The term 'Cochlea Setting' refers to the setting of the cochlea, which is a spiral-shaped cavity in the inner EAR. It is filled with fluid and lined with tiny hairs that vibrate when sound waves enter the EAR. This vibration is then converted into nerve impulses that are sent to the brain, allowing us to hear. The three-letter answer to this crossword puzzle is EAR, which stands for the organ of hearing.