A grossly simplified explanation, but you get the drift. The first benefit of using two hearing aids is improved hearing in a noisy environment. Remember, even those with normal' hearing in both ears have difficulty understanding the people they're with in places such as a restaurant or bar. This could be potentially embarrassing in a social or business setting, if you do not acknowledge a person speaking to you on your unaided side. Another factor to consider is that wearing two hearing aids improves sound quality.
Binaural hearing requires less volume, which makes listening more comfortable and less tiring.
Secondly, with messages being sent to both ears, the brain is capable of hearing things in stereo'. This gives the listener a natural, balanced 3-D' sound which can be understood more clearly. A third advantage to binaural listening, is an enhanced ability to localize' a sound source. In other words, if hearing is not balanced between two ears, it becomes very difficult to determine the source of the sound. Finally, research suggests that monaural users may suffer from a phenomenon called adult onset auditory deprivation'.