Acoustic Symbols
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)
