The spectrum is measured over {TAIL ~ a time period} of 1 to 1000 seconds, at intervals of {HEAD ~ 5 to 10 milliseconds} or less 
The spectrum is measured over { TAIL ~ a time period } of 1 to 1000 seconds , at intervals of { HEAD ~ 5 to 10 milliseconds } or less
OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH