![]() ![]() This allows one to clearly visualize huge changes of some quantity. The decibel's logarithmic nature means that a very large range of ratios can be represented by a convenient number, in a similar manner to scientific notation.The use of the decibel has a number of merits: (In exact terms the power factor is 10 6/10, or about 3.9811, a relative error of about 0.5%.) Similarly, an increase of 3 dB implies an increase in voltage by a factor of approximately √2, or about 1.41, an increase of 6 dB corresponds to approximately four times the power and twice the voltage, and so on. In exact terms, the factor is 10 3/10, or 1.9953, about 0.24% different from exactly 2. It is seen that there is a 10 dB increase (decrease) for each factor 10 increase (decrease) in the ratio of the two power levels, and approximately a 3 dB increase (decrease) for every factor 2 increase (decrease). Thus, if L represents the ratio of a power value P 1 to another power value P 0, then L dB represents that ratio expressed in decibels and is calculated using the formula: ![]() When referring to measurements of power or intensity, a ratio can be expressed in decibels by evaluating ten times the base-10 logarithm of the ratio of the measured quantity to the reference level. In April 2003, the International Committee for Weights and Measures (CIPM) considered a recommendation for the decibel's inclusion in the SI system, but decided not to adopt the decibel as an SI unit. In many situations, however, the bel proved inconveniently large, so the decibel has become more common. It was originally called the transmission unit or TU, but was renamed in 1923 or 1924 in honor of the Bell System's founder and telecommunications pioneer Alexander Graham Bell. The bel was originally devised by engineers of the Bell Telephone Laboratories to quantify the reduction in audio level over a 1 mile (approximately 1.6 km) length of standard telephone cable.
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