Such signals may thus demonstrate a relationship between the pressure signal 302 and the density signal 304, as {HEAD ~ those signals} change over {TAIL ~ time} 
change over
Such signals may thus demonstrate a relationship between the pressure signal 302 and the density signal 304 , as { HEAD ~ those signals } change over { TAIL ~ time }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL