Directional microphones in hearing aids have been shown to improve the user's ability to hear in background noise. Using this method, a microphone within the hearing aid can be manually or automatically directed towards the desired source. For more information go to: Adaptive Directional Microphone Technology and Hearing Aids: Theoretical and Clinical Implications (David Fabry 2005).
New technology also includes analyzing sound signals in multiple dimensions which allows them to be categorized into noise or desired sounds. A program within the hearing aid is then able to reduce unwanted noise with minimal impact on desired noise, such as speech and music.
One of the most recent advances and most successful has been the development of a hearing aid with wireless FM capabilities that is able to connect to a microphone placed near the source of the sound you desire. This is one of the most successful ways to focus on the person or people that you wish to communicate with while reducing the effects of unwanted noise.