How Do Hearing Aids Work?
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A hearing aid picks up sounds with a microphone, processes them according to preprogrammed settings and sends them to a speaker located in or near the ear canal. The audio processing can range from simple amplification to AI-assisted automation. A hearing health specialist customizes the signal processing by programming the hearing aids to amplify specific frequencies that match the signature hearing-loss pattern of the wearer, predetermined by a hearing test. A customized hearing aid has a specific frequency response.
Hearing-loss sufferers usually want to know how hearing aids work so they can understand what features are important, why some types cost more than others and why obtaining them requires a consultation with a specialist. With hearing aids, the more features the device has, the higher the price. The additional features help to improve their performance. Without customization, hearing aids wouldn’t be as effective because they would amplify all sounds rather than particular frequencies.
Digital Versus Analog Hearing Aids
The earliest hearing aids were all analog up until the invention of digital signal processing (DPS). Analog hearing aids directly amplify whatever sound wave the microphone detects. Digital hearing aids, on the other hand, function like minicomputers and convert audio signals to numerical codes, which they then can manipulate to make desirable sounds, such as conversations, easier to hear in noisy environments. Virtually all hearing aids on the market today are digital. Although specialists can adjust the frequencies of analog hearing aids, they are not nearly as customizable due to the specialized features available exclusively in digital hearing aids.
Performance Enhancing Features
Digital hearing aids come with many optional features that work together to help block unwanted noise, boost conversations and provide lifestyle conveniences. Here are some of those features and how they help improve how hearing aids function:
Directional microphones: Because they are facing the same direction as the person, hearing aids with directional microphones can diminish sounds that are behind them and augment sounds that are in front.
Automated digital noise reduction: This feature reduces noise to make audio sound clearer.
Impulse noise reduction (compression): Compression makes loud, piercing sounds that may be irritating sound quieter.
Wind noise reduction: Users who love the outdoors can avoid the sound of the wind blowing on the device microphone with wind noise reduction.
Feedback management systems: This feature helps prevent feedback if the microphone picks up sound from the speaker.
FM compatibility: Direct audio input allows wearers to access signals from computers, CD plays, TVs or the radio without using the microphone.
Telecoil: A T-coil, or telephone switch, picks up signals from hearing aid-compatible wired telephones, as well as audio from public broadcasts, such as those in churches, theaters and auditoriums.
Artificial Intelligence: With this feature, the device can learn the wearer’s preferences and automatically adjust settings, depending on the environment.
Smartphone app: The user can make adjustments, monitor battery life and contact their hearing health provider through an app.
Assisted listening: When calls are directly routed to the hearing aid, some devices can convert the speech into text or even translate speech into other languages.
Data logging: Data logging allows the device to track both user and automated adjustments so a specialist can use the information to fine-tune the settings for optimal performance.
Because each feature adds to the cost, hearing aid wearers need to determine which features are necessary or important to them so they are not paying for the ones they don’t need.
Hearing Aid Components
Most hearing aids are behind the ear (BTE), which means that the main body of the device sits behind the ear and transmits sound through a speaker in or near the ear canal. BTE hearing aids have the following components:
- Body: The body sits behind the ear and stays in place with an ear hook.
- Microphone: This is usually located at the top of the ear hook and picks up sound around the wearer.
- Amplifier: The amplifier, also called a processor, is inside the body and makes the sound louder, as well as performing audio enhancements if those features are included.
- Speaker: The speaker is also called a receiver and sends the audio into the ear canal. The speaker may sit outside or inside the ear canal, depending on the device type.
- Wire or tube: Either a thin, plastic-coated wire or a thin tube, depending on the model, runs from the body to the speaker to transmit signals and power.
- Dome or earmold: A dome fits inside the ear canal, while earmolds fit in both the ear canal and the concha bowl. They both work to prevent sound from escaping the ear canal to avoid feedback.
- Button or switch: A specialist can program the button or switch to control volume or change settings.
- Power source: Many hearing aids have disposable batteries that need replacement, while others have rechargeable batteries, depending on the model.
Other types of hearing aids sit entirely inside the ear canal and have very small bodies that are attached to the speakers. The user inserts them into the ear canal, much like earplugs. Many wearers find these types of hearing aids hard to handle because they are so small. Contact a hearing health provider about hearing aid types and what features might be right for you.