Threshold in quiet is attributed to internal physiological noise

Evidence

Threshold in quiet is assumed to be produced by such internal noise. Using the threshold factor, which was helpful in describing the relationship between masking sound and the masked threshold produced by that sound, we are able to calculate the excitation Egr producing threshold in quiet by the test-tone excitation ETQ, using the equation where s is the ratio between the intensity of the just-audible test tone and the intensity of the internal noise appearing within the critical band at the test tone’s frequency. — Professor Dr.-Ing. Hugo Fastl, Professor Dr.-Ing. Eberhard, Psychoacoustics- Facts and Models, 1263

Categorization

• XREF: Connects to the earlier discussion (other chapters) of masking thresholds and the ‘threshold factor’ used to relate masking sound to masked threshold.
• QUESTION: Worth verifying how the same threshold factor bridges the masking case and the internal-noise estimation case.