The challenge of unilateral hearing loss
Unilateral hearing loss, as befits its name, refers to hearing loss in only one ear. The main causes of unilateral hearing loss are physical injury, acoustic neroma (a benign intracranial tumor), microtia (where one ear is underdeveloped), or disease (measles, meningitis, mumps, etc.). While this may sound like a minimal impairment compared to full hearing loss, it presents its own set of challenges. These are mostly associated with the difficulty of interpreting sound through only one mediumin other words, hearing in mono instead of stereo. Cover one of your own ears in a crowd, or in a situation where someone is speaking over background noise. Can you pick out where the speaker is, or differentiate the speech from the environment?These difficulties result in other common side effects, such as irritability, headaches, and nervous anxiety. Sufferers of unilateral hearing loss may choose to avoid social situations due to the difficulty of understanding and carrying on conversations.Two special hearing aids have been developed for those with UHL: contralateral routing of signals (CROS) hearing aids and bone anchored hearing aids (BAHA). The CROS hearing aid transfers sound from the ear with poorer hearing and transmits it to the hearing ear, usually via two behind-the-ear units with wired or wireless transmission. Hearing sounds from both sides helps the listener situate themselves in the environment more easily. BAHAs, on the other hand, use the conductive properties of bone to transfer sound and stimulate the hearing ear’s cochlea. While this cannot necessarily improve sound localization, it can reduce the head shadow (a term for the region where sound amplitude is limited because of the head).