Decibel | Wikipedia audio article
Channel: wikipedia tts
Date: 2018-12-25

This is an audio version of the Wikipedia Article:
https://en.wikipedia.org/wiki/Decibel


00:02:15 1 History
00:06:25 2 Definition
00:07:01 2.1 Power quantities
00:07:25 2.2 Field quantities and root-power quantities
00:07:42 2.3 Conversions
00:08:59 2.4 Examples
00:10:35 3 Properties
00:11:25 3.1 Reporting large ratios
00:14:32 3.2 Representation of multiplication operations
00:14:52 3.3 Representation of addition operations
00:19:33 4 Uses
00:19:57 4.1 Perception
00:20:32 4.2 Acoustics
00:22:12 4.3 Electronics
00:22:40 4.4 Optics
00:22:50 4.5 Video and digital imaging
00:28:23 5 Suffixes and reference values
00:28:32 5.1 Voltage
00:28:52 5.2 Acoustics
00:31:22 5.3 Audio electronics
00:32:56 5.4 Radar
00:33:31 5.5 Radio power, energy, and field strength
00:35:10 5.6 Antenna measurements
00:37:34 5.7 Other measurements
00:41:34 5.8 List of suffixes in alphabetical order
00:41:38 5.8.1 Unpunctuated suffixes
00:44:16 5.8.2 Suffixes preceded by a space
00:45:52 5.8.3 Suffixes within parentheses
00:46:44 5.8.4 Other suffixes
00:47:19 6 Related units
00:48:43 7 Fractions
00:50:11 8 See also
00:53:49 9 References
00:53:59 10 Further reading
00:56:04 11 External links
01:00:37 Suffixes preceded by a space
01:01:25 Suffixes within parentheses
01:02:05 Other suffixes
01:02:35 Related units
01:03:48 Fractions
01:04:26 3.5 dB/km × 0.1 km.
01:04:34 See also



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SUMMARY
=======
The decibel (symbol: dB) is a unit of measurement used to express the ratio of one value of a physical property to another on a logarithmic scale. It can be used to express a change in value (e.g., +1 dB or −1 dB) or an absolute value. In the latter case, it expresses the ratio of a value to a reference value; when used in this way, the decibel symbol should be appended with a suffix that indicates the reference value, or some other property. For example, if the reference value is 1 volt, then the suffix is "V" (e.g., "20 dBV"), and if the reference value is one milliwatt, then the suffix is "m" (e.g., "20 dBm").There are two different scales used when expressing a ratio in decibels depending on the nature of the quantities: power and field (root-power). When expressing power quantities, the number of decibels is ten times the logarithm to base 10 of the ratio of two power quantities. That is, a change in power by a factor of 10 corresponds to a 10 dB change in level. When expressing field (root-power) quantities, a change in amplitude by a factor of 10 corresponds to a 20 dB change in level. The extra factor of two is due to the logarithm of the quadratic relationship between power and amplitude. The decibel scales differ so that direct comparisons can be made between related power and field quantities when they are expressed in decibels.
The definition of the decibel is based on the measurement of power in telephony of the early 20th century in the Bell System in the United States. One decibel is one tenth (deci-) of one bel, named in honor of Alexander Graham Bell; however, the bel is seldom used. Today, the decibel is used for a wide variety of measurements in science and engineering, most prominently in acoustics, electronics, and control theory. In electronics, the gains of amplifiers, attenuation of signals, and signal-to-noise ratios are often expressed in decibels.
In the International System of Quantities, the decibel is defined as a unit of measurement for quantities of type level or level difference, which are defined as the  logarithm of the ratio of power- or field-type quantities.