What You Need To Know About Hearing Aid Technology

Hearing aids are distinguished by their technology or circuitry. In the early days, hearing aid technology involved vacuum tubes, large heavy batteries, bulky receivers and cords. Today, miniature microchips, computerization, and digitized sound processing are used in hearing aid design. Here’s what you need to know about current technology.

Conventional Analog and Programmable Analog Hearing Aids: These aids amplify all sounds (speech and noise) in the same way. This 1970’s technology is the oldest available and least expensive. This technology was often rejected due to numerous frustrations including: discomfort in noise, voices sounded artificial, distortion and unnatural sound quality. Programmable analog aids are the same as conventional analog aids except a microchip allows computer programmed settings for different listening environments, i.e., telephone conversation, quiet conversation in your home, or noisy situations like a restaurant.

Digital Signal Processing Hearing (“DSP”) Aids: A digital hearing instrument contains an actual computer, or microprocessor. Digital hearing instruments convert incoming sounds into digital code, manipulate the code to suit the user, and re-convert the code into sound. The digital computer chip analyzes the sounds of your environment to determine if the sound is noise or speech, makes millions of calculations per second to incoming sound and yields amplified, distortion-free signals that are different for each individual user. Digital hearing aids automatically adjust volume control with little or no effort from the user. DSP aids provide management of loudness discomfort, automatic control of acoustic feedback (whistling sounds), and noise reduction. The noise reduction filtering is an amazing feature of DSP aids. Users can now hear and UNDERSTAND voices even in challanging listening environments. DSP aids truly recognize speech and filter it from background noise; then reduce the background noise while enhancing the voices you want to understand. Today, Over 70 % Of Hearing Aids Fit have Digital Signal Processing (DSP); This Is the New Standard.

Channels or bands: In a multi-band hearing aid, input sounds are divided into a number of separate bands, each of which is separately programmed and controlled. Intense loud input signals in one band will have only a minimal effect upon the amplification pattern in other bands since each is separately controlled. Audibility can be preserved.

/i//small_1.jpg Directional Microphones: One of the best ways to improve speech intelligibility in noisy environments is to use a directional microphone system in the hearing aid. These systems suppress sounds that arrive from the side and the rear, increasing the audibility of the desired speech signal relative to other sounds. A conventional hearing aid microphone (omni-directional) is equally sensitive to all incoming sounds, regardless of the direction of the sounds. No sounds are reduced in relation to others. Directional microphones are optimized to be less sensitive to sounds from a specific direction, often in such a way that they are more sensitive to sounds from the front than from behind.

Directional microphone systems can be designed in many different ways. A common feature is the use of several microphone inlets and subsequent signal processing to allow the system to distinguish among sounds from different directions. In that way, it is possible to emphasize sounds from the front over those from behind. A directional microphone system can consist of either one microphone with several inlets or of two electronically coupled microphones. There are advantages of both systems.

/i//small_2.jpg Directional microphone systems with a single microphone have proven their worth for many years but are restricted in functionality because they most often only reduce sounds from one specific direction.

Directional microphone systems with two microphones have a wider choice in signal processing but are technically more challenging. Mastering these technical challenges has made it possible to design, for example, an adaptive directional system that automatically assesses which direction noise comes from and reduces it.

Feedback Cancellation: Acoustic squeal with hearing aids occurs when some portion of the amplified sounds escapes from the ear canal, reaches the microphone o f the hearing aid, and gets re-amplified. The traditional solution has been to focus on the earmold, to try to seal the amplified sound within the ear canal. Electronic solutions have included reduction in the high frequency gain of the hearing aid when feedback is sensed. The problem is than when you “turn down” the hearing aid, audibility is also reduced. The best method is where feedback back be reduced electronically without reducing the gain. This requires a sensor circuit to continually detect and monitor feedback. A signal is created within the hearing aid which is opposite to the feedback frequencies, therefore canceling each out.

Noise Reduction: This is a program within the hearing aid processor that senses noise in the environment and then reduces the gain in the frequency where the noise is present. The digital circuit can do this since most noise is at a steady pitch, tone, and volume. Most speech is constantly changing in pitch, tone, and volume. This feature can maintain the loudness of speech while minimizing noise.

Telecoils: Telephone switch . Some hearing aids are made with an induction coil inside. You can switch from the normal microphone "on" setting to a "T" setting in order to hear better on the telephone. (You should know that all wired telephones produced today must be hearing aid compatible). In the "T" setting, environment sounds are eliminated, and you only pick up sound from the telephone. Furthermore, you can talk without your hearing aid "whisting" because the microphone of the hearing aid is turned off!

Tip: Programmable analog hearing aids are often called “Digitally Programmable” hearing aids. While this is technically accurate, this is an analog hearing aid and NOT current state-of-the-art technology. Just because the aid is set or adjusted on the computer does not mean it is a fully digital aid. A fully digital aid has a digital signal processing chip with a 100% digital amplifier. Don’t confuse a low price aid with a 100% DSP aid.

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