| Feature | Decibel (dB SPL) | Phon | Sone | | :--- | :--- | :--- | :--- | | | Physical Acoustics | Psychoacoustics | Psychoacoustics | | Scale Type | Logarithmic Ratio | Logarithmic Interval | Ratio (Linear) | | Reference | $20 \mu Pa$ (Pressure) | 1 kHz Tone (Equal Loudness) | 1 kHz Tone at 40 dB | | Zero Point | $10^-12 W/m^2$ (Physical threshold) | Not a true zero (Relative) | Absolute Zero (Silence) | | Usage | Microphone readings, Engineering specs | Weighting filters, Equalization | Noise annoyance, Broadcast loudness | | Key Behavior | 10 dB increase = 10x power | 10 Phon increase = 10 dB at 1 kHz | 10 Phon increase = 2x loudness |
The dynamic range of the human ear spans approximately $10^12$ units of intensity (from the threshold of hearing to the threshold of pain). To manage this vast range, the decibel scale is employed, defined as: phons and sones
$$ L_N = 40 + 33.22 \log_10(N) $$
The sone is a unit of measurement that's more directly related to the perceived loudness of a sound. One sone is defined as the loudness of a sound that is perceived as equally loud as a 1000 Hz tone with a sound pressure level of 40 dB, which is equivalent to 40 phons. | Feature | Decibel (dB SPL) | Phon