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Cros or Bi-cros hearing aid technology can be used when an ear is completely deaf while the other ear has hearing loss but could be improved with a hearing aid.
Some people can hear very little in one ear -- so much so that a standard hearing aid won't help. If a sound occurs on the side of your bad ear, your head literally blocks the sound from reaching your good ear.
Scientifically, this is the "head-shadow effect," and it tends to affect consonants, the higher-frequency sounds important for understanding speech. In short, when you can't hear from one ear, it will be especially hard for you to distinguish "cat" from "hat." This is even harder in environments like restaurants, which have grown noisier over time.
Background noise is a problem for all of us, but worse if you have very little hearing in one ear, a condition called single-sided deafness (SSD) or unilateral hearing loss. Many people simply live with their hearing issue -- just like many people choose to endure untreated hearing loss in both ears. They might ask people to speak to them on their good side. But that isn't a complete solution. They'll still struggle in restaurants or at a noisy event and have trouble locating the source of a sound.
Fortunately, there are solutions, ranging from specialized headphones to hearing aids to surgical implants. When it comes to hearing aids, devices known as CROS and BiCROS are designed especially for single-sided deafness. CROS, the acronym stands for Contralateral Routing of Signals. With a CROS system, you wear hearing aids on both ears, even though you can't hear in one of them. The sound detected by the aid on the “bad ear” is transmitted directly to the aid on the “good ear” side. This gets rid of the"head shadow" effect.
"You are now hearing signals on both sides of your head all in one ear," said Dr. Catherine Palmer, Director of Audiology and Hearing Aids at the University of Pittsburgh Medical Center, Audiology Online.
BiCROS are very similar to CROS hearing aids, except they’re designed for people who have hearing loss in their "good" ear, too.
With a BiCROS system, the aid in your better ear will also be programmed for any amplification you may need. The "Bi" stands for Bilateral. Traditional hearing aids send sound into the ear they are sitting on. With a CROS set up, the device on the non-hearing ear looks like a traditional hearing aid. But "it is really a microphone and transmitter, and is picking up the sound to send it to the device on the hearing ear," Palmer explains. You are a candidate if one of your ears is particularly bad or has no hearing at all.
About 60,000 people in the United States develop this problem every year. The cause might be a viral infection, getting hit on the head, a shortage of blood to the auditory pathway or a benign tumor, called an "acoustic neuroma", on the nerve that connects the ear to the brain.
Another cause is Meniere’s disease, when fluid builds up in part of the inner ear.
For example, teacher Carly Sygrove, shared her story of single-sided deafness most likely associated with Meniere’s disease. While she tried a pair of CROS hearing aids, she said she is still deciding on a treatment option.
"If you notice a loss in one ear or both ears, the first thing you want to do is schedule an appointment with a hearing care professional or ENT (ear, nose and throat doctor), so they can evaluate your hearing and identify the cause of the problem," notes Palmer, a resident of the American Academy of Audiology.
There are drawbacks to wearing CROS hearing aids. They take more time to get used to, and it’s important to know they will not solve all the hearing problems a person may have. For example, they do not improve “localization” of sound -- a person may still not know where a sound is originating from.
This can be especially frustrating in an environment with a lot of background noise, which will be amplified by the devices. While getting used to them can be challenging, the most important thing a person can do is wear them. "Use the device full time -- all waking hours -- in order to get used to this listening arrangement. All clinics have different trial policies. Because CROStechnology poses unique challenges I allow the patient to try them for two weeks before any payment is considered.
If you have this kind of hearing loss or the standard loss in both ears, call a hearing care professional to get a complete hearing test and perhaps study the issue further online.
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Jeff Bayliff is owner of Hear the Birds Hearing Aid Center with offices in Lock Haven and State College.