Description: Percentage in a period where the object has fulfilled the function; Name: availability in relation to time
Description: During a given period of time, percentage of the time during which an item was able to perform when required ; Name: Time based availability
Description: through a surface, product of the sound pressure, p, and the component of the particle velocity, un, at a point on the surface in the direction normal to the surface, integrated over that surface; Name: sound power