Search results
Results from the WOW.Com Content Network
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 ...
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.
The decibel (dB) is a dimensionless unit, used for quantifying the ratio between two values, such as signal-to-noise ratio. The dBm is also dimensionless, [ 1 ] [ 2 ] but since it compares to a fixed reference value, the dBm rating is an absolute one.
It is essential to know which category a measurement belongs to when using decibels (dB) for comparing the levels of such quantities. A change of one bel in the level corresponds to a 10× change in power, so when comparing power quantities x and y, the difference is defined to be 10×log 10 (y/x) decibel.
F 0 is the reference value of F. 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]
The decibel watt (dBW or dB W) is a unit for the measurement of the strength of a signal expressed in decibels relative to one watt.It is used because of its capability to express both very large and very small values of power in a short range of number; e.g., 1 milliwatt = −30 dBW, 1 watt = 0 dBW, 10 watts = 10 dBW, 100 watts = 20 dBW, and 1,000,000 W = 60 dBW.
The sound level generated is 94 dB, which corresponds to a root-mean-square sound pressure of 1 pascal and is at a frequency of 1 kHz where all the frequency weightings have the same sensitivity. For a complete sound level meter check, periodic testing outlined in IEC61672.3-2013 should be carried out.
Such a difference can exceed 100 dB which represents a factor of 100,000 in amplitude and a factor 10,000,000,000 in power. [4] [5] The dynamic range of human hearing is roughly 140 dB, [6] [7] varying with frequency, [8] from the threshold of hearing (around −9 dB SPL [8] [9] [10] at 3 kHz) to the threshold of pain (from 120–140 dB SPL [11 ...