Eigenmodes
The nature of the terminations at the input and output of a wave guide influence the eigenmodes of an acoustical system.
A eigenmode characterises an oscillating system by a eigenfrequency and a mode shape.
The eigenfrequency is one of the resonant frequencies of the system, for which a tiny quantity of applied energy will cause oscillation of the system.
The mode shape is the spatial repartition of the physical quantities (pressure, volume velocity) at this frequency.
Illustrated examples of the natural frequencies and mode shapes are given in references [6] and [7].
