Description: Period of time during which an item performs its intended function, it includes all the time a machine is continuously running from start-up until it is shut down.; Name: ot
Description: passed time period after comissioning of a system, sub-system, component or piping; Name: Operating time 
Description: integral of the sound power, p, over a stated time interval of duration t (starting at t1 and ending at t2); Name: sound energy