a noise reducing groove formed at {HEAD ~ an upper surface} of the pump cover and having {TAIL ~ a predetermined length}; and 
a noise reducing groove formed at { HEAD ~ an upper surface } of the pump cover and having { TAIL ~ a predetermined length } ; and
OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH