Unwanted sound from whatever source is called noise. Most people at work are exposed to various sound sources (PC, printer, telephone, speech, street sound, air conditioners, etc.). If the noise level is too high, conversation may become difficult and distraction may occur.

Therefore it is important to keep the overall noise level as low as possible at workplaces and also in private life.

- A-weighted Sound Power Level (LWAd) in Bel (B) is a logarithmic quantity of the rate of acoustic energy emitted by a product into the environment. Sound power level is independent of the environment. Note that “Bel” (B) is used for Sound Power Level of IT equipment to avoid confusion with the topic Sound Pressure Levels (see below). Sound power level is the primary descriptor of noise emissions from IT products. “A-weighting” represents the response of the human ear at moderate intensity levels, which reflects people’s perception of loudness.

- A-weighted Sound Pressure Level (LpAm) in deciBel (dB) is a logarithmic quantity of the sound pressure at a specific location. The sound pressure level depends on the sound power level of a product, the distance from the source and the room in which the product is located. If “A-weighting” is used, deciBel is sometimes abbreviated “dB(A)” instead of “dB”.