When ReSound introduced its be by ReSound hearing aid several years ago, it was the first significant innovation in form factors I had seen in a while. By separating the microphone from the unit containing the digital signal processor (DSP) and receiver (speaker), be by ReSound opened up new possibilities for fitting in-the-ear (ITE) and completely in the canal (CIC) custom hearing aids. But be by Resound is an open-fit hearing aid for a limited range of fittings, mainly patients with mild hearing loss at higher frequencies.
Now with its announcement of its Remote Microphone (RM) Technology, ReSound is extending the concept to its popular ReSound Alera hearing aids and other custom hearing instruments. The result is a new class of hearing aids that will provide significant benefits — including more natural acoustic performance, more amplification in a smaller form factor, reduced feedback, and less wind-noise interference — for a broad range of users with mild, moderate and even severe hearing loss.
ReSound Alera hearing aids, introduced last summer, have been extremely popular with ReSound customers attracted by wireless features that enable direct RF streaming of audio from your TV, MP3 player and Bluetooth phone without an intervening streamer unit or induction neck loop. Now, in addition to behind-the-ear and receiver-in-the-ear models, ReSound Alera hearing aids will also feature RM in-the-ear designs, which ReSound says will fit patients with hearing losses ranging from very mild to very severe (100 dB in the high frequencies). “Remote Microphone Technology is a very attractive alternative for hearing aid users with an aversion to Behind-The-Ear (BTE) instruments,” said Dr. Laurel Christensen, Chief Audiology Officer, ReSound. “The placement of the microphone in the concha cymba not only hides it from view, but also improves acoustic performance due to pinna effects.”
ReSound has multiple patents pending on the new design, which features a tiny microphone at the end of a thin tube connected to the processor unit. The tube curls up into the outer ear, with the microphone tucked neatly under the concha cymba. The receiver and processor unit are hidden in the ear canal, while the tube and microphone are nearly completely invisible, hidden under the natural curve of the outer ear (see illustration). Therefore, the Remote Microphone design provides the cosmetic appeal of an “invisible” in-the-ear hearing aid. But at the same time, the placement of the microphone in the outer ear, and its separation from the speaker embedded in the processor unit that sits within the ear canal, provide three distinct acoustic advantages:
- Better amplification: The outer ear is a natural amplifier, compressing audio signals before they reach the eardrum as they travel through the outer ear and into the ear canal. By placing the microphone in the outer ear, the device gets the benefit of the natural amplification and therefore requires less artificial amplification. That means it requires less power to address more severe forms of hearing loss. At the same time, it enables more gain before feedback: the separation of the microphone from the receiver enables more amplification before feedback distorts the signal. In a technical analysis, ReSound researchers found it possible to increase amplification by nine decibels over comparably powered completely-in-the-canal (CIC) hearing aids that integrate the speaker, processor and receiver in the same shell. More natural amplification and gain before feedback translate directly into more help for more severe hearing loss than was possible with previous in-the-ear hearing aids.
- Directivity: According to the ReSound technical analysis, “It is known that the shape and orientation of the pinna provide directivity by enhancing sounds from the front and providing less amplification for sounds originating behind the head. By placing the hearing instrument microphone in the concha, the microphone location effect (MLE) provides enhanced directivity. This placement can improve the perception of signals in the look direction in the presence of noise coming from behind the listener, while using an omnidirectional microphone.” In other words, placing the microphone in the ear takes advantage of the ear’s own ability to place the location of sounds, reducing the reliance on directional microphones that do the job less well than the ear itself.
- Wind noise reduction: any hearing-aid user who has been unable to hear a thing when there’s the slightest breeze outside knows the value of this one. Tucking the microphone under the fold of the outer ear rather than letting it sit exposed to the elements in a BTE or even on the outer face of a traditional in-the-ear design promises to drastically reduce or even eliminate the problem.
ReSound’s new Remote Microphone technology may not be for everyone. Any hearing aid that locates the processor in the ear canal has the potential to create discomfort, blockage of air, occlusion, and feedback. But the cosmetic and acoustic benefits of the new design are intuitive, and it won’t be a surprise if ReSound starts selling a good percentage of its Alera hearing aids in the new form factor.