Broadband maskers at low levels mask mid frequencies more than extremes.

Evidence

At the lowest levels, broadband maskers were able to mask the mid frequencies but not the low and high frequencies. For example, the −10 dB SPL masker raised the threshold of the 2000-Hz tone from about 7 dB SPL in quiet to about 11 dB SPL, but that same masker did not shift the threshold of the 250 Hz tone at all. At these low masker levels, these frequency effects could be attributed to audibility, as the level of the noise did not exceed the absolute threshold of the low-frequency tones. Once masking began, however, the same noise masked high frequencies slightly more than low frequencies: the 30 dB SPL masker raised the 500-Hz threshold to 48 dB SPL and the 4000-Hz threshold to 52 dB SPL. — Jennifer Lentz, Psychoacoustics- Perception of Normal…, 451

Categorization

• QUESTION: Worth chasing: why does broadband noise mask high frequencies slightly more than low once masking begins — is this tied to unequal basilar-membrane bandwidth or critical-band spread?