Equivalent pulse code modulation noise
Encyclopedia
In telecommunication
, equivalent pulse code modulation noise (PCM) is the amount of thermal noise power
on a frequency-division multiplexing
(FDM) or wire channel
necessary to approximate the same judgment of speech quality created by quantizing noise in a PCM
channel.
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...
, equivalent pulse code modulation noise (PCM) is the amount of thermal noise power
Power (physics)
In physics, power is the rate at which energy is transferred, used, or transformed. For example, the rate at which a light bulb transforms electrical energy into heat and light is measured in watts—the more wattage, the more power, or equivalently the more electrical energy is used per unit...
on a frequency-division multiplexing
Frequency-division multiplexing
Frequency-division multiplexing is a form of signal multiplexing which involves assigning non-overlapping frequency ranges to different signals or to each "user" of a medium.- Telephone :...
(FDM) or wire channel
Channel (communications)
In telecommunications and computer networking, a communication channel, or channel, refers either to a physical transmission medium such as a wire, or to a logical connection over a multiplexed medium such as a radio channel...
necessary to approximate the same judgment of speech quality created by quantizing noise in a PCM
Pulse-code modulation
Pulse-code modulation is a method used to digitally represent sampled analog signals. It is the standard form for digital audio in computers and various Blu-ray, Compact Disc and DVD formats, as well as other uses such as digital telephone systems...
channel.
- Note 1: The speech quality judgment is based on comparative tests.
- Note 2: Generally, 33.5 dBrnCDBrnCdBrnC 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...
±2.5 dBDecibelThe decibel is a logarithmic unit that indicates the ratio of a physical quantity relative to a specified or implied reference level. A ratio in decibels is ten times the logarithm to base 10 of the ratio of two power quantities...
is considered the approximate equivalent PCM noise of a 7-bitBitA bit is the basic unit of information in computing and telecommunications; it is the amount of information stored by a digital device or other physical system that exists in one of two possible distinct states...
PCM systemSystemSystem is a set of interacting or interdependent components forming an integrated whole....
.