Thus, {HEAD ~ the same amount} of air flow may be provided by {TAIL ~ lower speed operation}, so that noise performance can be improved 
provided by
Thus , { HEAD ~ the same amount } of air flow may be provided by { TAIL ~ lower speed operation } , so that noise performance can be improved
OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH