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[b] The IEC 60027-3 standard recommends the following format: [14] L x (re x ref) or as L x/x ref, where x is the quantity symbol and x ref is the value of the reference quantity, e.g., L E (re 1 μV/m) = 20 dB or L E/(1 μV/m) = 20 dB for the electric field strength E relative to 1 μV/m reference value. If the measurement result 20 dB is ...
1 dB = 1 / 20 ln 10 is the decibel. The commonly used reference sound power in air is [11] = . The proper notations for sound power level using this reference are L W/(1 pW) or L W (re 1 pW), but the suffix notations dB SWL, dB(SWL), dBSWL, or dB SWL are very common, even if they are not accepted by the SI. [12]
1 Np = 1 is the neper; 1 B = 1 / 2 ln(10) is the bel; 1 dB = 1 / 20 ln(10) is the decibel. The commonly used reference sound intensity in air is [5] = /. being approximately the lowest sound intensity hearable by an undamaged human ear under room conditions.
A 3 dB increase in level is approximately equivalent to doubling the power, which means that a level of 3 dBm corresponds roughly to a power of 2 mW. Similarly, for each 3 dB decrease in level, the power is reduced by about one half, making −3 dBm correspond to a power of about 0.5 mW.
If the power quantity P is proportional to F 2, and if the reference value of the power quantity, P 0, is in the same proportion to F 0 2, the levels L F and L P are equal. The neper , bel , and decibel (one tenth of a bel) are units of level that are often applied to such quantities as power, intensity, or gain. [ 6 ]
They pass both quadratures. For an optical amplifier it holds F o,IQ = n sp (1-1/G)+1/G ≥ 1. Quantity n sp (1-1/G) is the input-referred number of added noise photons per mode. F o,IQ and F pnf can easily be converted into each other. For large G it holds F o,IQ = F pnf /2 or, when expressed in dB, F o,IQ is 3 dB less than F pnf. The ideal F ...
In other words, the phon matches the sound pressure level in decibels of a similarly perceived 1 kHz pure tone. [3] For instance, if a sound is perceived to be equal in intensity to a 1 kHz tone with an SPL of 50 dB, then it has a loudness of 50 phons, regardless of its physical properties. [4]
LKFS and LUFS are identical in that they are both measured in absolute scale and both equal to one decibel (dB). [12] Loudness units (LU) is an additional unit used in EBU R128. It describes L k without direct absolute reference and therefore describes loudness level differences.