A single exponent of 0.23 governs the loudness power law

Evidence

The most important value in this equation is the exponent k. It can be approximated quite simply by using the dependence of the loudness of uniformexciting noise as a function of its level, as mentioned in the preceding section. — Professor Dr.-Ing. Hugo Fastl, Professor Dr.-Ing. Eberhard, Psychoacoustics- Facts and Models, 1268