This level of technology is what we would term an advanced electronic instrument that is essentially linear in nature, in terms of processing but is programmed to the patients individual needs via digital programming. Examples of this technology are the RESOUND® hearing aid which was originally developed by AT&T Bell Labs and programmable SEQUEL® as developed by Starkey Labs.
Programmable circuit features allow the hearing instrument to be variably reset and adjusted (via an external computer platform and software) closely to the patients targeted needs. The advantages are the more precise acoustic adjustments that can be made when the product is fitted to the patient. More exact variable adjustments to individual patient preferences can be easily made while wearing (fitting) the aids during the fitting process and the patient can "test drive" different settings in various created environmental conditions (quiet, cafeteria noise, traffic, theater, groups at cocktail parties, etc.) Digitally programmable hearing aids are programmed and adjusted via a computer without having to be returned to the manufacturer, but because they process sound using linear electronics (analogue), they are not classified as 100% digital.
Obviously, programmable technology offers terrific flexibility and most of the products on the market have full menus of features available, including multi-channels, wide dynamic range compression, automatic signal processing, multiple and directional microphones, crossover frequency transition points, telephone features, remote controls (for dexterity problems), reverse slopes, etc. The primary bottom line advantages are: