Tonal maskers create distinct audible regions beyond simple masking

Evidence

To explain this complicated situation, different regions in the plane outlined in Fig. 4.6 are marked with indications of which sounds are heard by the subject. Below threshold in quiet of the test tone (broken line), nothing but the masker is audible. Below about 700 Hz, increasing the level of the test tone above threshold in quiet produces a region in which the masker tone and the test tone are audible. At frequencies between about 700 Hz and g kHz, the 80-dB I-kHz masker produces a region in which only the masker tone is audible, even though threshold of the test tone in quiet is mU(:~h lower. Areas of audible beats are marked by hatching. The region in which only the masker tone and the difference tone (but not the test tone) are audible is marked by stippling. Above masked threshold of the test tone at frequencies between I and 2 kHz, difference tones are also audible. All these results indicate that thresholds of tones masked by tonal maskers are far more difficult to measure than thresholds of tones masked by noise. — Professor Dr.-Ing. Hugo Fastl, Professor Dr.-Ing. Eberhard, Psychoacoustics- Facts and Models, 434

Categorization

• DEFINE: Maps the distinct perceptual regions produced when a tonal masker suppresses a test tone, contrasting with the cleaner case of noise masking.
• QUESTION: Why is a 1-kHz 80-dB masker able to suppress test tones over a wide region where quiet threshold is far lower - this illustrates upward spread of masking.
• corroborated: 2 independent passages support this claim — Professor Dr.-Ing. Hugo Fastl, Professor Dr.-Ing. Eberhard, Psychoacoustics- Facts and Models, 434
• XREF: connects to: Timbre perception can be analyzed through component-to-component masking interactions — David Howard, Jamie Angus, coustics and Psychoacoustics, 1645