Acoustics Symbols

A-Z list of symbols commonly used within acoustics.

α


αE


A


AG


b


b(θ, ϕ)


B


BL


ℬ


ℬT


c


cg


cp

C


C‚Ñò


c‚Ñò


Cv


cV


CNEL


d


d’


D


DI


DNL


DT


e


E


Ek


Ep


EL


ℰ


ℰi


f


fr


fu, fi


F


Fe


g


G


h


H(θ, ϕ)


H(Tk)


I


Iref


I(t)


IIC


IL


ISL


‚Ñê


k


kB


kc ,km


‚Ñì


L


LA


LC


Ld


Ldn


Le


Leq


Lex


LEPN


Lh


Li


LN


Ln


LTPN


Lx


LNP


m


mr


M


ℳ


ℳℒ


ℳref


N


NCB


NEF


NL


NR


NSL


p


P


Pe


Pref


PR


Pr


PSL


PTS


q


Q


r


rt


rs


R


Re


·πò


Rm


Rr


RI


RII


RL


ROC


‚Ñõ


s


sL


S


SA, SB


SENEL


SIL


SL


SPL


SS


SSL


STC


Sv


SWR


T


TI


Tk


Tem, Tme


T‚àè


TL


TNI


TS


TSR


TTS


u


U


Ue


V


VL


Vref


w


W


x


X


Xm


Xr


y


Y


z


Z


Zm


Zr


α


β


γ


δ


η


ηB


ηe


θ


Θ


κ


λ


Γ


ξ


Ξ


Π


Πi


ρ


ρ0


ρL


ρS


σ


σS


τ


ϕ


Φ


ω


ω0


ωd


ωu, ωl


Ω


Ωeff


δ(υ)


δnm


1(υ)


acceleration; absorption coefficient (dB per distance); Sabine absorptivity


random-incidence energy absorption coefficient


sound absorption


array gain


loss per bounce; decay parameter


beam pattern


magnetic field; susceptance


bottom loss


adiabatic bulk modulus


isothermal bulk modulus


speed of sound


group speed


phase speed


electrical capacitance; acoustic compliance; heat capacity


heat capacity at constant pressure


specific heat at constant pressure


heat capacity at constant volume


specific heat at constant volume


community noise equivalent level (dBA)


detection index


detectability index


directivity; dipole strength


directivity index


detected noise level


detection threshold


specific energy


total energy


kinetic energy


potential energy


echo level


time-averaged energy density


instantaneous energy density


instantaneous force; frequency (Hz)


resonance frequency


upper, lower half-power frequencies


peak force amplitude; frequency (kHz)


effective force amplitude


spectral density of a transient function; sound-speed gradient; acceleration of gravity


conductance


specific enthalpy


directional factor


population function


time-averaged acoustic intensity; current, effective current amplitude


reference acoustic intensity


instantaneous acoustic intensity


impact isolation class


intensity level


intensity spectrum level


impulse


wave number


Boltzmann’s constant


coupling coefficients


discontinuity distance


inductance


A-weighted sound level (dBA)


C-weighted sound level (dBC)


daytime average sound level (dBA)


day-night averaged sound level (dBA)


evening average sound level (dBA)


equivalent continuous sound level (dBA)


noise exposure level (dBA)


effective perceived noise level


hourly average sound level (dBA)


intensity level re 10 ‾¹² W/m²


loudness level (phon)


night average sound level (dBA)


tone-corrected perceived noise level


x-percentile-exceeded sound level (dBA, fast)


noise pollution level (dBA)


mass


radiation mass


acoustic inertance; bending moment; molecular weight; acoustic Mach number


microphone sensitivity


microphone sensitivity level


reference microphone sensitivity


loudness (sone)


balanced noise criterion curves


noise exposure forecast


noise level


noise reduction


noise spectrum level


acoustic pressure


peak acoustic pressure amplitude


effective acoustic pressure amplitude


reference effective acoustic pressure amplitude


privacy rating


Prandtl number


pressure spectrum level


permanent threshold shift


charge; source strength density; thermal energy; scaled acoustic pressure (p/p0c²)


quality factor; source strength (amplitude of volume velocity)


specific gas constant; characteristic acoustic impedance; specific acoustic resistance


transition range


skip distance


resistance (acoustic, electrical, mechanical); reflection coefficient; radius of curvature


Reynolds number


range rate


mechanical resistance


radiation resistance


intensity reflection coefficient


power reflection coefficient


reverberation level


receiver operating characteristic


universal gas constant spring constant; condensation


spring constant; condensation


apparent source level


cross-sectional area; surface area; salinity


scattering strengths per unit area


single event noise exposure level Lex (dBA)


speech interference level


source level


sound pressure level


sea state


source spectrum level


sound transmission class


scattering strength per unit volume


standing wave ratio


period of motion; temperature; tension; transmission coefficient; reverberation time


intensity transmission coefficient


temperature in kelvin


transduction coefficients


power transmission coefficient


transmission loss


traffic noise index (dBA)


target strength


target strength for reverberation


temporary threshold shift


particle speed


peak particle velocity amplitude; volume velocity


effective particle velocity amplitude


volume; voltage; effective voltage amplitude; volume displacement


voltage level; voice level (dBA)


reference effective voltage amplitude


angular frequency; bandwidth


explosive yield


specific acoustic reactance


electrical reactance


mechanical reactance


radiation reactance


transverse displacement


admittance; Young’s modulus


specific acoustic impedance


impedance (acoustic, electrical, mechanical)


mechanical impedance


radiation impedance


spatial absorption coefficient


temporal absorption coefficient; one-half the flair constant; a nonlinearity coefficient


ratio of heat capacities; attenuation coefficient; a nonlinearity coefficient


boundary layer thickness; skin depth


coefficient of shear viscosity; efficiency


coefficient of bulk viscosity


effective coefficient of viscosity


incidence angle; phase angle; grazing angle; horizontal beam width; elevation angle


phase angle of impedance


thermal conductivity; radius of gyration; transverse component of the propagation vector


wavelength


co times the eikonal; Goldberg number


longitudinal particle displacement


amplitude of ξ


time-averaged power


instantaneous power


instantaneous density (kg/m³); probability density function


equilibrium density


linear density (kg/m)


surface density (kg/m²)


Poisson’s ratio; standard deviation; extinction cross section


scattering cross section


relaxation time; pulse duration; processing time


transformation factor; phase angle; torsion angle; turns ratio; inverse turns ratio


velocity potential


angular frequency (rad/s)


natural angular frequency


damped angular frequency


upper, lower half-power angular frequencies


solid angle


effective solid angle


Dirac delta function of argument υ


Kronecker delta


Heaviside unit function of argument υ (unit step function)