrum.

Why require an averaging interval and band?

RMS pressure depends on the signal interval and frequency processing. Without those records, the number is not sufficiently defined for comparison or traceability.