Sound Level Converter

Sound-level units can describe different sides of the same acoustic problem. Decibels are logarithmic ratios used in measurement and regulation. Phons are a loudness-level unit tied to human hearing. Sones are a linearized loudness scale where doubling sones represents roughly doubling perceived loudness under the model. This converter moves among decibel (dB), phon, and sone using the assumptions in the calculator.

The most important assumption is displayed in the result note: dB-to-phon conversion assumes a 1 kHz tone. At that frequency, the calculator treats dB and phon as numerically equal. Real hearing is frequency dependent; a low bass tone and a midrange tone can have the same measured sound pressure level but different perceived loudness. This page is therefore a unit and loudness-model converter, not a calibrated sound meter, audiology test, or occupational exposure assessment.

What the calculation gives

the calculator asks for Value, From unit, and To unit. The value must be nonnegative, and if the source unit is sone it must be greater than zero. The allowed units are decibel, phon, and sone. The primary result is formatted with one decimal place, and the result list shows all three supported units after the same conversion.

Under the stated 1 kHz simplification, dB to phon is equal and phon to dB is equal, phon to sone uses a power of two, and sone to phon uses a base-two logarithm. That means sone is the only supported unit with a strict positive input requirement. If you need exposure duration rather than unit conversion, see the noise exposure calculator. For decibel math such as combining sources, use the decibel calculator rather than adding readings manually.

Formula

For the 1 kHz assumption:

$\text{phon} = \text{dB}$

To convert phon to sone:

$\text{sone} = 2^{\frac{\text{phon} - 40}{10}}$

To convert sone back to phon:

$\text{phon} = 40 + 10\ \log_{2}\left(\text{sone}\right)$

The dB output then equals the phon value under this same simplified model.

Worked example matching the default

The default input is 60 dB, converting from decibel to phon. Because the calculator treats dB and phon as equal at 1 kHz, the primary result is:

$\text{phon} = 60\ \text{phon}$

The result list also calculates sones from the same phon value:

$\text{sone} = 2^{\frac{60 - 40}{10}} = 2^{2} = 4\ \text{sones}$

The displayed list therefore shows 60.0 dB, 60.0 phon, and 4.0 sone. If the target unit is changed to sone, the primary result becomes 4.0 sone. If the source unit is changed to 4 sone, the reverse calculation is:

$\text{phon} = 40 + 10\ \log_{2}\left(4\right) = 60\ \text{phon}$

Then dB is also shown as 60.0 under the 1 kHz assumption.

Reference table

The table illustrates why sones feel more intuitive for perceived loudness: the number doubles every 10 phons. Decibels and phons remain logarithmic-level quantities; sones are the linear loudness estimate in this particular model.

Audio, workplace, and room context

In audio engineering, dB is the everyday measurement language for levels, gain, headroom, and acoustic output. This converter can help explain how a single sound level maps to a loudness scale, but it does not replace calibrated SPL measurements. In workplace noise, dB values are usually weighted, averaged over time, and compared with exposure limits; duration is as important as level. In room acoustics, reflections, distance, absorption, and multiple sources shape the listening experience. The room acoustics calculator is a better companion for space behavior, while this page stays focused on one sound-level value at a time.

For practical listening notes, record the assumption beside the number. A note such as “60 dB, treated as 60 phon at 1 kHz” is clearer than simply writing “4 sones” with no context. It tells the reader that the value came from a loudness model, not from a full equal-loudness contour analysis. That context prevents a quick conversion from being mistaken for a complete psychoacoustic measurement.

Pitfalls

• Do not add dB values directly; use logarithmic sound math.
• Do not treat the dB-to-phon equality as valid for every frequency.
• Do not enter zero sones; the reverse formula needs a logarithm.
• Do not use sone conversion as a hearing-safety threshold.
• Do not compare unweighted dB, dBA, peak dB, and time-weighted averages as if they were the same measurement.

Sources

• OSHA, Occupational Noise Exposure — workplace noise exposure context and hearing-conservation guidance.
• CDC NIOSH, Noise and Hearing Loss Prevention — public-health context for hazardous noise.
• NIST, Guide for the Use of the International System of Units — unit presentation guidance relevant to acoustic units.
• ISO, ISO 532-1:2017 — authoritative scope for estimating loudness from measured sound; unlike this 1 kHz reference conversion, the standard methods use spectral or time-signal data.