Odd-order difference tones explain why single tones mask differently than noise

Evidence

Because five tones produce the same masking as a narrow-band noise, but one single tone produces a much steeper masking slope, it may be possible to find the reason for this difference using the five-tone complex. Using a special procedure, which is explained in detail in Chap. 14, the level of the difference tones produced by the five-tone complex can be estimated. The difference tones of odd order play the most important role. — Professor Dr.-Ing. Hugo Fastl, Professor Dr.-Ing. Eberhard, Psychoacoustics- Facts and Models, 459

Because five tones produce the same masking as a narrow-band noise, but one single tone produces a much steeper masking slope, it may be possible to find the reason for this difference using the five-tone complex. Using a special procedure, which is explained in detail in Chap. 14, the level of the difference tones produced by the five-tone complex can be estimated. The difference tones of odd order play the most important role. … The difference tones of third, fifth, seventh, and ninth order frequency 1. — Professor Dr.-Ing. Hugo Fastl, Professor Dr.-Ing. Eberhard, Psychoacoustics- Facts and Models, 459

Categorization

• XREF: Connects to the mechanics of combination/distortion tones in the cochlea, mirroring nonlinear-systems behavior familiar from physics. — connects to: Fletcher’s equal-power assumption wrongly describes masked-tone thresholds.; Phase differences among wavelets reduce the total difference-tone amplitude; Combination tones arise from the hearing system’s own nonlinearity — Professor Dr.-Ing. Hugo Fastl, Professor Dr.-Ing. Eberhard, Psychoacoustics- Facts and Models, 430 (+2 more)
• QUESTION: What is the special procedure of Chap. 14 that estimates difference-tone levels subjectively?
• corroborated: 3 independent passages support this claim — Professor Dr.-Ing. Hugo Fastl, Professor Dr.-Ing. Eberhard, Psychoacoustics- Facts and Models, 459

Broader Connections

• Combination tones arise from the hearing system’s own nonlinearity #expands (0.75) — Professor Dr.-Ing. Hugo Fastl, Professor Dr.-Ing. Eberhard, Psychoacoustics- Facts and Models, 430
• Combination tones exist below both source tones and vary in audibility #expands (0.72)