Sound power level
This is a measure of how much power emitted to the environment. The sound power level is in most cases independent of the placement in the room.
A-weighting filter is the most commonly used, and is applicable for normal frequencies and ljustyrkor. A-weighting attenuates the low frequencies and amplifies the medium, A-weighted filter is primarily intended to be used in the measurement of the level sounds
B-weighted filter is supposed to handle the between loud sounds but these B-weighted filter is used rarely lower.
C-weighted filter is for the loudest sounds sound filter with a C-weighting is used mainly for sound with strong and low frequencies such as fan noise but is also used for short, sharp beeps mean when the C-weighted filters do not suppress the low frequencies in contrast to the A-weighted filter.
The decibel (dB)
Is a logarithmic measure that indicates a relation to a reference value. Commonly used in sound determinations, but also occur in other areas. The basic unit is actually Bel but used almost exclusively with the prefix deci ie 10.1 Bel.