Detecting level variation is about 2.5 times harder than detecting level difference

Evidence

Although the data for just-noticeable level variations or just-noticeable level differences depend somewhat on the measurement technique used, the values determined for variations are always larger than those produced for justnoticeable differences. A typical example is given in Fig. 7.4. Two sets of data with a I-kHz tone, one for level changes (left) and another for frequency changes (right), are shown as a function of level. The results produced for level variations (measured as just-noticeable amplitude modulation and indicated by the open circles) decrease from almost 2 dB to about 0.7 dB between 30 and 70 dB sound pressure level. The results for just-noticeable level differences (dots) decrease as a function of level from about 0.7 dB to about 0.3 dB. There is a factor of about 2.5 between the two curves. — Professor Dr.-Ing. Hugo Fastl, Professor Dr.-Ing. Eberhard, Psychoacoustics- Facts and Models, 1034

Categorization

• XREF: Amplitude modulation thresholds (“variations”) vs. level-difference JNDs contrast across two measurement paradigms, echoing Milgrom-style distinctions about how measuring context changes the outcome.