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dBc (decibels relative to the carrier) is the power ratio of a signal to a carrier signal, expressed in decibels.For example, phase noise is expressed in dBc/Hz at a given frequency offset from the carrier. dBc can also be used as a measurement of Spurious-Free Dynamic Range between the desired signal and unwanted spurious outputs resulting from the use of signal converters such as a digital ...
A-weighted decibels are abbreviated dB(A) or dBA. When acoustic ( calibrated microphone) measurements are being referred to, then the units used will be dB SPL ( sound pressure level ) referenced to 20 micropascals = 0 dB SPL.
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 ...
The results have been used to develop NRR (SNR). When developing method No. 2, the authors used the available information about the characteristic noise in industry, in the US in the early 1950s, [53] and the difference in the noise levels (dBC and dBA) to take into account its spectrum – as in the HML method later.
A graph of the A-, B-, C- and D-weightings across the frequency range 10 Hz – 20 kHz Video illustrating A-weighting by analyzing a sine sweep (contains audio). A-weighting is a form of frequency weighting and the most commonly used of a family of curves defined in the International standard IEC 61672:2003 and various national standards relating to the measurement of sound pressure level. [1]
DBA statements are often used in conjunction with a franchise. The franchisee will have a legal name under which it may sue and be sued, but will conduct business under the franchiser's brand name (which the public would recognize). A typical real-world example can be found in a well-known pricing mistake case, Donovan v.
The phrase "dB below full scale" has appeared in print since the 1950s, [27] [28] [29] and the term "dBFS" has been used since 1977. [30]Although the decibel (dB) is permitted for use alongside units of the International System of Units (SI), the dBFS is not.
For compliance purposes, readings with an ANSI Type 2 sound level meter and dosimeter are considered to have an accuracy of ±2 dBA, while a Type 1 instrument has an accuracy of ±1 dBA. A Type 2 meter is the minimum requirement by OSHA for noise measurements and is usually sufficient for general-purpose noise surveys.