Before revision:  Due to the multi-band and multi-time strategy , the vocoder speed is increased by 2.75x on a single CPU and the MOS (mean opinion score)degradation is slight .
After revision:  Due to the multi-band and multi-time strategy , the vocoder speed is increased by 2.75x on a single CPU without much MOS degradatiaon (4.57 vs. 4.45) .