The term 'sound-detecting organ' is referring to the EAR, which is a three letter word. The EAR is an organ of the human body that is responsible for detecting sound waves and converting them into signals that the brain can interpret. It is made up of three parts: the outer EAR, the middle EAR, and the inner EAR. The outer EAR collects sound waves and directs them into the EAR canal, where they vibrate the eardrum. The middle EAR contains three tiny bones that amplify the vibrations and send them to the inner EAR. The inner EAR contains the cochlea, which is filled with fluid and lined with thousands of tiny hairs that convert the vibrations into electrical signals that are sent to the brain.