First, because no sound is produced by the lens itself, there is a low likelihood of acoustic feedback. Feedback is the annoying high-pitched squeal that occurs when amplified sound is picked up by the microphone (of a traditional hearing aid) and re-amplified in a continuous loop. Historically, feedback has been a major issue for hearing aids.
While digital feedback reduction algorithms work well, and eliminate feedback in most hearing aids, there are limits, especially in modern “open” fitting hearing aids (where sound easily leaks out of the ear canal). This is a big advantage of the Earlens system—because there is no acoustic amplification, the potential for feedback is much more limited. This means ample high-pitch amplification can be provided much more readily.
Through direct-drive amplification, the Earlens system also provides more bass than open-fitting hearing aids. When the ear canal is left open, bass tones easily leak out of the ear, leaving the user with a thinner, more high-pitched sound. Losing the bass can have a big impact on the sound quality of music, but can also make speech sound less natural. Earlens overcomes this by driving bass tones directly through the eardrum with mechanical vibrations.
Closed fittings (traditional hearing aids with closed domes or custom molds) can also be a problem. While a more closed fitting does allow for more bass (less bass leakage), many people will not tolerate this as their own voice may sound unnatural, or their ears can feel plugged up. Often, a compromise has to be made by increasing venting, which leaves the ears feeling more open, but again causes a loss of bass tones. Earlens seems to offer the best of both worlds in the sense that it leaves your ear canals open without any loss of bass for amplified sound.
The end result for Earlens is an increased audible bandwidth. That is, a wider range of pitches can be provided since low pitch acoustic sound doesn’t leak out of the ear (with venting) and high pitches can be provided without the fear of feedback.
More bandwidth than traditional hearing aids
Normal human hearing is measured within the pitch range of 20 Hertz (Hz) to 20,000 Hz. According to Earlens, their system provides amplification that listeners in the fitting range can actually use, over a frequency range from approximately 125Hz out to 10,000 Hz. A more traditional hearing aid, if vented enough to be considered “open”, will provide a usable range of approximately 800 Hz to 5000 Hz. If unvented, the range increases to approximately 250 Hz to 7000 Hz, depending on the hearing aid, how it’s programmed, and the physical characteristics of your ear.
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