Wikipedia
Diplacusis, also known as diplacusis binauralis or inter aural pitch difference (IPD) is a type of hearing disorder that is the perception of a single auditory stimulus as two separate sounds which may differ in pitch or in time. It is typically (though not exclusively) experienced as a secondary symptom of sensorineural hearing loss, although not all patients with sensory neural hearing loss may experience diplacusis or tinnitus. Onset is usually spontaneous and can occur at the time of an acoustic trauma or in the midst of an ear infection. Sufferers may experience the effect permanently, or it may resolve on its own. Treatment includes a full medical examination as well as an audiological examination that may explain the nature of the problem. If needed, amplification may relieve the symptoms of diplacusis. Therapy in helping the patient understand the cause of the symptom and tinnitus retraining may provide some relief. In at least some cases, amplification makes no difference and there is no treatment other than waiting for natural resolution.