Sound power level

Sound power level is a logarithmic rating of the total sound energy radiated by a source per unit of time. In home energy paperwork it most often appears in heat pump datasheets and MCS 020 noise calculations, where the manufacturer's A-weighted sound power figure is used before distance, reflecting surfaces and barriers are considered. It is not the same as sound pressure level, which is the sound level calculated or measured at a particular point. A sound power figure helps compare the source used in a noise calculation, but it does not by itself show how loud the installed heat pump will be at a neighbour's window, prove planning compliance or guarantee that the installation will be acceptable in every operating condition.