Hearing transmission or nyen gyü (Tib. སྙན་བརྒྱུད་, Wyl. snyan brgyud), also sometimes translated as 'oral transmission' or 'whispered lineage', generally refers to the oral transmission of a teaching from one master to one student. The term emphasises orality and secrecy as it is generally, at least in the early stages of transmission, given one to one.
It is also a type of terma transmission and one of the seven authoritative transmissions. For example, Jamyang Khyentse Wangpo received seven cycles of hearing transmission revelations such as Yamantaka: Hearing Transmission, Mamo: Hearing Transmission, Vajrakilaya: Hearing Transmission. They are called ‘hearing transmissions’ because Jamyang Khyentse Wangpo received them by hearing teachings. Khyentse Wangpo saw the yidam deity face-to-face, and the yidam then spoke the words of the sadhanas, tantras and specific practical instructions which Khyentse Wangpo heard with his own ears. Therefore this is known as the ‘hearing’ transmission.