With its single-degree of freedom this one-mass model
cannot represent the mucosal wave (unless it is allowed a
rotational degree of freedom [16]). As a result,coupling to
the acoustic inertance of the vocal tract is essential to
create a condition where the tissue velocity and the
intraglottal pressure are in phase and hence initiate and
sustain oscillation. While the one-mass model is generally
not sufficient for research purposes,it is a useful instructive
tool for learning some of the fundamental principles of
self-sustained oscillation [3].