Posted By AlB I have scoured the internet for answers with regards to sound and noise. The company I work for are installing a new item of machinery, which will have a Sound Power Level of 100dB. Is this more or less the same as having the machinery in a quiet room, no wind and no other noise source, and taking Sound Pressure Measurements which would read a level of 100dB also? Or have I misunderstood the concept and in fact Power and Pressure are two totally different things and there is no way of determining Pressure from the manufacturers' Power record?