Nonsimultaneous masking summation resists simple generalizations

Evidence

The effect expressed as “addition of masking” can be formulated by a question: does threshold masked by the two noises remain the same as threshold masked by one sound alone, or does it rise by 3 dB (intensity addition) or 6 dB (sound pressure addition), or does it rise by some other value? Results of corresponding measurements using simultaneous masking can be summarized relatively clearly. Similar measurements using nonsimultaneous masking, for example post-masking, produce effects that cannot be generalized easily. It seems that bandwidth plays an important role with a number of other variables if temporal parameters are involved. — Professor Dr.-Ing. Hugo Fastl, Professor Dr.-Ing. Eberhard, Psychoacoustics- Facts and Models, 617

Categorization

• DEFINE: Defines ‘addition of masking’ precisely via the question of whether combined-masker thresholds follow intensity addition (3 dB) or sound-pressure addition (6 dB) or neither.
• QUESTION: Why do simultaneous-masking results summarize cleanly while nonsimultaneous do not? What role does bandwidth play with temporal parameters? Worth chasing literature on this asymmetry.