Decibel and List of GMA Network original programming: Difference between pages

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The '''decibel''' ('''dB''') is a measure of the [[ratio]] between two quantities, and is used in a wide variety of measurements in [[acoustics]], [[physics]] and [[electronics]]. While originally only used for [[power (physics)|power]] and [[Intensity (physics)|intensity]] ratios, it has come to be used more generally in [[engineering]]. The decibel is widely used in measurements of the [[loudness]] of [[sound]]. It is a "[[dimensionless unit]]" like [[percent]]. Decibels are useful because they allow even very large or small ratios to be represented with a conveniently small number (similar to [[scientific notation]]). This is achieved by using a [[logarithm]].

'''[[GMA Network]]'s programs''' include news and current affairs shows, [[documentaries]], [[drama]]s, dubbed foreign serials, entertainment, news and talk shows, game shows, variety shows, musicals, sitcoms, children's shows, fantasy and reality shows.

== History of bels and decibels ==

For the previously aired and defunct shows of the network, please see the [[list of shows previously aired by GMA Network]].

The '''bel''' (symbol '''B''') is mostly used in [[telecommunication]], [[electronics]], and [[acoustics]]. Invented by engineers of the [[Bell Labs|Bell Telephone Laboratory]] to quantify the reduction in audio level over a 1 [[mile]] (1.6 km) length of standard [[telephone]] cable, it was originally called the ''transmission unit'' or ''TU'', but was renamed in [[1923]] or [[1924]] in honor of the [[laboratory]]'s founder and telecommunications pioneer [[Alexander Graham Bell]].

==GMA Network programs==

The bel was too large for everyday use, so the '''decibel (dB)''', equal to 0.1 '''bel (B)''', became more commonly used. The bel is still used to represent noise power levels in [[hard drive]] specifications. The [[Richter scale]] uses numbers expressed in bels as well, though they are not labeled with a unit. In spectrometry and optics, the absorbance unit used to measure [[optical density]] is equivalent to −1 B. In astronomy, the [[apparent magnitude]] measures the brightness of stars logarithmically, since just as the ear responds logarithmically to acoustic power, the eye responds logarithmically to brightness.

===Local programs===

====[[GMA News and Public Affairs]]====

[[Image:GMANewsLogo.png|right|200px]]

*''[[100% Pinoy]]

*''[[24 Oras]]

*''[[Emergency (TV program)|Emergency]]

*''[[GMA Flash Report]]

*''[[GMA Weekend Report]]

*''[[Imbestigador]]

*''[[I-Witness]]

*''[[Kapuso Mo, Jessica Soho]]

*''[[Kay Susan Tayo]]

*''[[Palaban]]

*''[[Pinoy Meets World]]

*''[[Reporter's Notebook]]

*''[[Saksi]]

*''[[Sine Totoo]]

*''[[Unang Hirit]]

====GMA Definition KiliTV====

[[Image:gma kilitv.jpg|right|150px]]

*''[[Bahay Mo Ba 'To]]

*''[[Bitoy's Funniest Videos]]

*''[[Bubble Gang]]

*''[[Daddy Di Do Du]]

*''[[HP: Ibang Level Na!]]

*''[[Nuts Entertainment]]

*''[[Who's Your Daddy Now?]]

====GMA Telebabad====

A decibel is defined in two common ways.

*''[[Impostora]]

*''[[Lupin (Philippine TV series)|Lupin]]

*''[[Mga Mata ni Anghelita]]

====GMA Dramarama sa Hapon====

When referring to measurements of ''power'' it is:

*''[[Daisy Siete|Daisy Siete Season 15: Isla Chikita]]

*''[[Pati Ba Pintig ng Puso]]

*''[[Sinasamba Kita]]

====Sabado Star Power====

:<math> X_\mathrm{dB} = 10 \log_{10} \bigg(\frac{X}{X_0}\bigg) \ </math>

*''[[Fantastic Man]]

*''Kapuso Sine Special

*''[[Startalk]]

*''[[Wish Ko Lang]]

*''[[Walang Tulugan with the Master Showman]]

====Linggo Bingo====

But when referring to measurements of ''voltage'' it is:

*''[[All Star K!]]

*''[[Boys Nxt Door]]

*''[[Mel and Joey]]

*''[[Mga Kuwento ni Lola Basyang]]

*''[[Move: The Search For Billy Crawford's Pinoy Dancers]]

*''[[Showbiz Central]]

*''SNBO (Sunday Night Box Office)

*''[[SOP Rules]]

*''[[Tok! Tok! Tok! Isang Milyon Pasok!]]

====Other programs====

:<math> X_\mathrm{dB} = 20 \log_{10} \bigg(\frac{X}{X_0}\bigg) \ </math>

*''[[Art Angel]]

*''[[Eat Bulaga!]]

*''[[Diyos at Bayan]]

*''[[Kapwa Ko Mahal Ko]]

*''[[Lovely Day: LD Force]]

*''[[Magpakailanman]]

*''[[Maynila (TV series)|Maynila]]

*''[[Sis (Philippine TV program)|Sis]]

*''[[Just Joking]]

===Foreign/canned shows===

where ''X''₀ is a specified reference. In many cases, the reference is 1 and so is ignored. Which one people use depends on convention and context. When the [[impedance]] is held constant, the power is proportional to the square of the voltage, and so the above two definitions become consistent.

====Asianovelas====

*''[[Great Teacher Onizuka#Live-Action|GTO: Live-Action]]''

*''[[Jumong (TV series)|Jumong]]

*''[[Love Truly]]''

*''[[Love in Heaven]]''

====Animé====

An [[Intensity (physics)|intensity]] ''I'' or [[power (physics)|power]] ''P'' can be expressed in decibels with the standard equation

*''[[Bleach (manga)|Bleach]]''

*''[[Card Captor Sakura]]''

*''[[Case Closed|Detective Conan]]''

*''[[Chrono Crusade]]''

*''[[Dragon Ball Z]]''

*''[[Fullmetal Alchemist]]''

*''[[Ghostfighter]]''

*''[[Fighting Spirit|Knockout]]''

*''[[Machine Robo Rescue]]''

*''[[One Piece]]

*''[[Pokemon]]''

*''[[Rockman Exe]]''

*''[[Samurai 7]]

*''[[The Slayers]]''

*''[[Slamdunk]]''

====Tokusatsu====

:<math>

*''[[Kamen Rider Blade]]''

I_\mathrm{dB} = 10 \log_{10} \left(\frac{I}{I_0} \right) \quad \mathrm{or} \quad P_\mathrm{dB} = 10 \log_{10} \left(\frac{P}{P_0} \right)\ ,

*''[[Genseishin Justiriser]]''

</math>

where ''I''₀ and ''P''₀ are a specified reference intensity and power.

===RGMA programs nationwide===

== Examples ==

*Newscasts

**''[[Balitang Bisdak]]'' -regional newscast of GMA Cebu

**''[[Ratsada]]'' - regional newscast of GMA Iloilo and Bacolod

**''[[Testigo]]'' -regional newscast of GMA Davao

*Variety

**''[[Bongga!]]'' - regional variety show produced by GMA Entertainment Group for GMA Iloilo and Bacolod

**''[[Kuyaw!]]''- regional variety show produced by GMA Entertainment Group for GMA Davao

**''[[Oi! (TV program)|Oi!]]''- regional variety show produced by GMA Entertainment Group for GMA Cebu

==GMA Network upcoming programs==

As examples, if ''P''_dB is 10&nbsp;dB greater than ''P''_dB0, then ''P'' is ten times ''P''₀. If ''P''_dB is 3&nbsp;dB greater, the power ratio is very close to a factor of two (<math>10^{3 \over 10} = 1.99526</math>).

===Local Programs===

*Angela Markado<ref name="multiple"/>

*[[Celebrity Duets (Philippine TV series)|Celebrity Duets]]<ref>{{cite web | last = Barrameda | first = Joe | title = John Estrada, idolo ng kalalakihan | publisher = Abante Tonight | date =[[June 12]], [[2007]] | url =http://abante-tonite.com/issue/june1107/showbiz_jb.htm | accessdate = June 12 | language = [[Filipino language|Filipino]]}}</ref> (July 2007)

*Dyesebel<ref name="multiple"/>

*[[Fulhaus]]<ref>{{cite web | last = Diones | first = Allan | title = FIRST READ ON PEP: Pia Guanio is Vic Sotto's leading lady in new GMA-7 sitcom "Fulhaus" | publisher = Philippine Entertainment Portal | date =[[June 28]], [[2007]] | url =http://www.pep.ph/news/13828/FIRST-READ-ON-PEP:-Pia-Guanio-is-Vic-Sottos-leading-lady-in-new-GMA-7-sitcom-Fulhaus | accessdate = June 28}}</ref> (September 2007)

*Igorota<ref name="multiple"/>

*[[Kamandag]]<ref name="multiple"/> (2008)

*[[L.U.V. Pow]]<ref>{{cite web | last = Erece | first = Dinno | title = GMA-7 unleashes its new shows for 2007 | publisher = Philippine Entertainment Portal | date =[[January 19]], [[2007]] | url =http://www.pep.ph/articles/news/11932.htm | accessdate = January 27 }}</ref> (September 2007)

*[[Magic Kamison|Magic Kamison: Season 2]]<ref> (2008)[http://pep.ph/news/12505/Alex-de-Rossi-ready-to-work-with-Jennylyn-Mercado-in-&%2339;Super-Twins& Alex de Rossi ready to work with Jennylyn Mercado in 'Super Twins'], ''pep.ph'', n.d. Accessed last May 21, 2007.</ref> (2008)

*[[Marimar (Philippine TV series)|Marimar]]<ref name="multiple">{{cite web | last = Lorenzo | first = Alfie | title = GMA 7, siksik sa mga pasabog | publisher = Abante Tonight | date =[[February 5]], [[2007]] | url =http://www.abante-tonite.com/issue/feb0507/showbiz_al.htm | accessdate = February 22 | language = [[Filipino language|Filipino]]}}</ref> (September 2007)

*Rosang Agimat<ref name="multiple"/>

*[[Shaider (Philippine TV series)|Shaider]]<ref>[http://www.pep.ph/news/13214/GMA-7-to-serialize-Mga-Mata-ni-Angelita-of-the-late-Julie-Vega "GMA-7 to serialize Mga Mata ni Angelita of the late Julie Vega"], '' mb.com.ph'', n.d. Accessed last April 12, 2007.</ref> (2007)

*[[Sine Novela]]<ref name="multiple"/>

# [[Kung Mahawi Man Ang Ulap]]

# Saan Darating Ang Umaga

# Dapat Ka Bang Mahalin

# Gaano Kadalas Ang Minsan

# Saan Nagtatago Ang Pag-ibig

# Paano Ba Ang Mangarap

# Kung Aagawin Mo Ang Lahat Sa Akin

# Tayong Dalawa

# Ikaw Naman Ang Iiyak

*[[StarStruck|StarStruck: The Star Explosion]]<ref>{{cite web | last = E. Bautista | first = Mario | title = Starstruck Top 6 to get maximum exposure | publisher = Journal Online | date =[[April 10]], [[2007]] | url =http://www.journal.com.ph/index.php?issue=2007-04-10&sec=3&aid=14564 | accessdate = June 6}}</ref> (December 2007)

*[[Super Twins#Season 2|Super Twins: Season 2]]<ref>{{cite web | last = Asiñas | first = Noel | title = Na-‘X’ na ‘MKM’ episode, lumusot sa MTRCB! | publisher = Journal Online | date =[[June 6]], [[2007]] | url =http://www.journal.com.ph/index.php?issue=2007-06-06&sec=3&aid=20470 | accessdate = June 6}}</ref> (March 2008)

*[[Tasya Fantasya]]<ref name="multiple"/>

*Untitled Philippine-China Co-Production<ref>{{cite web | last = Asiñas | first = Noel | title = China makikisosyo sa GMA-7 | publisher = Journal Online | date =[[June 13]], [[2007]] | url =http://www.journal.com.ph/index.php?issue=2007-06-14&sec=3&aid=21319 | accessdate = June 13}}</ref>

*Zimatar<ref name="multiple"/>

==Special Shows==

For [[sound intensity]], ''I''₀ is typically chosen to be 10⁻¹²&nbsp;W/m², which is roughly the [[threshold of hearing]]. When this choice is made, the units are said to be "dB&nbsp;[[Sound intensity level|SIL]]". For sound power, ''P''₀ is typically chosen to be 10⁻¹²&nbsp;W, and the units are then "dB&nbsp;[[Sound power level|SWL]]".

*[[Kapusolympics]]: The GMA 57th Anniversary Special (July 1, 2007)

==References==

== Electrical circuits ==

<!--<nowiki>

See http://en.wikipedia.org/wiki/Wikipedia:Footnotes for an explanation of how to generate footnotes using the <ref> and </ref> tags, and the template below.

</nowiki>-->

{{reflist}}

==See also==

In electrical circuits, the dissipated power is typically proportional to the square of the [[voltage]] ''V'', and for sound waves, the transmitted power is similarly proportional to the square of the [[pressure (physics)|pressure]] amplitude ''p''. Effective [[sound pressure]] is related to [[sound intensity]] ''I'', [[air density|density]] ''ρ'' and [[speed of sound]] ''c'' by the following equation:

*[[GMA Network]]

:<math>I = p_e^2 / \rho_0 c</math>

*[[List of Philippine television shows]]

*[[GMA Pinoy TV]]

*[[List of programs broadcast by Q]]

*[[List of shows previously aired by GMA Network]]

==External links==

Substituting a measured voltage or pressure and a reference voltage or pressure and rearranging terms leads to the following equations and accounts for the difference between the multiplier of 10 for intensity or power and 20 for voltage or pressure:

*[http://www.igma.tv Official Website of GMA Network]

:<math>

*[http://www.gmapinoytv.com Official Website of GMA Pinoy TV]

V_\mathrm{dB} =20 \log_{10} \left (\frac{V_1}{V_0} \right ) \quad \mathrm{or} \quad p_\mathrm{dB} = 20 \log_{10} \left (\frac{p_1}{p_0} \right )\ ,

</math>

where ''V''₀ and ''p''₀ are a specified reference voltage and pressure. This means a 20 dB increase for every factor 10 increase in the voltage or pressure ratio, or approximately 6 dB increase for every factor 2. Note that in [[physics]], decibels refer to power ratios only; it is incorrect to use them if the [[electrical impedance|electrical]] or [[acoustic impedance]]s are not the same at the two points where the voltage or pressure are measured, though this usage is very common in [[engineering]]. For example, the power carried by a sound wave at atmospheric pressure is only proportional to the squared pressure amplitude as long as the latter is much smaller than 1 atmosphere.

{{Programs}}

== Standards ==

[[Category:GMA Network| ]]

The decibel is not an [[SI]] unit, although the [[Bureau International des Poids et Mesures|International Committee for Weights and Measures]] (BIPM) has recommended its inclusion in the SI system. Following the SI convention, the ''d'' is lowercase, as it is the SI prefix ''deci-'', and the ''B'' is capitalized, as it is an abbreviation of a name-derived unit, the ''bel'', named for [[Alexander Graham Bell]]. Written out it becomes ''decibel''. This is standard [[English language|English]] capitalization.

[[Category:Lists of television series by network|GMA Network]]

[[tl:Tala ng mga palabas ng GMA Network]]

=== Merits ===

The use of decibels has a number of merits:

* It is more convenient to add the decibel values of, for instance, two consecutive [[amplifier]]s rather than to multiply their amplification factors.

* A very large range of ratios can be expressed with decibel values in a range of moderate size, allowing one to clearly visualize huge changes of some quantity. (See [[Bode plot]] and half logarithm graph.)

* In acoustics, the decibel scale was adopted for measuring sound intensity, which, according to [[Weber–Fechner law|Fechner's law]] is a good fit to [[loudness]] perception. However “[n]ot long after they had adopted the decibel scale for measuring sound intensities, the engineers noted that equal steps on the logarithmic (decibel) scale do not behave like equal steps [in sensation], for a level 50 db above threshold does not sound at all like half of 100 db, as [[Weber–Fechner law|Fechner's law]] implies it should.” (Stevens, 1957: 163). This led to the development of [[Stevens' power law]] which is generally found to be a better fit to data. [[Stanley Smith Stevens|Stevens]] (1957) suggested replacing the decibel scale with the [[Sone|sone scale]], but it did not seem to take root.

== Uses ==

=== Acoustics ===

The '''decibel''' unit is commonly used in acoustics to quantify [[sound]] levels relative to some 0 dB reference. Commonly, sound intensities are specified as a [[sound pressure level]] (SPL) relative to 20 micropascals (20 [[pascal (unit)|µPa]]) in gases and 1 µPa in other media (standardized in [[ANSI]] S1.1-1994).<ref name="SPL">[http://www.quietnoise.com/glossary.htm Glossary of Noise Terms] — ''Sound pressure level'' definition</ref> 20 µPa corresponds to the [[threshold of human hearing]] (roughly the sound of a [[mosquito]] flying 3 m away). Often, the unit ''dB(SPL)'' is used, implying the standard reference, though this is discouraged by the [[Acoustical Society of America]], which recommends explicitly stating the reference level for each measurement; "100 dB ''re'' 20 µPa". <ref name="rane">[http://www.rane.com/par-d.html#dB_SPL Rane Pro Audio Reference definition of "dB-SPL"]</ref><ref name="asacos">[http://asa.aip.org/standards/information/rules.pdf#page=17 ASACOS Rules for Preparation of American National Standards in Acoustics, Mechanical Vibration and Shock, Bioacoustics, and Noise]</ref>. In the remainder of this section, the reference level of 20&nbsp;µPa is implied.

A reason for using the decibel is that the [[ear]] is capable of detecting a very large range of [[sound pressure]]s. The ratio of the sound ''pressure'' that causes permanent damage from short exposure to the limit that (undamaged) ears can hear is above a [[million]]. Because the ''power'' in a sound wave is proportional to the ''square of the pressure'', the ratio of the maximum power to the minimum power is above one ([[long and short scales|short scale]]) [[trillion]]. To deal with such a range, logarithmic units are useful: the log of a trillion is 12, so this ratio represents a difference of 120 dB.

[[Psychologist]]s have debated whether [[loudness]] perception is better described as roughly logarithmic (see the [[Weber-Fechner law]]) or as a power law (see [[Stevens' power law]]), where the latter is now generally more accepted. A consequence of either model is that a volume control dial on a typical [[Electronic amplifier|audio amplifier]] that is labeled linearly in voltage amplification will affect the loudness much more for lower numbers than higher ones. This is why some are labeled in relation to decibels, i.e. the numbers are related to the logarithm of intensity.

Various [[frequency]] weightings are used to allow the result of an acoustical measurement to be expressed as a single sound level. The weightings approximate the changes in sensitivity of the ear to different frequencies at different levels. The two most commonly used weightings are the A and C weightings; other examples are the B and Z weightings.

In air, sound pressure levels above 85 dB are considered harmful, while 95 dB is considered unsafe for prolonged periods and 120 dB causes an immediate perforation of the ear drum (tympanic membrane). [[Window]]s break at about 163 dB. [[Jet aircraft]] cause A-weighted levels of about 133 dB at 33 m, or 100 dB at 170 m. In air at [[atmospheric pressure]], the simple relationship between pressure and power of a sound wave breaks down for pressures on the order of or greater than 1&nbsp;atmosphere, which corresponds to an SPL of 194 dB re 20 µPa (<math>20\log_{10}(1\ \mathrm{atm}/20\ \mu\mathrm{Pa})=194.09</math>). Waves with higher pressures are more properly called [[shock wave]]s rather than sound waves; their properties are very different properties from those of normal sound waves. One could extend the meaning of ''sound'' pressure level in order to describe the pressure waves emitted by processes such as earthquakes and explosions, and get numbers exceeding 194 dB, but these numbers should only be used if it is clear how the measurable quantities <!--don't change to pressure; the makeitlouder link uses total energy, wind speeds and so on--> are converted into SPL. An extensive list can be found at [http://www.makeitlouder.com/Decibel%20Level%20Chart.txt makeitlouder.com].

{| class="wikitable"

!dB(SPL)!!Source (with distance)

|-

|200 || Theoretical limit for a sound wave at 1 atmosphere environmental pressure

|-

|190 || Nuclear bomb explosion

|-

|180 ||[[Krakatoa]] explosion at 100 miles (160&nbsp;km) in air [http://www.makeitlouder.com/Decibel%20Level%20Chart.txt]

|-

|170 ||[[Firecracker]] in human hand

|-

|160 ||[[M1 Garand]] being fired at 1 meter (3.3 ft)

|-

|150 ||[[Jet engine]] at 30 [[metre|m]] (100 ft)

|-

|140 ||[[Rifle]] being fired at 1 m (3.3 ft)

|-

|130 ||[[Threshold of pain]]; civil defense siren at 33.3 m (100 ft)

|-

|120 ||[[Train horn]] at 1 m (3.3 ft)

|-

|110 ||[[Accelerating]] [[motorcycle]] at 5 m (16.5 ft) ; [[chainsaw]] at 1 m (3.3 ft)

|-

|100 ||[[Jackhammer]] at 2 m (6.5 ft); inside [[disco]]

|-

|90 ||[[Loud]] [[factory]], [[heavy]] [[truck]] at 1 m (3.3 ft)

|-

|80 ||[[Vacuum cleaner]] at 1 m (3.3 ft), [[curbside]] of busy [[street]]

|-

|70 ||Busy [[traffic]] at 5 m (16.5 ft)

|-

|60 ||[[Office]] or [[restaurant]] [[inside]]

|-

|50 ||Quiet [[restaurant]] inside

|-

|40 ||Residential area at [[night]]

|-

|30 ||[[Theatre]], no [[talking]]

|-

|20 ||[[Whispering]]

|-

|10 ||[[Human]] [[breathing]] at 3 m (10 ft)

|-

|0 ||[[Threshold of human hearing]] (with [[healthy]] [[ears]]); sound of a [[mosquito]] flying 3 m (10 ft) away

|}

Note that the SPL emitted by an object changes with distance from the object. Commonly-quoted measurements of objects like [[jet engine]]s or [[jackhammer]]s are meaningless without distance information. The measurement is not of the object's noise, but of the noise at a point in the air near that object. For instance, it is intuitively obvious that the noise level of a [[volcanic eruption]] will be much higher standing inside the crater than it would be measured from 5 kilometers away.

Sound pressure levels are applicable only to the specific position at which they are measured. The levels change with the distance from the source of the sound; in general, the level decreases as the distance from the source increases. If the distance from the source is unknown, it is difficult to estimate the sound pressure level at the source. Measurements that refer to the "threshold of pain" or the threshold at which ear damage occurs are measuring the SPL at a point near the ear itself. Measurements of ambient noise do not need a distance, since the noise level will be relatively constant at any point in the area (and are usually only rough approximations anyway).

Under controlled conditions, in an acoustical laboratory, the trained healthy human ear is able to discern changes in sound levels of 1 dB, when exposed to steady, single frequency ("pure tone") signals in the mid-frequency range. It is widely accepted that the average [[health]]y ear, however, can barely perceive noise level changes of 3 dB.

On this scale, the normal range of human hearing extends from about 0&nbsp;dB(SPL) to about 140&nbsp;dB(SPL). 0&nbsp;dB(SPL) is the [[threshold of hearing]] in healthy, undamaged human ears at 1 kHz; 0&nbsp;dB(SPL) is not an absence of sound, and it is possible for people with exceptionally good hearing to hear sounds at −10&nbsp;dB(SPL). A 3 dB increase in the level of continuous noise doubles the sound power, however experimentation has determined that the response of the human ear results in a perceived doubling of loudness for approximately every 10 dB increase (part of [[Stevens' power law]]).

==== Frequency weighting ====

{{main|Frequency weighting}}

Since the human ear is not equally sensitive to all the frequencies of sound within the entire spectrum, noise levels at maximum human sensitivity — middle A and its higher [[harmonic]]s (between 2 and 4 [[hertz|kHz]]) — are factored more heavily into sound descriptions using a process called frequency weighting.

The most widely used frequency weighting is the "[[A-weighting]]", which roughly corresponds to the inverse of the 40 dB (at 1 kHz) equal-loudness curve. Using this filter, the sound level [[Measuring instrument|meter]] is less sensitive to very high and very low frequencies. The A weighting parallels the sensitivity of the human ear when it is exposed to normal levels, and frequency weighting C is suitable for use when the ear is exposed to higher sound levels. Other defined frequency weightings, such as B and Z, are rarely used.

Frequency weighted sound levels are still expressed in decibels (with unit symbol dB), although it is common to see the incorrect unit symbols dBA or dB(A) used for A-weighted sound levels. Performance characteristics for professional and consumer audio products are commonly measured with A-weighted filtering.

==== In water ====

For the same source pressure at 1 m, the underwater dB level will be higher by 62 dB, due to the difference in reference levels (20 µPa vs 1 µPa = 26.0 dB difference), and the difference in [[acoustic impedance]] between air and water (3600 times = 35.6 dB difference).<ref name="air to water">[http://www.fas.org/man/dod-101/sys/ship/acoustics.htm#conversion Air to Water conversion]</ref>

=== Electronics ===

The decibel is used rather than [[Arithmetic|arithmetic]] ratios or [[percent]]ages because when certain types of [[Electrical network|circuits]], such as amplifiers and [[attenuator]]s, are connected in series, expressions of power level in decibels may be arithmetically added and subtracted. It is also common in disciplines such as audio, in which the properties of the signal are best expressed in logarithms due to the response of the ear.

In [[radio]] electronics, the decibel is used to describe the ratio between two measurements of [[electrical power]]. It can also be combined with a suffix to create an absolute unit of electrical power. For example, it can be combined with "m" for "milliwatt" to produce the "[[dBm]]". Zero dBm is one milliwatt, and 1&nbsp;dBm is one decibel greater than 0&nbsp;dBm, or about 1.259&nbsp;mW.

Although decibels were originally used for power ratios, they are also used in electronics to describe voltage or current ratios. In a constant resistive load, power is proportional to the square of the voltage or current in the circuit. Therefore, the decibel ratio of two voltages ''V''₁ and ''V''₂ is defined as 20&nbsp;log₁₀(''V''₁/''V''₂), and similarly for current ratios. Thus, for example, a factor of 2.0 in voltage is equivalent to 6.02&nbsp;dB (not 3.01&nbsp;dB!). Similarly, a ratio of 10 times gives 20&nbsp;dB, and one tenth gives −20&nbsp;dB.

This practice is fully consistent with power-based decibels, provided the circuit [[Electrical resistance|resistance]] remains constant. However, voltage-based decibels are frequently used to express such quantities as the voltage gain of an amplifier, where the two voltages are measured in different circuits which may have very different resistances. For example, a unity-gain [[buffer amplifier]] with a high [[input resistance]] and a low [[output resistance]] may be said to have a "voltage gain of 0 dB", even though it is actually providing a considerable power gain when driving a low-resistance load.

In professional audio, a popular unit is the dBu (see below for all the units). The "u" stands for "unloaded", and was probably chosen to be similar to lowercase "v", as dBv was the older name for the same thing. It was changed to avoid confusion with dBV. This unit (dBu) is an [[root mean square|RMS]] measurement of voltage which uses as its reference 0.775&nbsp;V_RMS. Chosen for historical reasons, it is the voltage level at which you get 1&nbsp;mW of power in a 600&nbsp;ohm resistor, which used to be the standard impedance in almost all professional audio circuits. <!--what's a "professional audio circuit"?--> <!-- a circuit that uses 600 Ω for everything. :-) they mean stuff for professional audio like recording and live sound. microphones, mixers, etc. i think. -->

Since there may be many different bases for a measurement expressed in decibels, a dB value is considered an ''absolute'' measurement only if the reference value (equivalent to 0&nbsp;dB) is clearly stated. For example, the [[gain]] of an [[antenna (radio)|antenna]] system can only be given with respect to a reference antenna (generally a perfect [[Isotropic radiator|isotropic antenna]]); if the reference is not stated, the dB value is a ''relative'' measurement, such as the gain of an amplifier.

=== Optics ===

In an [[optical link]], if a known amount of [[Optics|optical]] power, in [[dBm]] (referenced to 1 mW), is launched into a [[Optical fiber|fibre]], and the losses, in dB (decibels), of each [[electronic component]] (e.g., connectors, splices, and lengths of fibre) are known, the overall link [[loss]] may be quickly calculated by simple addition and subtraction of decibel quantities.

=== Telecommunications ===

In telecommunications, decibels are commonly used to measure [[signal-to-noise ratio]]s and other ratio measurements.

Decibels are used to account for the gains and losses of a signal from a transmitter to a receiver through some medium (free space, wave guides, coax, fiber optics, etc.) using a [[Link Budget]].

=== Seismology ===

Earthquakes were formerly measured on the [[Richter magnitude scale|Richter scale]], which is expressed in bels. (The units in this case are always assumed, rather than explicit.) The more modern [[moment magnitude scale]] is designed to produce values comparable to those of the Richter scale.<!--but perhaps is unitless, since it is not based on a base 10 log of an amplitude-->

== Typical abbreviations ==

=== Absolute measurements ===

'''Electric power'''

:'''[[dBm]]''' or '''dBmW'''

::dB(1 mW) — power measurement relative to 1 milliwatt.

:'''[[dBW]]'''

::dB(1 W) — same as dBm, with reference level of 1 [[watt]].

'''Electric voltage'''

:'''dBu''' or '''dBv'''

::dB(0.775 V) — (usually [[root mean square|RMS]]) [[volt]]age [[amplitude]] referenced to 0.775 volt. Although dBu can be used with any impedance, dBu = dBm when the load is 600 Ω. dBu is preferable, since dBv is easily confused with dBV. The "u" comes from "unloaded".

:'''dBV'''

::dB(1 V) — (usually RMS) voltage amplitude of a signal in a [[wire]], relative to 1 volt, not related to any impedance.

'''Acoustics'''

:'''dB(SPL)'''

::dB(Sound Pressure Level) — relative to 20 micropascals (μPa) = 2×10⁻⁵ Pa, the quietest sound a human can hear.<ref name="SPL"/> This is roughly the sound of a mosquito flying 3 metres away. This is often abbreviated to just "dB", which gives some the erroneous notion that "dB" is an absolute unit by itself.

'''Radio power'''

:'''dBm'''

::dB(mW) — power relative to 1 [[milliwatt]].

:'''dBμ''' or '''dBu'''

:: dB(μV/m) — [[electric field strength]] relative to 1 [[microvolt]] per [[metre]].

:'''dBf'''

:: dB(fW) — power relative to 1 [[femtowatt]].

:'''dBW'''

:: dB(W) — power relative to 1 [[watt]].

:'''dBk'''

:: dB(kW) — power relative to 1 [[kilowatt]].

==== Note regarding absolute measurements ====

The term "measurement relative to" means so many dB greater than or less than the quantity specified.

Some examples:

*&nbsp;3&nbsp;dBm means 3&nbsp;dB greater than 1&nbsp;mW.

*−6&nbsp;dBm means 6&nbsp;dB less than 1&nbsp;mW.

*&nbsp;0&nbsp;dBm means no change from 1&nbsp;mW, in other words 0&nbsp;dBm ''is'' 1&nbsp;mW.

=== Relative measurements ===

; [[dB(A)|dB(A), dB(B), and dB(C)]] weighting : These symbols are often used to denote the use of different [[frequency weighting]]s, used to approximate the human ear's [[response]] to sound, although the measurement is still in dB (SPL). Other variations that may be seen are dB_A or dBA. According to ANSI standards, the preferred usage is to write L_A = x dB, as dBA implies a reference to an "A" unit, not an A-weighting. They are still used commonly as a shorthand for A-weighted measurements, however.

; dBd : dB(dipole) — the forward gain of an [[antenna (electronics)|antenna]] compared to a half-wave [[dipole]] antenna.

; dBi : dB(isotropic) — the forward gain of an antenna compared to an idealized [[isotropic]] antenna.

; [[dBFS]] ''or'' dBfs : dB([[full scale]]) — the [[amplitude]] of a signal (usually audio) compared to the maximum which a device can handle before [[clipping]] occurs. In digital systems, 0 dBFS would equal the highest level (number) the processor is capable of representing. This is an instantaneous (sample) value as compared to the dBm/dBu/dBv which are typically RMS.(Measured values are usually negative, since they should be less than the maximum.)

; dBr : dB(relative) — simply a relative difference to something else, which is made apparent in context. The difference of a filter's response to nominal levels, for instance.

; [[dBrn]] : dB above [[reference noise]] See also [[dBrnC]].

; [[dBc]] : dB relative to carrier — in [[telecommunication]]s, this indicates the relative levels of noise or sideband peak power, compared to the carrier power.

== Reckoning ==

Decibels are handy for mental calculation, because adding them is easier than multiplying ratios.

First, however, one has to be able to convert easily between ratios and decibels.

The most obvious way is to memorize the logs of small primes, but there are a few other tricks that can help.

=== Round numbers ===

The values of coins and banknotes are round numbers. The rules are:

#One is a round number

#Twice a round number is a round number: 2, 4, 8, 16, 32, 64

#Ten times a round number is a round number: 10, 100

#Half a round number is a round number: 50, 25, 12.5, 6.25

#The tenth of a round number is a round number: 5, 2.5, 1.25, 1.6, 3.2, 6.4

Now 6.25 and 6.4 are approximately equal to 6.3, so we don't care. Thus the round numbers between 1 and 10 are these:

Ratio 1 1.25 1.6 2 2.5 3.2 4 5 6.3 8 10

dB 0 1 2 3 4 5 6 7 8 9 10

This useful approximate table of logarithms is easily reconstructed or memorized.

=== The 4 → 6 energy rule ===

To one decimal place of precision, 4.x is 6.x in dB (energy).

Examples:

* 4.0 → 6.0 dB

* 4.3 → 6.3 dB

* 4.7 → 6.7 dB

=== The "789" rule ===

To one decimal place of precision, x → (½ x + 5.0 dB) for 7.0 ≤ x ≤ 10.

Examples:

* 7.0 → ½ 7.0 + 5.0 dB = 3.5 + 5.0 dB = 8.5 dB

* 7.5 → ½ 7.5 + 5.0 dB = 3.75 + 5.0 dB = 8.75 dB

* 8.2 → ½ 8.2 + 5.0 dB = 4.1 + 5.0 dB = 9.1 dB

* 9.9 → ½ 9.9 + 5.0 dB = 4.95 + 5.0 dB = 9.95 dB

* 10.0 → ½ 10.0 + 5.0 dB = 5.0 + 5.0 dB = 10 dB

=== −3 dB ≈ ½ power ===

A level difference of ±3 dB is roughly double/half power (equal to a ratio of 1.995). That is why it is commonly used as a marking on sound equipment and the like.

Another common sequence is 1, 2, 5, 10, 20, 50 ... . These [[preferred number]]s are very close to being equally spaced in terms of their logarithms. The actual values would be 1, 2.15, 4.64, 10 ... .

The conversion for decibels is often simplified to: "+3 dB means two times the power and 1.414 times the voltage", and "+6 dB means four times the power and two times the voltage ".

While this is accurate for many situations, it is not exact. As stated above, decibels are defined so that +10 dB means "ten times the power". From this, we calculate that +3 dB actually multiplies the power by 10^3/10. This is a power ratio of 1.9953 or about 0.25% different from the "times 2" power ratio that is sometimes assumed. A level difference of +6 dB is 3.9811, about 0.5% different from 4.

To contrive a more serious example, consider converting a large decibel figure into its linear ratio, for example 120 dB. The power ratio is correctly calculated as a ratio of 10¹² or one trillion. But if we use the assumption that 3 dB means "times 2", we would calculate a power ratio of 2^120/3 = 2⁴⁰ = 1.0995 × 10¹², giving a 10% error.

=== 6 dB per bit ===

In [[digital audio]] linear [[pulse-code modulation]], the first bit (least significant bit, or LSB) produces residual quantization noise (bearing little resemblance to the source signal) and each subsequent [[bit]] offered by the system doubles the (voltage) resolution, corresponding to a 6 dB ratio. So for instance, a 16-bit (linear) audio format offers 15 bits beyond the first, for a [[dynamic range]] (between quantization noise and clipping) of (15 × 6) = 90 dB, meaning that the maximum signal (see ''0 dBFS'', above) is 90 dB above the theoretical peak(s) of [[quantization noise]]. The negative impacts of quantization noise can be reduced by implementing [[dither]].

=== dB chart ===

As is clear from the above description, the dB level is a [[logarithmic]] way of expressing power ratios. The following tables are cheat-sheets that provide values for various dB ''power'' ratios.

===== Commonly used dB values =====

{| class="wikitable"

!dB level!!Ratio

|-

| −30 dB ||1/1000

|-

| −20 dB ||1/100

|-

| −10 dB ||1/10

|-

| −3 dB ||0.5 (approx.)

|-

|3 dB ||2 (approx.)

|-

|10 dB ||10

|-

|20 dB ||100

|-

|30 dB ||1000

|-

|}

===== Other dB values =====

{| class="wikitable"

!dB level!!Ratio

|-

| −9 dB ||1/8 (approx.)

|-

| −6 dB ||1/4 (approx.)

|-

| −1 dB ||0.8 (approx.)

|-

|1 dB ||1.25 (approx.)

|-

|6 dB ||4 (approx.)

|-

|9 dB ||8 (approx.)

|-

|}

== See also ==

*[[Equal-loudness contour]]

*[[ITU-R 468 noise weighting]]

*[[Noise (environmental)]]

*[[Signal noise]]

*[[Sound pressure level]]

*[[Weighting filter]] — discussion of '''dBA'''

== References ==

<references/>

*Martin, W. H., "DeciBel — The New Name for the Transmission Unit", ''Bell System Technical Journal'', January 1929.

*Stevens, S. S. (1957). On the psychophysical law. ''Psychological Review'' 64(3):153—181. PMID 13441853.

== External links ==

*[http://www.phys.unsw.edu.au/~jw/dB.html What is a decibel?]

*[http://www.sizes.com/units/decibel.htm Description of some abbreviations]

*[http://www.osha.gov/pls/oshaweb/owadisp.show_document?p_table=STANDARDS&p_id=9735 Noise Measurement OSHA 1]

*[http://www.environmental-center.com/articles/article138/article138.htm Noise Measurement OSHA 2]

*[http://www.jimprice.com/prosound/db.htm Understanding dB]

*[http://www.rane.com/par-d.html#decibel Rane Professional Audio Reference entry for "decibel"]

*[http://hyperphysics.phy-astr.gsu.edu/hbase/sound/db.html#c1 Hyperphysics description of decibels]

*[http://www.makeitlouder.com/Decibel%20Level%20Chart.txt Decibel chart]

=== Converters ===

*[http://www.analog.com/Analog_Root/static/techSupport/designTools/interactiveTools/dbconvert/dbconvert.html V_peak, V_RMS, Power, dBm, dBu, dBV converter]

*[http://www.sengpielaudio.com/calculator-db-volt.htm Conversion: dBu to volts, dBV to volts, and volts to dBu, and dBV]

*[http://www.sengpielaudio.com/calculator-soundlevel.htm Conversion of sound level units: dBSPL or dBA to sound pressure p and sound intensity J]

*[http://www.sengpielaudio.com/calculator-volt.htm Conversion: Voltage V to dB, dBu, dBV, and dBm]

*[http://www.moonblinkwifi.com/dbm_to_watt_conversion.cfm Only Power: dBm to mW conversion]

[[Category:Units of measure]]

[[Category:Sound]]

[[Category:Acoustics]]

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