The technology inside hearing aids also differs. Hearing aid electronics control how sound is transferred from the environment to your inner ear. All hearing aids amplify sounds, making them louder so that you can hear them better. But various technologies do this differently, including:

• Basic analog. This conventional technology amplifies all sounds equally. Your audiologist sets the amplification level, though it can be adjusted later. Loud sounds might require you to manually turn down the volume on your hearing aid. This type of technology is best for people who do most of their communicating in relatively quiet situations. Basic analog is the least expensive technology. Analog hearing aids are slowly being phased out. Some companies make only digital hearing aids.
• Programmable analog. The programmability of this technology means your audiologist can adjust these aids to amplify sounds differently. Softer sounds can be amplified more, and loud sounds can be amplified less or not at all. If you have this type of technology in your hearing aid, you might not need to adjust the volume in loud situations, as you would with basic analog electronics. Some of the programmable analog hearing aids allow you to have multiple settings. This may allow you to switch settings according to your situation, which can be done with a remote control or by pushing a small button on the hearing aid. These aids are being replaced by more flexible digital instruments.
• Digital. With this type of technology, a computer chip converts the incoming sound into digital code, then analyzes and adjusts the sound based on your hearing loss and listening needs. The signals are then converted back into sound waves and delivered to your ears. The result is sound that's more finely tuned to your hearing loss. Digital hearing aids are available in all styles, and the price you pay will depend on the features you choose. More advanced digital signal processing capabilities tend to translate into higher cost. If price is a concern, let your audiologist know and choose the best combination of features in your price range.

(by sicologic.com)