How Hearing Aids Work

To put it simply, hearing aids function just like our ears—with added bonuses.

Senior man wearing a hearing aid

According to the National Institute on Deafness and Other Communication Disorders (NIDCD), “only about one out of five people who would benefit from a hearing aid actually uses one.” Imagine if that many people were driving with uncorrected vision problems!

The reality is that nearly 330 million adults have shown signs of disabling hearing loss around the world. That means 262 million adults go about their daily routine without addressing their hearing loss, putting themselves and their relationships at risk. Left untreated, the hard of hearing may also put themselves in risky situations, e.g., missing the squeal of another car’s tires because the radio volume was turned up so high it drowned out traffic sounds.

Struggling to hear and understand during conversations with others has been linked to a number of cognitive and psychological deficits. Early treatment with hearing aids is the most effective way to keep your mind sharp and possibly prevent existing hearing loss from worsening. As of this writing, FDA-regulated hearing aids are only available with a prescription from a licensed hearing care professional. But before you make the decision to schedule an appointment, you should know how hearing aids work, so that you can make a more informed decision with your doctor.


Components of hearing aids

All hearing aids have the same miniature electronic components, which consist of the following:

  • Microphone(s)
  • Amplifier (most now use digital signal processing)
  • Miniature speaker (receiver)
  • Battery
  • On/off switch
  • Program/function switch (in most digital hearing aids)

Wax guards are installed on most hearing aid models to keep earwax from damaging any circuitry. They also include some form of volume control and programmability, to allow you to adjust the hearing aid to your listening environment. Others include sophisticated filtering (much like an equalizer audio component) that can shape sound to create more natural hearing and help you hear sounds that would otherwise be outside of your audible range.

How much can hearing aids help?

Hearing aids can help individuals with most types of hearing loss, including:

  • Conductive (affecting the middle ear)
  • Sensorineural (affecting the inner ear)
  • Mixed (affecting both)

Those with profound hearing loss or complete deafness may not be helped by hearing aids, in which case a cochlear or other surgical implant may be an option. For those with tinnitus, many models offer therapy features that can provide backing sounds to mask the unwanted noises, or even relegate tinnitus sounds into the background to provide relief without introducing additional sounds. By syncing your hearing aids with other devices, such as captioned telephones and induction loops, you can significantly lower the amount of effort required to hear, improving cognition and overall mental acuity.

Analog versus digital

Some hearing devices you may see advertised are not official hearing aids. They are analog devices, which simply make everything louder. These devices are referred to as Personal Sound Amplification Devices, or PSAPs, and are not regulated by the FDA. More advanced hearing aids, such as the ones you would be prescribed by a hearing care professional, are digital, meaning they filter out noise and improve sound quality while selectively increasing amplification, or gain. By converting sound waves into code before you hear them, digital models are more flexible and can be adjusted for virtually any type of hearing loss and listening environment.

Directional microphones

Modern hearing aids also employ directional microphones, which help you understand the speech you want to hear better by isolating and increasing it over any extraneous sounds. Depending on your surroundings, premium hearing aids will adjust automatically to determine whether to filter sounds based on direction or let them pass through without interference. In general, these microphones favor sounds in front of the wearer but are also programmed to capture and enhance the loudest sound in the environment, no matter its direction. This safety feature allows potential alerts like a person shouting “fire” to be heard even if the sound originates from behind the hearing aid wearer. Because of their high sensitivity, directional microphones sometimes amplify wind noise, so smart hearing aids include programs to reduce that annoyance, as well.

Feedback suppression

Feedback suppression is another highly desirable feature. This reduces that annoying, high-pitched whistle often associated with older hearing aid models. If the microphone picks up a portion of amplified sound from the speaker, it can cause a feedback loop which recycles the same audio into an irritating shriek. This is usually controlled by a tightly-fitted earmold that seals the ear and prevents sound from exiting the canal and into the microphone, but more advanced devices can also recognize feedback digitally and eliminate it before it intensifies.

Waterproof versus water-resistant

As of this writing there aren’t any 100 percent waterproof hearing aids on the market. However, many are water-resistant. The difference is that water-resistance only protects from exposure to normal amounts of moisture, such as sweat or being splashed with some water, not submerged during swimming. If you’re someone whose lifestyle regularly involves spending time on the water, gardening, exercising, or otherwise exposing your hearing aids to the elements regularly, look for a pair rated IP67 or IP68 for resistance to moisture, dirt, and dust.

No matter the water-resistance level of your devices, it is recommended that you keep them moisture-free as much as possible by using a dehumidifier or charger with a dehumidifying function regularly. Along with proper cleaning, this will extend the functional life of your hearing aids significantly.

Rechargeable batteries

Digital hearing aid and its batteries

Hearing aids with rechargeable batteries allow some devices to hold a single charge anywhere from 24 to 48 hours, and only require changing once or twice per year. Many come with a feature that alerts you when the battery is low. Some manufacturers now offer rechargeable hearing aids with lithium-ion batteries that use inductive charging technology. This means you don’t have to align contacts on the hearing aids’ housing with matching contacts in their chargers. The batteries also last on average as long as the hearing aids themselves, so you never have to change them.

Made for iPhone and other compatibility features

Building devices that are Made for iPhone® is a recent trend among hearing aid manufacturers. These products allow you to synchronize with multiple Apple® devices in order to stream telephone calls, music, and video right to your hearing aids. Included with most Made for iPhone hearing aids is an app that allows users to adjust the audio levels and directionality of their device.

The telephone switch, or T-coil, allows you to pick up sound coming from the telephone while reducing feedback when using the phone, and helps you hear better in theaters and other venues where there is either an induction loop or FM system available. This is a great feature for those who hate having to ask for a clunky transmitter at the cinema or theater.

Hearing aid styles

Hearing loss affects everyone differently. That’s why today’s hearing aids are built with customizability in mind to fit with any ear shape and degree of hearing loss. Product models are available in several styles, with many design and color options for your convenience. Each option has its advantages and disadvantages, and should be selected based on the recommendations of your hearing care professional. They will determine your level of hearing loss, evaluate any factors that may affect fit and performance, and then recommend which type of hearing aid will provide you with maximum comfort, convenience, and performance, as well as suit your style preference.

While hearing aids are tremendously helpful when properly fitted and maintained, you should have realistic expectations before purchasing:

  • Hearing aids cannot completely restore normal hearing.
  • It usually takes some time to adjust to wearing and controlling your devices.
  • You may need to try another pair or two before you are satisfied.
  • You will likely need to replace your hearing aids after several years of use, or if your hearing loss becomes more profound.
  • You may find that you are irritated by all the extra sounds you can suddenly hear, such as the sound of your voice or a ticking clock.

Open versus closed hearing aid fittings

A common complaint among hearing aid wearers is known as the occlusion effect, which can best be described as how everything sounds when you have your hands cupped over both ears. Often described as “hollow” or “echoing”, manufacturers have developed methods for overcoming this effect. The portion of a hearing aid that sits inside the opening of your ear canal can either be closed-fit or open-fit depending on your hearing preference. Generally, open-fit hearing aids are notable for their ability to allow lower frequencies to enter the ear undisturbed, addressing the fact that hearing loss almost always occurs in the higher frequencies first.

The sound of a closed-fit dome has been compared to sticking a finger in your ear, leaving your hearing feeling plugged, but enhancing noise reduction. Small perforations cut into open-fit domes allow air and sound to travel more openly throughout the ear, but this can have the negative consequence of reduced directional perception and sound compression. For these reasons, closed-fit domes are often recommended for people with more severe or profound hearing loss.

What are your options?

There are three types of hearing aids, all with different functionality. In general, hearing aids are designed to sit in or behind the ear. You may see different styles referred to by these abbreviations:

  • BTE (behind-the-ear)
  • RIC (receiver-in-canal)
  • ITE (in-the-ear) — These aids are custom-fit to your ears for maximum comfort and can come in one of three types:
    • ITC (in-the-canal)
    • CIC (completely-in-canal)
    • IIC (invisible-in-canal)

Behind-the-ear (BTE)

Behind-the-ear (BTE) hearing aids (for moderate to severe hearing loss) are most often worn by children for safety reasons and ease of use. The circuitry for these devices, which are sturdier and easier to maintain than most, is housed in a plastic case behind the ear. Many include directional microphone systems for improved understanding of speech in noisy situations.

To connect BTE hearing aids to the ear, an earmold is individually shaped for each wearer. This earmold serves multiple acoustic functions, including conducting amplified sound into your ear while improving the positioning and hold of the hearing aid behind the ear. The earmold also seals the auditory canal, acting as a block to prevent acoustic feedback, which is responsible for that annoying, high-pitched whistling often associated with hearing aids. It is also relatively easy to clean.

Open fittings that use a thin tube to connect the BTE hearing aid to your ear are available as an alternative for earmolds. These materials are more comfortable and can help prevent moisture from collecting in your ear. While they are only suitable for certain types of hearing losses, their advantages include a balance of sound quality and comfort.

Receiver-in-canal (RIC)

Receiver-in-canal (RIC) hearing aids (for mild to moderate hearing loss) resemble BTE aids but are usually smaller and less visible. With these devices, the receiver rests inside your ear canal and contains the speaker, while a nearly-invisible microphone tube connects it to the processor sitting behind your ear. One notable advantage of these hearing aids is their ability to reduce feedback at levels higher than other models.

A common criticism of both regular BTE and RIC aids is that their size and positioning makes phone use or wearing glasses uncomfortable. However, because of their convenience—once they’re purchased and programmed, you can leave the hearing care professional’s office wearing them— these are often the first hearing aids people buy.

In-the-ear (ITE)

In-the-ear (ITE) hearing aids (for mild to severe hearing loss) are made to fit in the bowl of your outer ear, either completely (full-shell) or partially (half-shell) filling the space. They are somewhat larger than devices that work inside the ear canal. The major selling point for ITE aids is their customizability, which makes them able to treat a wide range of hearing losses. A hearing care professional takes an impression of your ear and sends it into a manufacturer to be created. Although there is a wait involved, you wind up with a custom-fit hearing aid, making them very comfortable to wear, even with glasses or while using the telephone.

ITE hearing aids can be more visible than custom models that fit inside the ear canal or BTEs/RICs. Because of the proximity of the microphone and receiver, the potential for feedback is higher for ITE aids than for others. Telecoil functionality may also be a bit weaker than what you would find on a BTE model. They are also among the more expensive hearing aids on the market.

In-the-canal (ITC)

In-the-canal (ITC) hearing aids (for mild to moderate hearing loss) are custom-fit to fill inside your ear canal and are only visible from the side. Slightly larger than CIC or IIC models, these hearing aids can include volume control and dual microphones for better directionality. Because of the closeness between the receiver and microphone, feedback is more common with these devices. Also, you’re more likely to have issues regarding earwax buildup and moisture damage than with an ITE.

Completely-in-canal (CIC)

Completely-in-canal (CIC) hearing aids (for mild to moderate hearing loss) are meant to sit entirely in your ear canal, reducing their visibility to almost zero. The position and size of CIC hearing aids makes them great at preventing wind noise, and they can be removed by pulling on a thin plastic cord. They do not come equipped with a telecoil that allows users to tune their device to a magnetic channel or induction loop, because the materials needed to include one would not fit inside the tiny hearing aid casing along with the essential components. For the same reason, only a single microphone fits inside these hearing aids. Vulnerability to damage from moisture and earwax is also a common concern, and you may need to change the tinier battery more frequently.

A few manufacturers have launched “ready-to-wear” CICs that offer the best of both worlds—the instant fit of a BTE or RIC with the discretion and comfort of an in-the-canal device.

Invisible-in-canal (IIC)

Invisible-in-canal (IIC) hearing aids (for mild to moderate hearing loss) are as discreet as their name implies. These devices sit deep in the ear canal and produce very little feedback. Like CIC hearing aids, the IIC models also do not come equipped with telecoil functionality. Battery life is notoriously limited, with even the most expensive devices needing a change after 3-5 days, but the invisibility of these devices is attractive to wearers who would prefer no one notice they’re wearing hearing aids. Relative discomfort and difficult handling are two of the drawbacks wearers express.

Ask a hearing care professional

The best way to correct your hearing loss while suiting your personal style and comfort is with the help of a hearing care professional. With a little patience and the right preparation, the two of you will find hearing aids that can significantly improve your quality of life. Contact your hearing care professional to see if you could benefit from a behind-the-ear or custom-built device today.

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