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Sound pressure or acoustic pressure is the local pressure deviation from the ambient (average or equilibrium) atmospheric pressure, caused by a sound wave. In air, sound pressure can be measured using a microphone , and in water with a hydrophone .
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]
In reality, dimensionless point sources and one-dimensional line sources cannot exist; however, calculations can be made based on these theoretical models for simplicity. Thus there is only a certain distance where a line source of a finite length will produce a sound pressure higher than an equally loud point source.
An equal-loudness contour is a measure of sound pressure level, over the frequency spectrum, for which a listener perceives a constant loudness when presented with pure steady tones. [1] The unit of measurement for loudness levels is the phon and is arrived at by reference to equal-loudness contours. By definition, two sine waves of differing ...
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 ...
p is the acoustic pressure in the medium; ρ is the volumetric mass density of the medium; c is the speed of the sound waves traveling in the medium; δ is the particle displacement; x is the space variable along the direction of propagation of the sound waves. This equation is valid both for fluids and solids. In fluids, ρc 2 = K (K stands ...
The centimeter-gram-second system of units, the reference sound pressure for measuring ambient noise level is 0.0002 dyn/cm 2, or 0.00002 N/m 2. [6] Most frequently ambient noise levels are measured using a frequency weighting filter, the most common being the A-weighting scale, such that resulting measurements are denoted dB(A), or decibels on ...
The horizontal axis shows frequency in Hertz. In acoustics, loudness is the subjective perception of sound pressure.More formally, it is defined as the "attribute of auditory sensation in terms of which sounds can be ordered on a scale extending from quiet to loud". [1]