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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, also called the sound power density and the sound energy flux density. [2] The SI unit of intensity, which includes sound intensity, is the watt per square meter (W/m 2).
Historically, loudness was measured using an ear-balancing method with an audiometer in which the amplitude of a sine wave was adjusted by the user to equal the perceived loudness of the sound being evaluated. [6] Contemporary standards for measurement of loudness are based on the summation of energy in critical bands. [7]
In balanced audio systems, there are equal and opposite signals (difference-mode) in inputs, and any interference imposed on both leads will be subtracted, canceling out that interference (i.e., the common-mode). CMRR is a measure of a system's ability to ignore such interference and especially hum at its input.
Sound travels at about 1,100 feet per second (340 m/s), so a room 20 feet (6.1 m) long will have resonances from 27.5 Hz upwards. These resonant modes cause large peaks and dips in the sound level of a constant signal as the frequency of that signal varies from low to high.
Sound power or acoustic power is the rate at which sound energy is emitted, reflected, transmitted or received, per unit time. [1] It is defined [2] as "through a surface, the product of the sound pressure, and the component of the particle velocity, at a point on the surface in the direction normal to the surface, integrated over that surface."
The sound energy density level gives the ratio of a sound incidence as a sound energy value in comparison to the reference level of 1 pPa (= 10 −12 pascals). [2] It is a logarithmic measure of the ratio of two sound energy densities. The unit of the sound energy density level is the decibel (dB), a non-SI unit accepted for use with the SI ...
The ratio of the sound intensity that causes permanent damage during short exposure to that of the quietest sound that the ear can hear is equal to or greater than 1 trillion (10 12). [37] Such large measurement ranges are conveniently expressed in logarithmic scale : the base-10 logarithm of 10 12 is 12, which is expressed as a sound intensity ...
The commonly used reference sound exposure in air is [2] E 0 = 400 μ P a 2 ⋅ s . {\displaystyle E_{0}=400~\mathrm {\mu Pa^{2}\cdot s} .} The proper notations for sound exposure level using this reference are L W /(400 μPa 2 ⋅s) or L W (re 400 μPa 2 ⋅s) , but the notations dB SEL , dB(SEL) , dBSEL, or dB SEL are very common, even if ...