Sound Level Converter
Sound is a pressure wave propagating through a medium, and sound levels are typically expressed in decibels (dB) relative to a reference pressure. Sound pressure level (dB SPL) uses a reference pressure of 20 microPascals (20 μPa), the approximate threshold of human hearing at 1,000 Hz. The decibel scale is logarithmic: a 10 dB increase corresponds to a tenfold increase in pressure, and a 20 dB increase to a hundredfold increase. This logarithmic relationship roughly matches human auditory perception, which is why our ears respond to ratios of sound intensity rather than absolute changes. Converting between decibel values and pressure measurements in pascals is essential in acoustics, occupational safety (hearing protection and noise limits), audio engineering, and environmental noise assessment. The formula is straightforward: dB SPL = 20 * log10(P / 0.00002), where P is pressure in pascals. This calculator converts between dB SPL and pascals, and includes a reference table of common everyday sounds on the dB scale. Type a value into either field and the other updates instantly.
Sound pressure level reference table
Examples of common sounds on the dB SPL scale (reference: 20 μPa):
| Sound | dB SPL |
|---|---|
| Threshold of hearing | 0 |
| Whisper, quiet library | 20-30 |
| Normal conversation | 60 |
| Busy traffic, vacuum cleaner | 70-85 |
| Concert, lawn mower | 110 |
| Jet engine at takeoff | 140 |
Sound level conversion formula
The relationship between sound pressure and decibels is defined as:
dB SPL = 20 log10(P / 0.00002)
P (Pa) = 0.00002 × 10(dB/20)
where P is the root-mean-square (RMS) sound pressure in pascals and 0.00002 Pa is the reference pressure (threshold of human hearing). All dB values are referenced to this standard.
Sound level converter: frequently asked questions
What is a decibel (dB)?
A decibel (dB) is a logarithmic unit used to express the ratio of a physical quantity to a reference value. For sound pressure level (dB SPL), the reference pressure is 20 microPascals (20 μPa), the approximate threshold of human hearing at 1 kHz. Because the decibel scale is logarithmic, a 10 dB increase represents a tenfold increase in sound pressure, and a 20 dB increase represents a hundredfold increase.
What is the formula for dB SPL?
The formula is: dB SPL = 20 * log10(P / 0.00002), where P is the sound pressure in pascals and 0.00002 Pa is the reference pressure. Conversely, P = 0.00002 * 10^(dB/20). This logarithmic relationship means the decibel scale compresses large pressure ranges into manageable numbers.
Why is the decibel scale logarithmic?
Human hearing sensitivity roughly follows a logarithmic scale: we perceive equal ratios of pressure as equal differences in loudness. A doubling of sound pressure (a 6 dB increase) is perceived as roughly a perceptible increase in loudness across most of the hearing range. The logarithmic scale reflects this psychoacoustic reality.
Is 0 dB silent?
Zero dB (0 dB SPL) is not silence; it represents the reference threshold of human hearing at 20 microPascals. Sounds quieter than this are below the average human hearing threshold. Negative dB values (like -10 dB) represent pressures below the reference, inaudible to most people under normal conditions.
What is the difference between dB SPL and other decibel scales?
dB SPL (Sound Pressure Level) is referenced to 20 μPa. dB SIL (Sound Intensity Level) is referenced to 10^-12 W/m2. dB PWL (Sound Power Level) is referenced to 10^-12 W. Different contexts use different reference levels. This calculator uses dB SPL, the most common in acoustics and occupational safety.
Official sources
- ISO 80000-8:2007: Quantities and units; Acoustics.
- ANSI S1.1-2013: Acoustical Terminology.
- OSHA 29 CFR 1910.95: Occupational Noise Exposure.
Reviewed by the CalculatorHub team, edited by James Graham, 14 June 2026. See our methodology.