Description: Not all hearing loss is located within the cochlea, in the organ of hearing. The synapses, which are connection points between sensory cells in the cochlea and the nerve fibers poised to take the information to the brain, can also wear out or incur damage. This auditory deficit is still under study in humans, but one of the proposed symptoms is difficulty hearing in noisy environments even though hearing (as defined by a conventional hearing test) is often normal or near-normal. By testing how hearing-nerve fibers convey sound information to the brain, we can identify ears suspected of synaptopathy, or hidden hearing loss. This damage to the synapses seems to develop slowly over time and does not require exposure to loud sounds.