1
general::
Easily audible and understandable. For example, They told us, loud and clear, what to do in an emergency, or You needn't repeat it? I hear you loud and clear. This expression gained currency in the military during World War II to acknowledge radio messages (I read you loud and clear) although it originated in the late 1800s.
American Heritage Idioms
2
general::
Phrase(s): loud and clear
clear and distinctly. (Originally said of radio reception that is heard clearly and distinctly.) • Tom: If I’ve told you once, I’ve told you a thousand times: Stop it! Do you hear me? Bill: Yes, loud and clear. • I hear you loud and clear.
McGrawhill's American Idioms And Phrasal Verbs