CAD	Computer-Aided Design
CRC	Collaborative Research Center
CFD	Computational Fluid Dynamics
DOF	Degree of freedom
elPaSo	elementary Parallel Solver
FEM	Finite-Element Method
GUM	Guide to the Expression of Uncertainty in Measurement
PLA	Polyactic Acid
A	specimen cross-sectional area
$c_i$	sensitivity coefficient of ith input parameter
d	bar width
E	Young’s Modulus
h	layer height
$H_{12}$	transfer function between microphone 1 and microphone 2
j	imaginary unit $\left(\sqrt{-1}\right)$
k	wave number
l	specimen height
q	volume flow through the specimen
r	reflection factor
R	flow resistance
$R_S$	specific flow resistance
s	bar spacing
$u_c$	combined uncertainty
v	flow velocity through the specimen
x	axial coordinate in the impedance tube
$x_0$	microphone distance
$x_1$	distance from microphone 1 to the specimen
$x_i$	i-th input quantity
$\alpha$	absorption coefficient (superscripts: M, measured; C, computed)
${\alpha }_{\infty }$	tortuosity
$\Gamma \left(\dots \right)$	target function to be optimized
$\Delta p$	pressure drop over the specimen
$\eta$	damping coefficient
$\Lambda$	viscous characteristic length
${\Lambda }^{\prime }$	thermal characteristic length
$\nu$	Poisson’s ratio
${\rho }_F$	air density
${\rho }_S$	skeleton density
$\sigma$	flow resistivity
$\phi$	layer rotation angle
$\varphi$	porosity