Third-octave loudness computation requires steady sounds but handles any spectrum

Evidence

Secondly, the additional specific loudness produced by the cut-off slope in the abutting filter towards lower frequencies is taken into account by changing the exponent of specific loudness slightly from 0.23 to 0.25. Because the measurement of all the third-octave band levels needs a certain time, the graphical procedure and that using the computer program are meant only for relatively steady-state sounds. — Professor Dr.-Ing. Hugo Fastl, Professor Dr.-Ing. Eberhard, Psychoacoustics- Facts and Models, 1311