Some individuals with normal hearing experience difficulties with hearing in adverse listening conditions, such as in noisy or reverberant environments or when listening to someone talking rapidly. In recent years, the term “hidden hearing loss” has been used to describe this type of hearing difficulty among individuals with hearing thresholds within normal limits (less than 25 dB HL). One physical cause of hidden hearing loss is thought to be “cochlear synaptopathy,” which refers to the damage of synaptic connections between inner hair cells and auditory nerve (AN) fibers. Research in animals has revealed evidence of cochlear synaptopathy following temporary hearing loss while outer hair cell (OHC) function remained intact. There is some debate in the literature on whether cochlear synaptopathy does occur in humans, and if it does, what its prevalence and consequences in terms of hearing in noise are. This is partly due to the difficulty in obtaining direct evidence of cochlear synaptopathy in living humans given that histological examination of fixated tissue is required. Importantly, clinical research on whether cochlear synaptopathy occurs in humans has been inconclusive. In addition to cochlear synaptopathy, research in humans and animals suggests that OHC function may also contribute to speech understanding in the presence of background noise.