# Acoustic Glossary

## Sound and Vibration Terms, Definitions, Units, Measurements ..

variable

absorption factor for sound power (symbol α):

acoustic impedance (symbol Za) : at a surface, the complex quotient of the average sound pressure ... over that surface by the sound volume flow rate ... through that surface

angular frequency (symbol ω) : ω = 2πf

angular wavenumber (symbol k) : k = ω/c

attenuation coefficient (symbol α) :

characteristic impedance of a medium (symbol Zc) : at a point in a non-dissipative medium and for a plane progressive wave, the quotient of the sound pressure ... by the component of the sound particle velocity ... in the direction of the wave propagation

density (symbol ρ) : ρ = m/V

dissipation factor for sound power (symbol δ, ψ):

equivalent absorption area of a surface or object (symbol A) :

frequency (symbol f) : f = 1/T

group speed of sound (symbol cg) : cg = dω/dk

logarithmic frequency interval (symbol G) : G = lb(f2/f1)

mechanical surface impedance (symbol Zm) : at a surface, the complex quotient of the total force on the surface by the component of the average sound particle velocity ... at the surface in the direction of the force

period duration (symbol T) : duration of one cycle of a periodic phenomenon

phase coefficient (symbol β) :

phase speed of sound (symbol c) : c = ω/k

propagation coefficient (symbol γ) :

reflection factor for sound power (symbol r) :

reverberation time (symbol Tn):

sound energy density (symbol w) : time-averaged sound energy in a given volume divided by that volume

sound exposure (symbol E) :

sound exposure level (symbol LE) :

sound intensity (symbol i) : i = p.v

sound particle acceleration (symbol a) : a = dv/dt

sound particle displacement (symbol δ) : instantaneous displacement of a particle in a medium from what would be its position in the absence of sound waves

sound particle velocity (symbol v,u) : v = dδ/dt

sound power (symbol P, Pa) : through a surface, 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

sound power level (symbol LW) :

sound pressure (symbol p) : difference between instantaneous total pressure and static pressure

sound pressure level (symbol Lp) :

sound reduction index (symbol R) :

sound volume velocity (symbol q) : surface integral of the normal component of the sound particle velocity ... over the cross-section (through which the sound propagates)

static pressure (symbol ps) : pressure that would exist in the absence of sound waves

time-averaged sound intensity (symbol I) :

transmission factor for sound power (symbol τ) :

wavelength (symbol λ) : for a sinusoidal wave and in a direction perpendicular to the wavefront, distance between two successive points where at a given instant the phase ... differs by 2 π

wavenumber (symbol σ) : σ = 1/λ

See also : EAV (exposure action value) : ELV (exposure limit value)
agtest1
check the weekly 'personal' noise exposure entry
LAA-weighted, sound level 9642
LA • A-weighted, sound level 9643
LAA-weighted, sound level 9656
LAA-weighted, sound level diams
LAA-weighted, sound level 9675
LAA-weighted, sound level 9679
LAA-weighted, sound level 9900
LAA-weighted, sound level bull
LAA-weighted, sound level 9744
LAA-weighted, sound level 9632
LAA-weighted, sound level 9633
LAA-weighted, sound level 9655
LAA-weighted, sound level 9826
LA : A-weighted, sound level 8900
LAA-weighted, sound level 8902

this is a standard p, line-height 1.4em with 4px margins top and bottom

this is a standard p, line-height 1.4em with 4px margins top and bottom

this is a standard br i.e. line-height 1.4em
this is a standard br i.e. line-height 1.4em

this is a standard br i.e. line-height 1.4em after a 0.3 line-height space
this is a standard br i.e. line-height 1.4em

End of agtest