The sone is a perceptually relevant unit that quantifies how loud a sound feels , rather than its physical energy. Its linear scaling makes it intuitive for comparing loudness differences, and it is essential in product design, architectural acoustics, and hearing research.
This formula is an idealization. The exact sone value for a given dB SPL depends on frequency, as the human ear is not equally sensitive to all frequencies.
| Unit | Measures | Scale | Human Perception | |------|----------|-------|------------------| | | Perceived loudness | Linear (2 sones = twice as loud) | Directly proportional | | Decibel (dB SPL) | Sound pressure (physical) | Logarithmic | Not proportional | | Phon | Loudness level | Logarithmic (matches dB SPL at 1 kHz) | Scale for matching loudness |
The sone is related to the decibel, but the relationship is non-linear. A common approximation used for converting sound pressure level (phon, a unit of loudness level) to sones is: