Any sound level meter of sufficient accuracy may be used for sound power measurements. However, with this option the NOR118 with do the calculations for you! All you need to do is place your test object properly, enter sound power mode, determine the number of microphone positions (the instrument accepts up to 40 positions!) and then start to measure the background noise in one typical position.
After this the measurement is made for either a parallelpiped or a hemisphere surface and the instrument will do all the calculations for you.
A simple push on the TBL key is all it takes to produce the result table containing the LWA.