Brahmari means "bee sound". It is an optional element of pranayama.
What is the difference between Brahmari and Ujaii? Ujaii occurs by partially closing the epiglottis to form a hissing sound. Brahmari occurs when the escape of air on exhalation is restricted in the larynx by the vocal chords coming together and making a hum like the sound of a bee.
The effects of the two techniques are similar. The main difference is the resonant vibration created by brahamari is deeper in the throat, which has a more stimulating effect in the upper body and head, particularly in the medulla oblongata.