The Digital Age has brought great advances in hearing-aid technology. Even basic models sold today are greatly improved over old analog models in helping their wearers hear in complex and varying listening environments.

Technological improvements have also let manufacturers pack more processing punch into smaller and smaller hearing-aid models, allowing them to make devices that are more convenient and less obtrusive to wear.

While there are hundreds of hearing aids of various sizes and degrees of sophistication, all consist of three main parts: a microphone that takes in sound; a circuit that processes and amplifies sound; and a speaker that conveys sound to the wearer’s ear. All these components are powered by a small battery.

Hearing-Aid Styles

Hearing aids vary in shape, size, and the way they are worn. They range from tiny devices that nestle completely within the ear canal to larger, more visible models that sit behind the ear. Although any style may include many technologies, the smallest aids tend to have less power to address severe hearing loss. Not all patients are good candidates for each option; carefully discuss your choices with your physician and audiologist.

The figure below illustrates the available styles. The two general categories are behind-the-ear (BTE) and in-the-ear (ITE). Within these two categories are a number of subcategories:

Behind-the-Ear (BTE)

So-named because part of the device—the casing that holds microphone and circuitry components—sits behind the ear, a traditional BTE model consists of the behind-the-ear component and an earmold that occupies the entire ear opening to deliver the sound; the two components are linked by a tube.

“Open-fit,” or “open-ear,” BTE models use a small microphone instead of an earmold, leaving the ear opening largely unobstructed and allowing unaltered sounds to enter the ear. These models are particularly useful choices for users who have good or fairly good hearing in certain pitches, but need help in others. Filling these users’ ears with earmolds would block natural sounds that could be heard without hearing aids—often contributing to a disconcerting inside-a-barrel sensation called “occlusion.” Open-fit BTEs facilitate a more normal mixture of amplified and natural sound, and a more comfortable, less occluded experience for the wearer.

Some open-fit hearing aids simply guide processed sound into the ear canal through a very thin tube that usually ends in a rubber tip. Other open-fit models use a wire instead of a tube, and position the speaker (or receiver) at the end of the wire in the ear canal. These “receiver-in-the-canal” or “receiver-in-the-ear” models are currently a very popular style.

In-the-Ear (ITE)

With ITE models, the entire aid is worn within the ear opening, or entirely within the ear canal, using custom-molded devices. ITE models range in size from “full-shell,” which fill the concha (bowl) of the ear, to “completely-in-the-canal” (CIC) styles, which are almost completely hidden inside the ear canal. “Half-shell” styles are a bit smaller than full-shell styles, and “in-the-canal” (ITC) styles are a bit larger than CICs.

There are also extended-wear devices, which are placed into the ear canal, where it remains until the battery expires two or three months later. It is then replaced with a new device.

Choosing a Style

Since ITE aids are smaller than BTE models, they are popular with patients who want a less visible hearing aid. But newer BTE models are now smaller than in the past, and open-fit technology makes BTE aids more appealing than before. On the other hand, some patients prefer ITE aids because they are compact and keep everything contained within the ear.

If you have severe hearing loss, you’ll probably buy a BTE style, since ITE aids can’t deliver the power you’ll need. Also, BTE aids tend to be more reliable than ITE models, and BTE aids have space for larger easier-to-operate controls.

Features to Consider

Most new hearing aids come with multiple features, some of which have hefty price tags. Features on basic models include:

  • Directional microphones allow a user to control what gets amplified by facing the source of the sound. The microphone takes into account direction and timing cues for sound reaching it, which enhances speech sounds and reduces noise.
  • Automatic volume control provides different levels of “gain” for different inputs. In other words, the hearing aid can sense the level of the sound reaching the microphone and adjust amplification accordingly. Most hearing aids also include an option that lets wearers manually control volume.
  • Feedback cancellation reduces the incidence of whistling or squealing coming from a hearing aid. More expensive models often have more sophisticated controls for this feature.
  • Multiple processing channels allow a hearing aid to divide sound processing into separate frequency regions. This facilitates more flexibility for programming the hearing aid to take into account different degrees of hearing loss at different frequencies. In general, the more channels the more advanced the aid, both in terms of performance and price. But even fairly low-priced hearing aids provide processing in at least a few separate channels, and often more.
  • Telephone coils (T-coils) allow hearing-aid wearers to use a phone without getting feedback. The coils in the hearing aid pick up the signal from the phone in the form of a magnetic field transmitted by the phone. This feature is now used with many other forms of assisted living technologies, such as listening systems for TVs and audio equipment. Many ITE models include T-coils, and (except for the smallest BTE hearing aids, because of size limitations) virtually all BTE models offer the feature.
  • Multiple programs allow the hearing aid to react to sound differently to accommodate different listening environments. Because no single type of signal processing is ideal for every listening situation, multiple programs are like having several hearing aids in one. Examples of different listening environments in which a user might benefit from different programs are noisy restaurants, meetings, and watching TV at home. Switching among programs may be performed manually or automatically in more advanced aids.
  • Because more advanced hearing-aid features usually mean more advanced prices—with the most expensive models at $3,000 or more per hearing aid—think carefully about whether or not the special feature’s added benefit is worth the added cost. Factors to consider include the severity of your hearing loss and your lifestyle. For example, if you lead a relatively quiet life and won’t often benefit from an aid with advanced sound processing, your needs will be different from someone who regularly goes to noisy parties, conferences, or business dinners in restaurants.

Non-basic features usually available for extra cost include:

  • Remote microphones let hearing aids receive a Bluetooth or other signal. This is nice for cell phone use, of course, but some manufacturers also offer systems that allow you to use a remote signal with a TV or landline phone.
  • Remote controls allow wearers to manually adjust volume, program switching, and other settings with a small remote rather than fiddle with controls.
  • Communication between hearing aids enables right- and left-side aids to share information that can optimize hearing response in certain settings, particularly in noisy environments. Some hearing aids use this communication to synchronize manual volume adjustments and program changes; when the wearer changes a setting on one ear it will automatically make the same change to the other.
  • CROS (contralateral routing of signal) adaptation is a system used by persons who have unilateral hearing loss (hearing loss primarily in one ear) whereby a microphone for the ear with poor hearing sends sound it receives to the other ear. Instead of trying to compensate for hearing loss on one side by amplifying sound on that side, sounds that ear should hear are delivered largely unchanged to the ear that can hear them. But this set-up requires wearers to be patient—and highly motivated—to get used to a new way of listening.

One Aid or Two?

If you have hearing loss in both ears, purchase aids for both of them. It will cost twice as much, but the benefits are significant: Two aids will improve your balance and safety by letting you more easily localize and differentiate sounds. They’ll also make it easier for you to understand speech in noisy environments and sort out which sounds are important.