While listening to the lungs with a stethoscope, the patient is asked to say the letter "e." What is heard is a higher pitched sound that sounds like the letter "a." (Some doctors refer to this as "e to a changes.") Most commonly, this indicates pneumonia.
Similar terms are bronchophony and whispered pectoriloquy. The mechanism is the same: fluid or consolidation causes the sound of the voice to be transmitted loudly to the periphery of the lungs where it is usually not heard.
Egophony comes from the Greek word for "goat," (aix, aig-) in reference to the bleating quality of the sound.