Mean binaural masking level differences (BMLDs) averaged across the individual BMLDs of the thirteen listeners. Left two columns show data for the NNP4 condition, right two columns for the NNP8 condition. Open symbols indicate the BMLD without a precursor, filled symbols indicate conditions where the precursor (with a notch width of 400 Hz and 800 Hz, respectively), was present. To aid visibility, the BMLDs without a precursor (open symbols) are slightly shifted to the left and those with a precursor (filled symbols) are shifted to the right. Error bars indicate plus and minus one standard error.