Partial masking of a tone by background noise diminishes as tone level rises

Evidence

Additional pink noise with about 55 dB overall level (40 dB per 1/3 octave band) reduces the loudness of a 1 kHz tone by different amounts, depending on the level of the tone. Partial masking decreases with increasing level of the tone: levels of 40 dB, 50 dB, and 60 dB are presented. — Professor Dr.-Ing. Hugo Fastl, Professor Dr.-Ing. Eberhard, Psychoacoustics- Facts and Models, 3323