What is a sound beam or a sound column?
Well, technically it is a vibrating column of air that has its height and direction determined by the size of the glottal slit through which it passes. The glottal slit is the space between the vocal cords. This space between the vocal cords is made larger or smaller as the cords are adjusted for pitch with a specific length, width, and depth vibrating. As the pitch rises, part of the cords stop vibrating, and seal more. The air moves outward through this smaller space, and is shaped accordingly.
When the space is bigger with more of the cords vibrating, then the sound beam is larger in diameter, not as tall, and has a direction that leans towards the front of the mouth. As the space gets smaller and smaller with less cords vibrating, the air molecules set into motion are crowded together with the sound beam becoming smaller in diameter, taller, and with a direction that leans ever backwards towards the soft palate; moving up into the cavities of the head.
The healthy function of the sound beam – moving air column – is determined by the healthy function of the vocal cords. This process also includes the size and shape of vowel which does play a role in determining specific direction of the sound beam.
In general though, the sound beam direction is forward on low notes and progressively leans backward as the pitch rises; moving from under the hard palate as a sound and sensation for low notes travelling to the area of the soft palate and beyond for high notes!