Hearing aids have changed a lot over the past few decades but at their core, they have always been made of four basic parts: a microphone, a processor, a receiver and a power source. The microphone picks up the sounds in the wearer’s environment and passes it to the processor. The processor enhances the signal and delivers it to the receiver, which delivers the amplified signal to the ear canal. The power source, of course, drives the system. The digital age has transformed these four basic parts into four very sophisticated components. For example, virtually all hearing aids on the market today are digital, which means that the signal picked up by the microphone is converted from analog to digital before being processed, then converted back from digital to analog before the receiver delivers the enhanced signal into the ear canal.
The bulk of the technology that is packaged into a hearing aid resides in the part that is called the processor. The processors today are more programmable than ever before. This allows the hearing care professional to precisely fine-tune the amplification characteristics and customize other special features based on the individual needs of the wearer. The practitioner programs the hearing aids by connecting them to a computer and detecting them with special software provided by the hearing aid manufacturer. You can get almost any hearing aid processor tucked into whatever hearing aid style you prefer.
Hearing aid technology can be broadly divided into basic and advanced groups, based on the sophistication of features available in the processor. Even today’s basic digital hearing aids offer way more benefit to individuals with hearing loss than the best hearing aids of previous generations.
Basic hearing aid technology
Basic digital hearing aids generally require the wearer to make some manual adjustments in certain listening situations—such as turning a volume control up or down, or pushing a button on the aids in order to reduce noise coming from behind the wearer. The processor may separate incoming signals into two or more channels and process each channel separately. For example, a basic two-channel instrument may be programmed to give more amplification for high-frequency sounds than it gives for low-frequency sounds, in order to accommodate an individual’s hearing loss. Although programmable by computer, basic hearing aids generally have limited adjustments available for fine-tuning to fit unusual patterns of hearing loss. They are also less customizable and automated than hearing aids with advanced technology.
The following are examples of features that are usually included in basic hearing aid technology.
The number of channels represents the number of discrete sections that can be used for processing different parts of the incoming sound signal. The more channels in a hearing aid, the greater the flexibility in programming, as the hearing aid prescription can be customized across the different frequencies, or pitches. This customization of the hearing aid is called its frequency response.
Directional microphone systems
Directional microphone systems are designed to give a boost to sounds coming from the front of the wearer and reduce sounds coming from other directions. Different system designs block out more or less of the sounds coming from behind the wearer. These systems improve speech understanding in background noise. Satisfaction is higher for hearing aids with directional microphone systems than for hearing aids without them.
Digital noise reduction
Digital noise reduction systems analyze the signal to determine if it contains unwanted noise. If this unwanted noise is detected, this system reduces the level of noise. This feature makes the background or environmental noise less annoying for the hearing aid wearer and increases their listening comfort. Digital noise reduction has been shown to be effective and preferred by hearing aid wearers.
Impulse noise reduction
Similar in purpose to the digital noise reduction, impulse noise reduction seeks to improve listening comfort. This system detects any transient loud noises, such as car keys rattling, typing on a keyboard or dishes rattling, and smooths them out so they don’t startle or annoy the hearing aid wearer.
Feedback management systems
Feedback management systems are used to combat the inevitable feedback loops that occur when a microphone and speaker are placed in close proximity, as they are in a hearing aid. These feedback loops create an annoying whistling sound that can get in the way of listener comfort. Feedback management algorithms can be implemented in very differently for basic hearing aids or advanced hearing aids. Basic feedback management systems may reduce the overall amplification in order to remove the whistling. Advanced feedback management systems reduce or eliminate whistling without affecting overall amplification of the hearing aid.
Telecoil is a wireless feature that picks up electromagnetic signals from compatible telephones or looped rooms. This technology has been available in hearing aids for a very long time and can often be included in very basic models. Because the signal of interest is directed to the hearing aid’s processor without using the microphone, telecoil can improve the signal to noise ratio while eliminating the potential for feedback. Public performances, tours, exhibits and worship services are commonly made accessible to individuals with hearing loss via telecoil.
Frequency modulation (FM) compatibility is a wireless feature that enables hearing aids to connect with FM systems, sometimes via a special attachment to the hearing aids called a boot. FM systems can be used alone or with hearing aids. Like telecoil, FM systems improve the signal to noise ratio without causing a feedback loop in the hearing aids. FM compatibility is especially important when selecting hearing aids for children because these systems are commonly used in educational settings to ensure that the teacher’s voice is heard above the clamor of the classroom.
Advanced hearing aid technology
As mentioned above, several of the basic hearing aid technologies can be implemented in very sophisticated ways. As the level of technology increases, hearing aids become more automatic and are equipped with more features to help individuals better communicate in difficult listening situations. For example, instead of utilizing two channels to separate sound for processing, a hearing aid with advanced technology may have eight or more channels. This splits the signal into even smaller frequency bands and therefore offers a higher resolution of signal processing.
In addition to the basic hearing aid technology, each major hearing aid manufacturer offers several levels of advanced digital technology. More advanced technologies translate to higher price points for hearing aids as well as greater benefits. The following are examples of features that are more likely to be offered in advanced hearing aids. Note that this is not an exhaustive list, as hearing aid research is a very active field.
Bluetooth compatibility is a wireless feature that enables hearing aids to connect to mobile phones and other devices that use Bluetooth, often through an intermediary device. Like telecoil and FM compatibility that came before it, Bluetooth technology has the ability to improve the signal to noise ratio and eliminate feedback from the microphone because the signal bypasses the microphone and directly enters the hearing aid’s processor. A Bluetooth connection is also less likely to experience interference, which can occur with an FM system.
Wind noise reduction
Although fairly specific in its application, wind noise reduction can make a world of different for those who spend time enjoying outdoor hobbies, like golfers and boaters. Wind noise reduction is an advanced hearing aid technology that detects the impact of the wind blowing across the hearing aid microphones and avoids or reduces the amplification of it.
Data logging is a feature that stores data about the listening environments in which you wear your hearing aids and your preferences for programs, volume levels and other features. The information can be accessed by the hearing healthcare professional when you return for a follow-up appointment. Your practitioner will use this valuable information to further customize your hearing aid fitting.
Some hearing aids have a feature that allows them to “learn” the wearer’s preferences. By logging volume control settings and program preferences for certain sound environments, the hearing aids can begin to make these changes automatically when the environment is detected. The goal is to reduce the amount of manual adjustments the wearer is required to make over time.
Binaural processing is generally used to describe any situation in which a pair of hearing aids communicates wirelessly with each other. This relatively new technology has a lot of potential for improving the wearer’s experience because the hearing aids can access information from both sides of the head. It is most commonly used to keep the hearing aids operating synchronously (such as switching from program 1 to 2 at the same time) or to stream auditory signals from one hearing aid to the other.
What are the real world benefits of these features?
Imagine sitting in a typical busy restaurant, having dinner with friends. Sounds are coming from all directions, such as dishes clanking, people talking and laughing at other tables and waiters rushing about. You’re wearing your new hearing aids and listening to a friend who is sitting across from you at the table. She’s telling a joke. Your hearing aids are simultaneously reducing impulse noises like silverware clanking onto a plate (impulse noise reduction), reducing the whir of the ventilation system above (digital noise reduction), suppressing the voices of the people at the tables behind you (directional microphone system) and storing information about the listening environment to be saved for later fine-tuning (data logging). They’re doing all of this automatically while amplifying and shaping the speech signal from your friend. You are free to relax and enjoy the punch line.
This is just one example of today’s sophisticated hearing aid technology in action. To learn more about hearing aids that might fit your needs, contact a hearing professional in your area.
- Types of hearing aid technology, ASHA, http://www.asha.org/public/hearing/Types-of-Hearing-Aid-Technology
- Digital noise reduction: Yes, there is research proving its effectiveness, Hearing Review, http://hearingreview.com/all-news/16215-digital-noise-reduction-yes-there-is-research-supporting-its-effectiveness
- MarkeTrak VI: 10-year customer satisfaction trends in the US hearing instrument market, Hearing Review, http://hearingreview.com/products/15604-marketrak-vi-10-year-customer-satisfaction-trends-in-the-us-hearing-instrument-market
- It’s sync or stream! The differences between wireless hearing aid features, Hearing Review, http://hearingreview.com/continuing-education/21724-it-s-sync-or-stream-the-differences-between-wireless-hearing-aid-features