Louder signals need disproportionately more dB to double perceived loudness

Evidence

The linear dependence between the SPL in dB and the loudness level in phons is different from the dependence between SPL and loudness in sones introduced in the previous section. The SPL in Figure 10.8 is expressed in dB and the loudness is expressed in sones on a logarithmic scale. A 1-dB change in SPL thus produces very different changes in the value of loudness in sones at low and high levels of the SPL. Technical applications often use the loudness level, since the JND of the SPL of sound events is constant at about 1 dB (or 1 phon) over a wide range of SPLs (Fastl and Zwicker, 2007). A change in a certain number of phons thus corresponds to a similar change in the perceived ‘strength’ of an auditory event, which is beneficial in auditory models and sound and voice techniques. — Ville Pulkki, Matti Karjalainen, Communication Acoustics- An…, 1132

Categorization

• SEED: Angle: why audio mixing/mastering and hearing-aid gain use phon-like scales — practical engineering consequence of the sones-vs-phons nonlinearity.
• SHARE: Worth sending to an audio engineer friend: the 1-dB JND constancy is why phons beat sones for technical loudness work.
• XREF: connects to: Those low in status need stronger signals to compensate for low-status cues — W. David Marx, Status and Culture: How Our Desire for…, 202