And Sones - Phons

A 50 dB tone at 100 Hz (low rumble) sounds much quieter than a 50 dB tone at 2000 Hz (mid-range) — even though their physical sound pressure is identical. Why? Human ears are not flat frequency sensors. We are most sensitive to frequencies between 2–5 kHz and less sensitive to very low or very high frequencies.

While Phons tell us which sounds are equally loud, they don't tell us how much louder one sound is than another. For that, we need Sones. 2. What are Sones? (The Linear Scale) phons and sones

Modern broadcasting (e.g., EBU R128) uses (Loudness Units Full Scale). While LUFS is technically related to Phons (it uses a $K$-weighting filter derived from equal-loudness contours), the goal is to normalize the perceived loudness of audio programs. The shift from peak measurement (dB) to loudness normalization is a direct industrial application of the phon/sone principles. A 50 dB tone at 100 Hz (low