In general, digital technology offers the most flexibility and more options to address user comfort and speech intelligibility. There are additional types of technologies also available that, in most cases, can be incorporated into any size of hearing instrument.
A digital circuit is the most advanced circuit available. This circuit is programmed through a computer and usually has at least two channels. Each channel in a digital circuit is controlled independently of the others, and controls a certain range of pitches coming into the hearing instrument. This circuit has fine tuning ability to match individual hearing requirements and filter out certain unwanted sounds. Sounds are processed digitally which should result in a clearer signal versus analog circuitry. Another advantage of some digital circuits is that they analyze surrounding sounds to maximize soft speech-like sounds, while minimizing louder steady state noises, such as traffic or wind.
Directional technology utilizes microphones to determine which sounds are desirable, based on the direction from which they are coming. Usually hearing aids with directional capability can function in an omnidirectional mode (using just one microphone) to allow sounds coming from all directions. These devices can also function in the directional mode, which will attenuate sounds coming from the undesirable direction. The advantage of directional hearing aids is that unwanted sounds coming from a certain direction are reduced such as background noise coming from behind.
Compression addresses the need to provide a comfortable range of amplified hearing, particularly for loud sounds. In trying to make soft and average sounds loud enough to be heard, loud sounds may become uncomfortably harsh and loud. Compression technology limits the amount of amplification at certain levels, making the listening experience more comfortable for the hearing aid user.