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Convert between sones and phons for accurate loudness measurement and acoustic calculations
Subjective loudness unit
Objective loudness level
Reference Point: 1 sone = 40 phons
This reference is based on a 1 kHz tone at 40 dB SPL
phon = 40 + 10 × log₂(sone)
This formula applies for loudness values at or above the reference level
phon = 40 × (sone + 0.0005)^0.35
This formula is used for very quiet sounds below the reference level
sone = 2^((phon - 40) / 10)
Inverse formula for converting phons back to sones
| Sone | Phon | Description |
|---|---|---|
| 0.25 | 24.86 | Very quiet room |
| 0.5 | 31.37 | Quiet library |
| 1 | 40.00 | Reference level (1 kHz at 40 dB) |
| 2 | 50.00 | Twice as loud as reference |
| 4 | 60.00 | Normal conversation |
| 8 | 70.00 | Busy traffic |
| 16 | 80.00 | Loud music |
| 32 | 90.00 | Heavy machinery |
| 64 | 100.00 | Very loud (hearing risk) |
A sone is a unit of subjective loudness. It represents how loud a sound seems to the human ear. The sone scale is linear, meaning that a sound of 2 sones is perceived as twice as loud as a sound of 1 sone.
A phon is a unit of loudness level. It is an objective measure based on the sound pressure level of a 1 kHz tone. A sound has a loudness level of N phons if it sounds as loud as a 1 kHz tone at N dB SPL.
Sone and phon measurements are used in acoustical engineering, environmental noise assessment, audio equipment design, hearing research, and noise pollution studies. They help quantify how humans perceive sound intensity in real-world conditions.