Hearing Aid Circuitry Options
There are four basic levels of circuitry sophistication available:
- Low-level analog hearing aids
- Advanced-level analog and multi-channel compression hearing aids
- Computer-programmable aids
- And hearing aids that use digital technology
Level I Product: Low-Level Analog Instruments
The standard analog hearing aid has linear amplification. These devices are the most basic form of hearing aid. They typically amplify both weak and strong speech sounds by the same amount (much like using a single magnifying glass).
When the volume control is increased to make soft speech audible, stronger sounds (such as background noise) are frequently over-amplified. Relative to other products, linear hearing aids sound more distorted.
Level II Product: Advanced-Level analog Instruments and Multi-Channel Compression Instruments
These hearing aids have compression circuits that automatically adjust the loud sounds coming into the hearing aid (AGC). Some also provide greater amounts of amplification for soft sounds, where hearing-impaired people have the most difficulty, and less amplification for loud sounds (K-amp). These circuits provide lower levels of distortion than do linear aids.
They provide good speech understanding in quiet listening situations and low levels of background noise (small groups). There may be two or three channels of different sounds. These hearing aids are not programmed by a computer, but they are more flexible than Level I products.
Level III Product: Computer-Programmable Instruments
These hearing aids have multi-channel capability and compression capability as in Level II instruments. However, they are programmed for the patient's hearing loss via computer. This gives the audiologist more fine-tuning capabilities.
They may have multiple memories the patient can select depending on the listening situation (restaurant, TV, telephone, music). They may adjust incoming sound automatically without a volume control. They are advantageous for progressive or fluctuating hearing losses because the hearing aid can be reprogrammed in the office.
These products have great flexibility and the latest analog technology. Dual microphones have shown to help in understanding of speech in noise.
Level IV Product: Digital Technology
These instruments are among the newest technology on the market. They tend to be more flexible without introducing distortion. These hearing aids are computers. They offer the advantages of a Level II product with less distortion. The best analogy to illustrate the enhanced sound quality provided by digital technology is to compare the high-fidelity sound from a CD recording to that from an audiocassette tape.
Feedback or whistling tends to be less of a problem in these devices. Dual microphones have been shown to help understanding of speech in noise. These hearing aids may have multiple memories, multiple channels or bands, and/or multiple microphones.
For specific information on the price ranges of these hearing aids, please consult your audiologist.