The near-miss of Weber’s law means threshold slopes can reach 3 to 6

Evidence

The failure to produce a 45 0 line exactly is called the near-miss of Weber’s law, which describes the audibility of an increment in level for tones. The higher the test-tone frequency, the more the slopes of the rising curves deviate from the 45° slope. The solid lines in Fig. 4.9 represent test-tone frequencies above the masker frequency. The lines remain flat at low masker levels at the threshold in quiet but rise more and more steeply with increasing test-tone frequency. Instead of a slope of 1, the curve for the test-t.one frequency of 6 kHz shows a slope as high as 3. Hence t.he increase in threshold level of the test tone is three times larger than the increase in masker level. The data given in Fig. 4.9 represent average values. Individual data for single subjects sometimes yield slopes as steep as 6. This means that an increment in masker level of 1 dB can produce an increment in the masked threshold of the test tone of up to 6 dB. — Professor Dr.-Ing. Hugo Fastl, Professor Dr.-Ing. Eberhard, Psychoacoustics- Facts and Models, 446

Categorization

• DEFINE: Formally names and defines the ‘near-miss of Weber’s law’ phenomenon for tone level increments, with quantified slope magnitudes.