That what's needed for a good specification,
The reason is that the A must be contained in L p A or L W A,Īnd with a proper description. The A in dB(A) is not supported by ISO standards. That's why L p and L W are both expressed in dB, each with a different reference.
It's not a unit because it's the logarithm of a quotient, If A-weighting has been applied, then the descriptors above contain the character A at the end, for example: L pA dB and dB(A)ĭB (abbreviation for decibel) is the "unit" for both pressure and power level. Levels are described in ISO standards, using the following abbreviations or descriptors: SI ( International System of Units) only contains units for pressure and power, not for levels. SPL and SWL, widely used in relation to sound, are confusing and not the correct ones to use for this purpose. "sound power level" although a few decades ago sound power level was abbreviated in the US with PWL.Įven a wikipedia page refers to SPL and SWL as being valid descriptors.īad habits exist, and wikipedia apparently is not always correct. SPL is widely used for "sound pressure level", but these characters could as well describe The definition of SWL? What about:Safe Working Load, or Static Water Level Sound pressure level an operator or bystander is exposed to, in a free field above a reflecting plane. In relation to the Machinery directive we speak about the "emission sound pressure level". Pressure level always depends on position and environment. Given a well defined operation condition, the sound power level of a machine is a fixed value, were the sound To the source(s) and acoustic properties of the surroundings of the source. The sound pressure level is a measure for theĮffect of the energy of an acoustic source (or a collection of sources) and depends on the distance The sound power level indicates the total acoustic energy that a machine, or piece of equipment, radiates to Sound power and pressure level, what's the use?