a medical examination

check into thoroughly

to listen secretly to a private conversation

listen without permission

to become aware of (sound) with the ears; to be told, receive (information etc)

detect by perceiving sound

to examine, study, (something) carefully

check into thoroughly

(to pay attention in order) to hear

hear and pay attention

to hear (a person, conversation etc) without the knowledge of the speaker(s), deliberately or by chance

hear and pay attention

to inquire too curiously (into other people's affairs); prise

interfere in someone else's business