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The decibel (symbol: dB) is a relative unit of measurement equal to one tenth of a bel ( B ). It expresses the ratio of two values of a power or root-power quantity on a logarithmic scale. Two signals whose levels differ by one decibel have a power ratio of 10 1/10 (approximately 1.26) or root-power ratio of 10 1/20 (approximately 1.12 ).
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.
Most sound-level measurements will be made relative to this reference, meaning 1 Pa will equal an SPL of 94 dB. In other media, such as underwater, a reference level of 1 ÎĽPa is used. [9] These references are defined in ANSI S1.1-2013. [10] The main instrument for measuring sound levels in the environment is the sound level meter.
Sound exposure level—in decibels—is not much used in industrial noise measurement. Instead, the time-averaged value is used. This is the time average sound level or as it is usually called the 'equivalent continuous sound level' has the formal symbol L AT as described in paragraph 3,9 "Definitions" of IEC 61672-1 where many correct formal ...
Sound intensity, also known as acoustic intensity, is defined as the power carried by sound waves per unit area in a direction perpendicular to that area. The SI unit of intensity, which includes sound intensity, is the watt per square meter (W/m 2 ). One application is the noise measurement of sound intensity in the air at a listener's ...
Maximum sound power level (L WA) related to a portable air compressor. Regulations often specify a method for measurement [3] that integrates sound pressure over a surface enclosing the source. L WA specifies the power delivered to that surface in decibels relative to one picowatt. Devices (e.g., a vacuum cleaner) often have labeling ...
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