Should the acceptable noise level be considered to be an acceptable noise range?

The acceptable noise level (ANL) test is used to quantify the amount of competing background noise (BNL) that a listener is willing to accept when listening to speech at the most comfortable level (MCL). ANL is calculated by subtracting the BNL from the MCL. Most studies show large intersubject ANL variability and a few also demonstrate large intrasubject variability. Very few predictor variables for ANL have been identified and it has been proposed that the ANL depends on an inherent characteristic of the listener. However, some of the variability seems to depend on poor precision of the ANL test. After removing the effect of poor precision, some variability still remains. One possible explanation for these findings may be that the ANL is not a single level but a range of levels. Using recent data, this presentation examines the notion of an acceptable noise range