Types of Hearing Aids
There are three basic types of hearing aids.
Linear aids are the most basic and economical hearing aid. This hearing aid is completely manual. You have to manually adjust a volume control to suit the situation. Many hearing aids of this type use analog (non-digital) circuits.
Semi-automatic hearing aids will automatically reduce the volume of loud sounds. It is still manually adjusted for softer and medium sounds. Some of these aids are analog and some are digital.
Automatic hearing aids will adjust depending on the situation. If you are in a quiet room, it will increase its volume to improve speech reception. If you are in a noisy room, it will automatically reduce the volume to maintain comfort, reduce distortion and improve voice discrimination. Most of these hearing aids are digital.
How Technology can improve the way you hear.
Technological advancements have been accelerating in the last few years. We can now fit hearing losses more accurately and improve understanding to a higher degree of precision than ever before. Below is a brief description of some of these advances.
Digital reproduction of sound is a great improvement over analog hearing aids. Analog hearing aids use older technology such as is used in record players and cassette players. Digital hearing aids contain computer chips which convert audio signals into digital numeric codes. Depending on the model of hearing aid selected, the computer chips can perform complex processing of these codes such as automatically setting the volume, reducing background noise, and automatically reducing feedback. Digital hearing aids offer high precision and less distortion. Performance of digital hearing aids is akin to digital devices such as high-definition TVs, CD players and DVD players.
Digital Signal Processing (DSP)
Hearing instruments with Digital Signal Processing use computer based algorithms to automatically adjust the hearing aid. It can detect if the environment is too loud or speech is too soft and corrects itself accordingly. The most advanced DSPs can even recognize the difference between noise and speech. It will reduce the noise and enhance speech.
Most digital hearing aids are also programmable. The hearing aid is able to be programmed or set to the individual’s hearing loss via a computer. It does not have just one prescription like eyeglasses. If the hearing aid needs to be adjusted, a cord is connected to the aid and it is reprogrammed. This offers great flexibility, accuracy and access to many features.
Multi Memory Option
Much like eye-glasses may have two or three settings (bi-focal and tri-focal), digital programmable hearing aids may optionally have multiple memories to optimize the hearing aid to specific situations. For example, one memory could be optimized for normal environments and a second optimized for restaurants. To change the memory, the user simply depresses a button on the hearing aid. Some hearing aid models will even detect the environment you are in and automatically select the memory for you. Depending on the model, up to 4 memories may be available.
Most hearing aids use omni-directional microphones. Omni-directional means all directions are amplified by the same amount. This is similar to the way the normal human ear hears. However, most hearing impaired individuals loose ability to separate speech from noise. Hearing aids may optionally include a second microphone which will change the listening pattern from omni-directional to directional. In other words, the hearing aid will amplify signals from the front more than signals from behind. This is of great advantage when in a noisy situation such as restaurants where conversation is toward the front. This feature is selected manually on some models and is automatic on others. The most advanced models can automatically locate and track background noise as it moves.