highly significantP < 0.05
As shown in Figure 2 , for the intervention group, the reductions were 7.31 dB at 500 Hz, 6.73 dB at 1000 Hz, 6.66 dB at 2000 Hz and 6.92 dB at 4000 Hz, which were all highly significant ( P < 0.05).
As shown in Figure 2 , for the intervention group, the reductions were 7.31 dB at 500 Hz, 6.73 dB at 1000 Hz, 6.66 dB at 2000 Hz and 6.92 dB at 4000 Hz, which were all highly significant ( P < 0.05).