In telecommunication

Telecommunication

Telecommunication is the transmission of information over significant distances to communicate. In earlier times, telecommunications involved the use of visual signals, such as beacons, smoke signals, semaphore telegraphs, signal flags, and optical heliographs, or audio messages via coded...

, reference noise is the magnitude of circuit

Telecommunication circuit

A telecommunication circuit is any line, conductor, or other conduit by which information is transmitted.A dedicated circuit, private circuit, or leased line is a line that is dedicated to only one use...

 noise

Noise

In common use, the word noise means any unwanted sound. In both analog and digital electronics, noise is random unwanted perturbation to a wanted signal; it is called noise as a generalisation of the acoustic noise heard when listening to a weak radio transmission with significant electrical noise...

 chosen as a reference for measurement.

Many different levels with a number of different weightings are in current use, and care must be taken to ensure that the proper parameters are stated.

Specific ones include: dBa

A-weighting

A Weighting curve is a graph of a set of factors, that are used to 'weight' measured values of a variable according to their importance in relation to some outcome. The most commonly known example is frequency weighting in sound level measurement where a specific set of weighting curves known as A,...

, dBa(F1A), dBa(HA1), dBa0, dBm

DBm

dBm is an abbreviation for the power ratio in decibels of the measured power referenced to one milliwatt . It is used in radio, microwave and fiber optic networks as a convenient measure of absolute power because of its capability to express both very large and very small values in a short form...

, dBm(psoph), dBm0

DBm0

dBm0 is an abbreviation for the power in dBm measured at a zero transmission level point.dBm0 is a concept used in audio/telephony processing since it allows a smooth integration of analog and digital chains...

, dBrn

DBrn

The symbol dBrn or dB is an abbreviation for decibels above reference noise.Weighted noise power in dB is referred to 1.0 picowatt. Thus, 0 dBrn = -90 dBm...

, dBrnC

DBrnC

dBrnC represents an audio level measurement, typically in a telephone circuit, relative to the circuit noise level, with the measurement of this level frequency-weighted by a standard C-message weighting filter. The C-message weighting filter was chiefly used in North America. The Psophometric...

, dBrnC0, dBrn(f₁-f₂), dBrn(144-line), dBx.