Brahmari pranayama and is breathing that promotes inner peace and absorption in oneself.
Brahmari is

not only a breathing technique, but also the simplest meditation for beginner practitioners.
Brahmari is translated as “bee”. During its execution, we make a sound similar to the buzzing of a bee. The vibration generated during the practice calms the mind and the nervous system. This practice, unlike others, only indirectly controls prana, it is more of a meditative practice.

has a calming effect on the nervous system;
promotes the development of the vocal cords and the melody of the voice;
helps to get rid of insomnia;
lowers blood pressure;
relieves stress and tension;
promotes the treatment of throat diseases;
prepares for meditation by paying attention inward.
Sometimes Brahmari Pranayama is called “brain massage” because it allows you to feel a pleasant emptiness in your head.
It is recommended that you practice before bed to help you calm down and fall asleep easier.