Meaning. DBQ. Dave Brubeck Quartet (band) DBQ. Dove Brothers Quartet. showing only Slang/Internet Slang definitions (show all 8 definitions) Note: We have 11 other definitions for DBQ in our Acronym Attic. new search · The Document Based Question (DBQ) is an essay question given to students taking Advanced Placement exams in the history subjects. These history exams covering World, Europe, and US History all have a 90 minute DBQ section · Long story short, DBQ Essay or “Document Based Question” is an assigned academic paper which is part of the AP U.S. History exam (APUSH) set by the United States College Board. It requires a student’s knowledge of a certain topic with evidence from around 3 to 16 reliable sources
DBQ - Definition by AcronymFinder
The decibel symbol: dB is a relative unit of measurement corresponding to one tenth of a bel B, dbq meaning.
It is used to express the ratio of one value of a power or root-power quantity to another, on a logarithmic scale. A logarithmic quantity dbq meaning decibels is called a level. The unit is used to express a change in value e. In the latter case, the numeric value expresses the ratio of a value to a fixed reference value; when used in this way, the unit symbol is often suffixed with letter codes that indicate the reference value.
For example, for the reference value of 1 volta common suffix is " V " e. Two principal types of scaling of the decibel are in common use. When expressing a power ratio, it is defined as ten times the logarithm in base When expressing root-power quantities, a change in amplitude by a factor of 10 corresponds to a 20 dB change in level.
The decibel scales differ by a factor of two, dbq meaning, so that the related power and root-power levels change by the same value in linear systems, where power is proportional to the square of amplitude. The definition of the decibel originated in the measurement of transmission loss and power in telephony of the early 20th century in the Bell System in the United States. The bel was named in honor of Alexander Graham Bellbut the bel is seldom used.
Instead, the decibel is used for a wide variety of measurements in science and engineeringmost prominently in acousticselectronicsand control theory, dbq meaning. In electronics, dbq meaning, the dbq meaning of amplifiers, attenuation of dbq meaning, and signal-to-noise ratios are often expressed in decibels.
The decibel originates from methods used to quantify signal loss in telegraph and telephone circuits. The unit for loss was originally Miles of Standard Cable MSC. The standard telephone cable implied was "a cable having uniformly distributed resistance of 88 Ohms per loop-mile and uniformly distributed shunt capacitance of 0.
InBell Telephone Laboratories received favorable response to a new unit definition among members of the International Advisory Committee on Long Dbq meaning Telephony in Europe and replaced the MSC with the Dbq meaning Unit TU.
Inthe Bell system renamed the TU into the decibel, [8] being one tenth of a newly defined unit for the base logarithm of the power ratio. It was named the belin honor of the telecommunications pioneer Alexander Graham Bell. The naming and early definition of the decibel is described in the NBS Standard's Yearbook of [11]. Since the earliest days of the telephone, the need for a unit in which to measure the transmission efficiency of telephone facilities has been recognized.
The introduction of cable in afforded a stable basis for a convenient unit and the "mile of standard" cable came into general use shortly thereafter, dbq meaning. This unit was employed up to when a new unit was adopted as being more suitable for modern telephone work. The new transmission unit is widely used among the foreign telephone organizations dbq meaning recently it was termed the "decibel" at the suggestion of the International Advisory Committee on Long Distance Telephony, dbq meaning.
The decibel may be defined by the statement that two amounts of power differ by 1 decibel when they are in the ratio of 10 0. The number of transmission units expressing the ratio of any two powers is therefore ten times the common logarithm of that ratio. This method of designating the gain or loss of power in telephone circuits permits direct addition or subtraction of the units expressing the efficiency of different parts of the circuit InJ. Horton argued that the use of the decibel as a unit for quantities other than transmission loss led to confusion, and suggested the name logit for "standard magnitudes which combine by multiplication", to contrast with the name unit for "standard magnitudes which combine by addition".
In April dbq meaning, the International Committee for Weights and Measures CIPM considered a recommendation for the inclusion of the decibel in the International System of Units SIbut decided against the proposal. The IEC Standard defines the following quantities. Finally, the level of a quantity is the logarithm of the ratio of the value of that quantity to a reference value of the same kind of quantity.
The bel is rarely used either without a prefix or with SI unit prefixes other than deci ; it is preferred, for example, to use hundredths of a decibel rather than millibels. Thus, five one-thousandths of a bel would normally be written 0. The method of expressing a ratio as a level in decibels depends on whether the measured property is a power quantity or a root-power quantity ; see Power, dbq meaning, root-power, and field quantities for details.
When referring to dbq meaning of power quantities, a ratio can be expressed as a level in decibels by evaluating ten times the base logarithm of the ratio of the measured quantity to reference value. Thus, the ratio of P measured power to P 0 reference power is represented by L Pthat ratio expressed in decibels, [20] which is calculated using the formula: [21].
The base logarithm of the ratio of the two power quantities is the number of bels. The number of decibels is ten times the number of bels equivalently, a decibel is one-tenth of a bel. P and P 0 must measure the same type of quantity, dbq meaning, and have the same units before calculating the ratio. If P is greater than P 0 then L P is positive; if P is less than P 0 then L P is negative. Rearranging the above equation gives the following formula dbq meaning P in terms of P 0 and L P :.
When referring to measurements of root-power quantities, it is usual to consider the ratio of the squares of F measured and F dbq meaning reference, dbq meaning. This is because the definitions were originally formulated to give the same value for relative ratios for both power and root-power quantities.
Thus, the following definition is used:. Similarly, in electrical circuitsdissipated power is typically proportional to dbq meaning square of voltage or current when the impedance is constant. Taking voltage as an example, this leads to the equation for power gain level L G :. where V out is the root-mean-square rms output voltage, V in is the rms input voltage. A similar formula holds for current. The term root-power quantity is introduced by ISO Standard as a substitute of field quantity.
The term field quantity is deprecated by that standard and root-power is used throughout this article, dbq meaning. Although power and root-power quantities are different quantities, their respective levels are historically measured in the same units, typically decibels. A factor of 2 is introduced to make changes in the respective levels match under restricted conditions such as when the medium is linear and the same waveform is under consideration with changes in amplitude, or the medium impedance is linear and independent of both frequency and time.
This relies on the relationship. However, even in a linear system in which the power quantity is the product of two linearly related quantities e. voltage and currentif the impedance is frequency- or time-dependent, this relationship does not hold in general, for example if the energy spectrum of the waveform changes. For differences in level, the required relationship is relaxed from that above to one of proportionality i. must hold to allow the power level difference to be equal to the root-power level difference from power P dbq meaning and V 1 to P 2 and V 2.
An example might be an amplifier with unity voltage gain dbq meaning of load and frequency driving a load with a frequency-dependent impedance: the relative voltage gain of the amplifier is always 0 dB, but the dbq meaning gain depends on the changing spectral dbq meaning of the waveform being amplified. Frequency-dependent impedances may be analyzed by considering the quantities power spectral density and the dbq meaning root-power quantities via the Fourier transformdbq meaning, which allows elimination of the frequency dependence in the analysis by analyzing the system at each frequency independently.
Since logarithm differences measured in these units often represent power ratios and root-power ratios, values for both are shown below. The dbq meaning is traditionally used as a unit of logarithmic power ratio, while the neper is used for logarithmic root-power amplitude ratio. The unit dBW is often used to denote a ratio for which the reference is 1 W, and similarly dBm for a 1 mW reference point. A change in power ratio by a factor of 10 corresponds to a change in level of 10 dB.
More precisely, dbq meaning, the change is ± 3. Likewise, dbq meaning, a doubling or halving of the voltage, dbq meaning, and quadrupling or quartering of the power, is commonly described as 6 dB rather than ± 6. Should it be necessary to make the distinction, the number dbq meaning decibels is written with additional significant figures. Similarly, an increase of 6, dbq meaning.
The decibel is useful for representing large ratios and for dbq meaning representation of multiplied effects such as attenuation from multiple sources along a signal chain. Its application in systems with additive effects is less intuitive. The logarithmic scale nature of the decibel means that a very large range of ratios can be represented by a convenient number, in a manner similar to scientific notation.
This allows one to clearly visualize huge changes of some quantity. See Bode plot and Semi-log plot. For example, dB SPL may be clearer than "a trillion times more intense than the threshold of hearing".
For example:. However, according to its critics, the decibel creates confusion, obscures reasoning, is more related to the era of slide rules than to modern digital processing, and is cumbersome and difficult to interpret. However, the linear-scale units still simplify in the implied fraction, so that the results would be expressed in dB-Hz. According to Mitschke, [28] "The advantage of using a logarithmic measure is that in a transmission chain, there are many elements concatenated, and each has its own gain or attenuation.
To obtain the total, dbq meaning of decibel values is much more convenient than multiplication of the individual factors. if two machines each individually produce a sound pressure level of, say, 90 dB at a certain point, then when both are dbq meaning together we should expect the combined sound pressure level to increase to 93 dB, but certainly not to dB!
Addition on a logarithmic scale is called logarithmic additionand can be defined by taking exponentials to convert to a linear scale, dbq meaning, adding there, dbq meaning, and then taking logarithms to return. Attenuation constants, in topics such dbq meaning optical fiber communication and radio propagation path lossare often expressed as a fraction or ratio to distance of transmission, dbq meaning.
These quantities are to be manipulated obeying the rules of dimensional analysisdbq meaning, e. The human perception of the intensity of sound and light more nearly approximates the logarithm of intensity rather than a linear relationship see Weber—Fechner law dbq meaning, making the dB scale a useful measure.
The decibel is commonly used in acoustics as a unit of sound pressure level. The reference pressure for sound in air is set at the typical threshold of perception of an average human and there are common comparisons used to illustrate different levels of sound pressure. As sound pressure is a root-power quantity, the appropriate version of the unit definition is used:. where p rms is the root mean square of the measured sound pressure and p ref is the standard reference sound pressure of 20 micropascals in air or 1 micropascal in water.
Use of the decibel in underwater acoustics leads to confusion, in part because of this difference in reference value. The human ear has a large dynamic range in sound reception. The ratio of the sound intensity that causes permanent damage dbq meaning short exposure to that of the quietest sound that the ear can hear is equal to or greater than 1 trillion 10 Since the human ear is not equally sensitive to all sound frequencies, the acoustic power spectrum is modified by frequency weighting A-weighting being the most common standard to get the weighted acoustic power before converting to a sound level or noise level in decibels.
The decibel is used in telephony and audio, dbq meaning. Similarly to the use in acoustics, a frequency weighted power is often used. For audio noise measurements in electrical circuits, the weightings are called psophometric weightings.
In electronics, the decibel is often used to express power or amplitude ratios as for gains in preference to arithmetic ratios or percentages. One advantage is that the total decibel gain of a series of components such as amplifiers and attenuators can be calculated simply by summing dbq meaning decibel gains of the individual components, dbq meaning. Similarly, in telecommunications, decibels denote signal gain or loss from a transmitter to a receiver through some medium free spacewaveguidecoaxial cablefiber opticsetc.
Mullen APUSH Period 7 DBQ Review
, time: 15:18DBQ - What does DBQ stand for? The Free Dictionary
· dbq. Death by Question. A tactic used by the College Board to see how well you absorbed the teachings of a college-level (AP) History course taking For other uses, see Decibel (disambiguation). The decibel (symbol: dB) is a relative unit of measurement corresponding to one tenth of a bel (B). It is used to express the ratio of one value of a power or root-power quantity to another, on a logarithmic · The Document Based Question (DBQ) is an essay question given to students taking Advanced Placement exams in the history subjects. These history exams covering World, Europe, and US History all have a 90 minute DBQ section
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