For the gap marker, white noise was low-pass filtered at cutoff frequencies of 1, 2, and 4 kHz, respectively, via 3000th-order finite impulse response filter with an approximately -116 dB/octave filter slope.
The gap thresholds of groups varying in terms of gap marker cutoff frequency are shown in Figure 2.
Then, data derived from different groups with the same gap marker frequency were analyzed by one-way ANOVA.
* indicates gap thresholds of the 1 kHz mild, moderate, and severe HF SNHL groups with 1 kHz gap marker which were significantly higher than those of the NH group and the 4 kHz mild HF SNHL group; # indicates gap thresholds of the 4 kHz moderate HF SNHL group which were significantly higher than those of the NH group for 4 kHz gap marker.