Building Acoustics

List of symbols xiii

SYMBOL QUANTITY UNIT

Zm mechanical impedance N⋅s/m

Zn normalized impedance (to Z 0 ) 1

Zr radiation impedance N⋅s/m

Zs specific acoustic impedance Pa⋅s/m

Zw wall impedance (transmission impedance) Pa⋅s/m

Z 0 characteristic impedance for air Pa⋅s/m

α attenuation coefficient m-

α absorption factor 1

α'^ absorption exponent^1
β phase coefficient m-
δ phase angle radians
δ viscous skin depth m
ε perforation ratio 1
γxy coherence function 1
γ adiabatic constant 1
μ coefficient of viscosity kg/(m⋅s)
η loss factor 1
ηij coupling loss factor 1
φ angle radians
κ thermal conductivity watt/(m⋅K)
λ wavelength m
υ Poisson’s ratio 1
θ angle radians
ρ density kg/m^3
σ^2 variance
σ porosity, radiation factor 1
τ transmission factor 1
ω angular frequency radians/s
ζ damping ratio 1
Γ propagation coefficient m-
Λ characteristic viscous length m
Λ′ characteristic thermal length m

NOTE For a quantity X, Xˆsignifies the amplitude value, Xthe RMS-value and X the

modulus.