AUDIOLOGIST/RIE ROSSOUW/CENTURION GAUTENG

Hearing aids come in two main categories known as analog and digital. All hearing aids contain the following basic components: a microphone, which helps pick up environmental sounds and conversations; hearing amplifier circuitry, which strengthens and augments the sounds; a miniature speaker or transmitter, which delivers the amplified sound to the user’s ears; and the batteries for powering the above technology.

 

Analog hearing aids are the most basic variety of hearing aids. This type of hearing device simply amplifies all received sound waves, re-transmitting them in their raw form, just louder. Digital hearing devices, on the other hand, convert the received sound waves into digital signals using a sophisticated information processing microchip that is embedded within the amplifier circuitry - Digital Signal Processing (DSP).

 

The following are advantages of digital hearing devices

 

• Digital hearing devices are powerful and versatile. They are able to adapt to various auditory needs and environmental conditions according to the user’s needs.

 

• The microchip present in all digital hearing devices is capable of analyzing and processing the different sounds picked up by the microphone, which in turn, allows it to block out ambient noise in addition to offering a high level of whistle reduction. As a result, digital speech amplifiers significantly outperform analog hearing aids in noisy environments like concerts and crowded restaurants. This is known as gain processing, which lessens the background noise while increasing the sound of conversation.

 

• Digital hearing aids also have digital feedback reduction (DFR) and this technology is all about eliminating the annoying feedback (the whistling noise that all hearing aids make in certain situations) that is so common with analog models. Digital technology allows the instrument to determine when feedback is going to occur and then virtually cancels it out so that it isn't audible or annoying!

 

• The presence of the microchip also makes it possible to pre-program the hearing aids for a wide variety of environments and hearing needs. Digital hearing devices are becoming more intuitive these days, able to offer increasingly personalized hearing augmentation.

 

• The best way to determine if a digital instrument would benefit you is to speak with your hearing healthcare professional about issues specific to your hearing loss and your hearing aids. Your hearing healthcare professional can help determine if the advanced capabilities of digital hearing instruments can provide greater assistance to you

 

Gain Processing

 

One of the primary benefits associated with flexible gain-processing schemes is the potential for increased audibility of sounds of interest without discomfort resulting from high intensity sounds. While this is more generally a benefit of compression rather than digital processing per se, the greatly increased flexibility and control of compression processing provided by DSP--such as input signal-specific band dependence, greater numbers of channels, and kneepoints with lower compression thresholds--can lead to improved audibility with less clinician effort. Expansion, the opposite of compression, has also been introduced in digital hearing aids. This processing can lead to greater listener satisfaction by reducing the intensity of low-level environmental sounds and microphone noise that otherwise may have been annoying to the user.

 

Digital Feedback Reduction (DFR)

 

The most advanced feedback reduction schemes monitor for feedback while the listener is wearing the hearing aid. Moderate feedback is then reduced or eliminated through the use of a cancellation system or notch filtering. DFR can substantially benefit users who experience occasional feedback, such as that associated with jaw movement and close proximity to objects.

 

Digital Noise Reduction (DNR)

 

This processing is intended to reduce gain, either in the low frequencies or in specific bands, when steady-state signals (noise) are detected. Although research findings supporting the efficacy of DNR systems are mixed, they do indicate that the DNR can work to reduce annoyance and possibly improve speech recognition in the presence of non-fluctuating noise. DNR is sometimes advocated as complementary processing to directional microphones. While directional microphones can reduce the levels of background noise regardless of its temporal content, they are limited to reducing noise from behind or to the sides of the user.

 

Digital Speech Enhancement (DSE)

 

These systems act to increase the relative intensity of some segments of speech. Current DSE processing identifies and enhances speech based either on temporal, or more recently, spectral content. DSE in hearing aids is still relatively new, and its effectiveness is largely unknown. Directional Microphones and DSP The ability of directional hearing aids to improve the effective signal-to-noise ratio provided to the listener is now well established. In some cases, however, combining DSP with directional microphones can act to further enhance this benefit. In some hearing aids, DSP is used to calibrate microphones, control the shape of the directional pattern, automatically switch between directional and omnidirectional modes and through expansion, reduce additional circuit noise generated by directional microphones.

 

Digital Hearing Aids as Signal Generators

 

Since digital hearing aids have a DSP at their heart, they are able to generate--as well as to process--sound. Current digital hearing aids use this capability to perform loudness growth and threshold testing in order to obtain fitting information specific to an individual patient's ears in combination with a specific hearing aid. Sound levels also can be verified through the hearing aid once it is fit. This technology has the potential both to increase accuracy of hearing aid fittings and potentially streamline the fitting process by reducing the need for some external equipment.

 

Current digital hearing aids are certainly exciting, and the future possibilities are endless. Before long, digital hearing aids will replace their analog counterparts altogether. We must, however, present this technology to patients in an informative and educational manner. Like many other high-tech devices, high expectations often accompany digital hearing aids. Counselling patients about appropriate expectations will continue to be more--not less--important as technology continues to advance.

 

How do I choose the best digital hearing aid?

 

Digital hearing devices are definitely the best choice when it comes to personalized hearing aids. In addition to the pre-programmable microchip, digital hearing devices can be further customized depending on your individual preferences. For example, hearing aids come in different shapes and sizes, from visible behind the ear (BTE) models to 100 percent discreet completely in the (ear) canal styles. The different models make it easy to choose hearing aids that fit  a user’s particular requirements for comfort and discretion.