What is the sound pressure level? What is the sound power level?

Simple explanation of the sound pressure level | sound power level:

Imagine standing in a room with a microphone and measuring how loud you think something is - that's the Sound pressure level. The closer you are to the sound source, the louder it is measured - and the further away, the quieter.
The Sound power level on the other hand, describes how much sound is emitted by a source in total - it remains the same no matter where you are in the room.

 

A precise definition of the sound pressure level | sound power level:

  • Sound pressure level (Lₚ) measures the sound pressure relative to a standard reference value of 20 µPa (reference value for air). The formula is
    Lₚ = 20 - log₁₀( p̃ / p₀ ) [dB] or Lₚ = 10 - log₁₀( p̃² / p₀² ) [dB].
    It is a location-dependent variable that changes with the distance to the source. A typical value: the sound pressure level decreases by around 6 dB when the distance is doubled.

  • Sound power level (Lₐw) indicates the total sound energy emitted by a source. It is independent of the distance and the acoustic conditions in the room and can be used for standardized emission specifications. The sound pressure level at a specific location can be calculated from this, taking into account the room conditions

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