The sound power level (SWL)В helps us around this. If we take a large plant enclosure, with many different machines from different manufacturers, who all give us noise data as a sound pressure level, but all measured at varying distances, some in a lab, some outside, some in an anechoic chamber (or very often not referencing how it was measured at all which is effectively useless data as it could be measured at 1m or 10m!), weвЂ™ll have a hard time predicting the sum of noise levels from our plant enclosure. reflections from the ground, or if inside the surfaces of the room and therefore the reverberation time and volume of the room.В So if we measure the SPL of a fan unit inside a plant room, and move this fan outside, the SPL is unlikely to be the same because of more sound energy escaping into the atmosphere.В Similarly, if the unit is in the corner of a room, condensing sound radiation by the surfaces close around it, and then move this unit into the centre of the room on the floor, where it radiates more hemi spherically, the SPL will be different.В Simply moving further away from a sound source, will reduce the SPL, particularly noticeable when outside. The sound pressure level (SPL) depends on distance, the position of the source and the environment, i.e. weighted to a single number (dB(A)), or a level difference such as a Dw.ДЄ sound power levelВ (SWL) is theoretical.В A sound power is in Watts (W), a sound power level like above, is in dB, a logarithmic ratio of the sound power over a reference sound power.В W for Watts, hence S WL (as SPL is already taken!)В IвЂ™ll explain more shortly. вЂthis unit has a level of 60 dBвЂ™.В Unfortunately, based on that alone, I canвЂ™t do a great deal, without making a lot of assumptions.В If you tell me itвЂ™s 140 dB I know itвЂ™s going to be very loud and problematic!В But at 60 dB, depending on the situation, itвЂ™s difficult to assess the risk.ДЄ sound pressure is the pressure deviation from atmospheric pressure caused by a sound wave, in pascals.В The sound pressure levelВ (SPL) is a logarithmic measure of the ratio of a sound pressure over a reference sound pressure (corresponding to the hearing threshold of a young, healthy ear), quoted as a dB.В If these two pressures are the same, we have an SPL of 0 dB.ДЄ sound pressure levelВ is what we can physically measure using a sound level meter.В Most noise level parameters in a report are based upon an SPL, albeit they are mostly adjusted in some way, i.e.

The difference between sound pressure and sound power can be tricky to get your head around.В For predicting noise levels from noise polluting sources like plant, it is very important.ДЄs a consultant, IвЂ™m often verbally quoted noise levels by clients, i.e.

Db sound reference