Posterior gap [1]

During breathing, the vocal cords are apart forming a V shape. When the vocal cords are transitioning from the breathing, V-shape, toward a parallel position, but they stop short of complete closure, this leaves a posterior gap. One example of this type of a posterior gap is from muscle tension, where the opening muscles (PCA) partially tighten during phonation competing with the closing muscles (LCA) and hold the cords slightly apart, allowing air to escape between the posterior portion of the vocal cords.

Arrows point to the gap remaining between the vocal processes when there is incomplete closure.

[2]

Arrows lie along the direction of closure and point to the gap remaining between the vocal processes when there is incomplete closure.

There are other causes for incomplete closure of the vocal processes leading to a posterior gap. One or both LCA muscles may be weak. There may be a mass preventing closure. In an individual with huskiness, it will be important to view the posterior configuration of the vocal cords.

Summary

A posterior gap allows air to leak

muscle tension is one cause of a posterior gap
there are other causes of posterior gaps
the size of a posterior gap will correspond with a commensurate degree of huskiness