Acceptable noise level and psychophysical masking

Individuals with low acceptable noise levels (ANLs) accept more noise than individuals with high ANLs. To determine whether ANL is influenced more by afferent or efferent cortical responsiveness, the authors measured differences in temporal masking responses between individuals with low versus high ANLs. If listeners with low ANLs have masked thresholds similar to those of listeners with high ANLs, low ANLs may be due to reduced afferent responsiveness affecting both the masker and signal. If, however, listeners with low ANLs have masked thresholds better than that of listeners with high ANLs, there may be a physiological basis for improved selective attention via stronger efferent inhibition of the "unwanted" sound.

Participants were 19 listeners with normal hearing between the ages of 19 and 35. Ten listeners had low ANLs and 9 had high ANLs. All participants were compared using tone-in-noise simultaneous, forward, and backward masking tasks.

Results revealed no observed differences in masked thresholds between the low versus high ANL group. The low ANL group, however, required significantly more threshold runs to achieve criterion necessary for threshold determinations.

Findings suggest that low ANLs are associated with reduced afferent cortical responsiveness and, possibly, decreased sustained attention.