An open-fit hearing aid is a modern style of amplification that prioritizes comfort and a natural sound experience. The device is a small, discreet unit that sits behind the ear. Unlike traditional models that fully block the ear canal, the open-fit design uses a non-occluding tip, allowing natural sounds to enter alongside the amplified sound. This design has increased the popularity of hearing aids due to its reduced feeling of being “plugged up.”
Anatomy of the Open Fit Hearing Aid
The open-fit style uses two main configurations: the Receiver-in-Canal (RIC) or a thin-tube Behind-the-Ear (BTE) model. Both styles consist of a small housing unit behind the ear, containing the microphone, amplifier, and digital signal processor. This main body captures environmental sound and processes it according to the individual’s hearing loss.
From the main unit, a thin, nearly invisible wire or acoustic tube extends over the outer ear and into the ear canal. In the RIC style, the receiver (miniature loudspeaker) is located at the end of this wire, sitting directly in the ear canal. The BTE style funnels the amplified sound through the thin tube to the ear canal.
The final component is the soft, non-customized tip, known as a dome, which sits loosely inside the ear canal. These silicone domes feature small vents or openings, which defines the “open fit.” This open design ensures the ear canal is not completely sealed, allowing for better ventilation and the passage of natural sound.
Functional Benefits: Avoiding the Occlusion Effect
The primary functional advantage of the open-fit design is minimizing the “occlusion effect,” a common complaint with traditional, sealed hearing aids. This effect is the sensation that one’s own voice sounds hollow, boomy, or echoic, similar to speaking while plugging one’s ears. This occurs because a sealed ear canal traps the low-frequency vibrations produced when a person speaks or chews, causing them to resonate unnaturally against the eardrum.
The open dome tip prevents low-frequency sound from being trapped inside the ear canal. Because the dome does not block the canal, natural low-frequency sound waves generated by the wearer’s voice can escape the ear, allowing them to sound normal. This design allows unamplified, low-frequency external sounds to enter the ear naturally, mixing with the high-frequency sounds amplified by the device.
Permitting this natural sound flow creates a more comfortable and authentic listening experience, especially regarding the perception of one’s own voice. The open design reduces the need for the hearing aid to process and amplify low-frequency sounds the wearer can already hear. This results in a clearer focus on the frequencies that need support and minimizes the distortion often associated with closed-style fittings.
Limitations and Suitability
Open-fit hearing aids are best suited for individuals with mild to moderate hearing loss. They are ideal for those with a sloping audiogram where low-frequency hearing is normal but high-frequency hearing is diminished. This profile benefits from the open design, which provides necessary high-frequency amplification without occluding low-frequency sounds. The device can also be fitted quickly without the need for a custom ear mold.
However, the open design introduces functional limitations, making it unsuitable for those with severe or profound hearing loss. The open canal allows amplified sound to leak out, which can be picked up by the microphone and create acoustic feedback (a whistling sound). This lack of seal limits the total volume that can be delivered, especially when high levels of amplification are required.
The small size of the device, while discreet, can present challenges for some users. Individuals with dexterity issues may find the small components, such as the thin wire and batteries, difficult to handle and maintain. Furthermore, the open style inherently reduces the effectiveness of advanced features, like directional microphones and noise reduction algorithms, which rely on a sealed ear canal to isolate speech sounds.