The steep lower slope of the excitation pattern determines frequency modulation detection threshold

Evidence

Assuming that the detectors along the critical-band rate scale are only able to react to level changes, it becomes clear that we have to search for the location along the critical-band rate scale that first reaches an excitation-level change of 1 dB as the frequency variation is increased. Figure 7.20 indicates that this would be the position of the lower slope of the excitation level versus critical-band rate pattern. There, the slope is steepest and reaches 27 dB per Bark. The upper slope of the pattern is flatter and produces a 1 dB level increment much later. The excitation level increment of 1 dB is reached at the lower slope when 211f x 27 dB/Bark = 1 dB. — Professor Dr.-Ing. Hugo Fastl, Professor Dr.-Ing. Eberhard, Psychoacoustics- Facts and Models, 1139

Frequency modulation of a sinusoidal tone leads to an excitation level versus critical-band rate pattern that can be approximated by a triangularlike distribution that moves to the left and right along the critical-band rate scale. Figure 7.20 shows such a pattern, where the solid distribution is that of an unmodulated tone and the broken curves correspond to the patterns created by the extreme frequency shifts of the modulation. Assuming that the detectors along the critical-band rate scale are only able to react to level changes, it becomes clear that we have to search for the location along the critical-band rate scale that first reaches an excitation-level change of 1 dB as the frequency variation is increased. Figure 7.20 indicates that this would be the position of the lower slope of the excitation level versus critical-band rate pattern. There, the slope is steepest and reaches 27 dB per Bark. The upper slope of the pattern is flatter and produces a 1 dB level increment much later. — Professor Dr.-Ing. Hugo Fastl, Professor Dr.-Ing. Eberhard, Psychoacoustics- Facts and Models, 1139

Categorization

• DEFINE: Explains how a 1 dB excitation-level change at the detector array defines the just-noticeable frequency variation.
• corroborated: 2 independent passages support this claim — Professor Dr.-Ing. Hugo Fastl, Professor Dr.-Ing. Eberhard, Psychoacoustics- Facts and Models, 1139