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NOVA Acoustics

Acoustic Symbols

A-Z list of symbols commonly used within acoustics.

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

αE random-incidence energy absorption coefficient

A sound absorption

AG array gain

b loss per bounce; decay parameter

b(θ, ϕ) beam pattern

B magnetic field; susceptance

BL bottom loss

ℬ adiabatic bulk modulus

ℬT isothermal bulk modulus

c speed of sound

cg group speed

cp phase speed

C electrical capacitance; acoustic compliance; heat capacity

C‚Ñò heat capacity at constant pressure

c‚Ñò specific heat at constant pressure

Cv heat capacity at constant volume

cV specific heat at constant volume

CNEL community noise equivalent level (dBA)

d detection index

d’ detectability index

D directivity; dipole strength

DI directivity index

DNL detected noise level

DT detection threshold

e specific energy

E total energy

Ek kinetic energy

Ep potential energy

EL echo level

ℰ time-averaged energy density

ℰi instantaneous energy density

f instantaneous force; frequency (Hz)

fr beam pattern

fu,fi upper, lower half-power frequencies

F peak force amplitude; frequency (kHz)

fe effective force amplitude

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

G conductance

h beam pattern

H(θ, ϕ) directional factor

H(Tk) population function

I time-averaged acoustic intensity; current, effective current amplitude

Iref reference acoustic intensity

I(t) instantaneous acoustic intensity

IIC impact isolation class

IL intensity level

ISL intensity spectrum level

‚Ñê impulse

k wave number

kB Boltzmann’s constant

kc ,km reference acoustic intensity

‚Ñì discontinuity distance

L inductance

LA A-weighted sound level (dBA)

LC C-weighted sound level (dBC)

Ld daytime average sound level (dBA)

Ldn day-night averaged sound level (dBA)

Le evening average sound level (dBA)

Leq equivalent continuous sound level (dBA)

Lex noise exposure level (dBA)

LEPN effective perceived noise level

Lh hourly average sound level (dBA)

Li intensity level re 10 ‾¹² W/m²

LN loudness level (phon)

Ln loudness level (phon)

LTPN tone-corrected perceived noise level

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

LNP noise pollution level (dBA)

m mass

mr radiation mass

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

ℳ microphone sensitivity

ℳℒ microphone sensitivity level

ℳref reference microphone sensitivity

N loudness (sone)

NCB balanced noise criterion curves

NEF noise exposure forecast

NL noise level

NR noise reduction

NSl noise spectrum level

p acoustic pressure

P peak acoustic pressure amplitude

Pe effective acoustic pressure amplitude

Pref reference effective acoustic pressure amplitude

PR privacy rating

Pr Prandtl number

PSL pressure spectrum level

PTS permanent threshold shift

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

Q quality factor; source strength (amplitude of volume velocity)

r specific gas constant; characteristic acoustic impedance; specific acoustic resistance

rt transition range

rs skip distance

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

Re Reynolds number

·πò range rate

Rm mechanical resistance

Rr radiation resistance

RI intensity reflection coefficient

RII power reflection coefficient

RL reverberation level

ROC receiver operating characteristic

‚Ñõ universal gas constant spring constant; condensation

s spring constant; condensation

sL apparent source level

S cross-sectional area; surface area; salinity

SA,SB scattering strengths per unit area

SENEL single event noise exposure level Lex (dBA)

SIL speech interference level

SL source level

SPL sound pressure level

SS sea state

SSL source spectrum level

STC sound transmission class

NCB balanced noise criterion curves

Sv scattering strength per unit volume

SWR standing wave ratio

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

TI intensity transmission coefficient

Tk temperature in kelvin

Tm,Tme transduction coefficients

T‚àè power transmission coefficient

TL transmission loss

TNI traffic noise index (dBA)

TS‚R target strength

TTS temporary threshold shift

u particle speed

U‚e peak particle velocity amplitude; volume velocity

V volume; voltage; effective voltage amplitude; volume displacement

VL voltage level; voice level (dBA)

Vref reference effective voltage amplitude

w angular frequency; bandwidth

W explosive yield

x specific acoustic reactance

X electrical reactance

Xm mechanical reactance

Xr radiation reactance

y transverse displacement

Y admittance; Young’s modulus

z specific acoustic impedance

Z impedance (acoustic, electrical, mechanical)

Zr radiation impedance

α spatial absorption coefficient

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

γ ratio of heat capacities; attenuation coefficient; a nonlinearity coefficient

δ boundary layer thickness; skin depth

η coefficient of shear viscosity; efficiency

ηB coefficient of bulk viscosity

ηe effective coefficient of viscosity

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

Θ phase angle of impedance

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

Œa wavelength

Γ Co times the eikonal; Goldberg number

ξ longitudinal particle displacement

Ξ amplitude of ξ

Πi instantaneous power

ρ instantaneous density (kg/m³); probability density function

ρ0 equilibrium density

ρL linear density (kg/m)

ρS surface density (kg/m²)

σ Poisson’s ratio; standard deviation; extinction cross section

σS scattering cross section

œÉÑ relaxation time; pulse duration; processing time

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

Φ velocity potential

ω angular frequency (rad/s)

ω0 natural angular frequency

ωd damped angular frequency

ωu'ωl upper, lower half-power angular frequencies

Ω solid angle

Ωeff effective solid angle

δ(υ)Zr Dirac delta function of argument υ

δnm Kronecker delta

1(υ) Heaviside unit function of argument υ (unit step function)


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