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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 .
The equation describes the evolution of acoustic pressure p or particle velocity u as a function of position x and time t. A simplified (scalar) form of the equation describes acoustic waves in only one spatial dimension, while a more general form describes waves in three dimensions.
The speed of sound (i.e., the longitudinal motion of wavefronts) is related to frequency and wavelength of a wave by =.. This is different from the particle velocity , which refers to the motion of molecules in the medium due to the sound, and relates to the plane wave pressure to the fluid density and sound speed by =.
Transmission loss in underwater acoustics describes the decrease of sound intensity that is reduced by a bubble curtain or other damping structure at a given frequency. The same term is sometimes used to mean propagation loss , which is a measure of the reduction in sound intensity between the sound source and a receiver, defined as the ...
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 ...
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]
The speed of sound in seawater depends on pressure (hence depth), temperature (a change of 1 °C ~ 4 m/s), and salinity (a change of 1‰ ~ 1 m/s), and empirical equations have been derived to accurately calculate the speed of sound from these variables. [25] [26] Other factors affecting the speed of sound are minor. Since in most ocean regions ...
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."