Chanting the Mantra OM is a widely used practice in the Tantric Hatha Yoga lineage, to open the throat space and express yourself authentically.

You know you are low on Udana if you are feeling heavy and bogged down like gravity is too strong in you! Also if you are feeling restricted in your expression and your voice is shaky, or you are feeling unmotivated or void of inspiration it might be a good time to increase your Udana.

Udana is also the energy that moves spiritual energy, in the form of "Kundalini", up the spine.