When you switch on your audio system, but don't put any music on, you can maybe hear a very faint hiss in the loudspeakers. Its level will depend on how good the hifi system is. The lower the better.
Same applies to the amplifier inside the lnb, and the db figure represents the 'noise'. Lower=better.
Triple Dragon, Dreambox 8000, Echostar AD3000ip, TBS6522,6925,6983 PCie cards.
Gibertini 1.25m motorised dish driven by the AD3000, with either Inverto BU Quad or Norsat / XMW Ka LNBs . SMW 1.05m + 3 other dishes. Speccy: Promax HD Ranger+