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The decibel originates from methods used to quantify signal loss in telegraph and telephone circuits. Until the mid-1920s, the unit for loss was miles of standard cable (MSC). 1 MSC corresponded to the loss of power over one mile (approximately 1.6 km) of standard telephone cable at a frequency of 5000 radians per second (795.8 Hz), and matched closely the smallest attenuation detectable to a ...
The sensitivity of a microphone is usually expressed as the sound field strength in decibels (dB) relative to 1 V/Pa (Pa = N/m 2) or as the transfer factor in millivolts per pascal (mV/Pa) into an open circuit or into a 1 kiloohm load. [citation needed] The sensitivity of a loudspeaker is usually expressed as dB / 2.83 V RMS at 1 metre.
dBm or dB mW (decibel-milliwatts) is a unit of power level expressed using a logarithmic decibel (dB) scale respective to one milliwatt (mW). It is commonly used by radio, microwave and fiber-optical communication technicians & engineers to measure the power of system transmissions on a log scale , which can express both very large and very ...
A gain greater than one (greater than zero dB), that is, amplification, is the defining property of an active component or circuit, while a passive circuit will have a gain of less than one. [ 4 ] The term gain alone is ambiguous, and can refer to the ratio of output to input voltage ( voltage gain ), current ( current gain ) or electric power ...
dBc (decibels relative to the carrier) is the power ratio of a signal to a carrier signal, expressed in decibels.For example, phase noise is expressed in dBc/Hz at a given frequency offset from the carrier. dBc can also be used as a measurement of Spurious-Free Dynamic Range between the desired signal and unwanted spurious outputs resulting from the use of signal converters such as a digital ...
Vinyl microgroove phonograph records typically yield 55-65 dB, though the first play of the higher-fidelity outer rings can achieve a dynamic range of 70 dB. [25] German magnetic tape in 1941 was reported to have had a dynamic range of 60 dB, [26] though modern-day restoration experts of such tapes note 45-50 dB as the observed dynamic range. [27]
Substituting the definitions of SNR, signal, and noise in decibels into the above equation results in an important formula for calculating the signal to noise ratio in decibels, when the signal and noise are also in decibels: =,,.
The amplitude of a digital signal can be represented in percent; full scale; or decibels, full scale (dBFS). In analog systems, full scale may be defined by the maximum voltage available, or the maximum deflection (full scale deflection or FSD) or indication of an analog instrument such as a moving coil meter or galvanometer.