Until the 1990's all hearing aids were analog. That is their circuits processed the sound using strictly analog technology rather than digital technology ... much the same way that an old phonograph record or audio tape stored its data as an analog signal.
Analog technology is still used in some hearing aids and can be suitable for some types of hearing losses. Analog hearing aids are typically cheaper than the newer digital (computer-like) technology. Analog aids don't typically have as many adjustments or settings, but if fit well, they can be a very good hearing aids.
Analog aids can be quite sophisticated and have many important features, so they may still be good options for many people with hearing loss.
Digital aids fall into two categories:
- Hybrid aids, which use digital technology for controlling the aid, but analog technology for actually processing the sound itself.
- Full digital aids, which use digital technology for both controlling the aid and for processing the sound itself.
Hybrid aids were common when digital technology first appeared, but are becoming less common (and may disappear) as full digital aids become more common place.
There is a lot of "hype" about digital aids, with the implication being that they represent a "miracle". It's true that they are "leading edge" and likely to be the future. They do offer some advantages, but "miracle" may be a bit of an exaggeration. It's important to not lose track of the fact that other features (such as directional microphones, or telecoils), may actually be more important than whether an aid is digital or analog.
Analog aids may still be very suitable solutions for many peoples' hearing aid needs.