by Neil Bauman, Ph.D.
No, CROS hearing aids are not angry. CROS is an acronym for “Contralateral Routing Of Sound.” “Contralateral” is just a fancy word that means “on the other side.” Thus, very simply, a CROS hearing aid takes the sound arriving on one side of your head and feeds it into your opposite ear.
CROS Hearing Aids
CROS hearing aids are for people who are deaf in one ear and have normal, or near normal, hearing in the other ear. They consist of two parts. The person wears what looks like two hearing aids in one of two styles—either a behind-the-ear (BTE) aid, or a large (full shell/half shell) in-the-ear (ITE) aid.
The “hearing aid” on the deaf ear basically consists of a microphone (to pick up sounds on the deaf side) and a transmitter. The transmitter sends these sounds (either via a cord joining the two “aids,” or more commonly, via radio waves) to the “hearing aid” on the good ear.
This second part of a CROS aid system basically consists of a (radio) receiver (if using the wireless system) and an amplifier. It amplifies the sounds it receives from the deaf side, and then feeds these sounds into the good ear via a plastic tube (if a BTE style), or directly into the ear canal (if an ITE style). CROS ear molds are of an open fit design so they don’t block the sounds the good ear hears naturally.
Incidentally, you don’t need a tightly-fitting ear mold as feedback isn’t an issue with CROS aids since the microphone is on the opposite side of your head—well away from the “ear mold.” Besides, since the person has normal or near normal hearing, the sound doesn’t have to be amplified much.
Bi-CROS Hearing Aids
Bi-CROS hearing aids are similar in many respects to CROS aids, but have this one major difference. They are for people who are deaf in one ear and are hard of hearing in their other ear.
The part that is worn on the deaf ear is identical to the CROS aid. The difference is on the side of the ear with the hearing loss. This part of the Bi-CROS system does the same thing as the CROS system did, but, in addition, it also includes a “regular” hearing aid for the hard of hearing ear.
The Bi-CROS unit combines the signals from both ears and then feeds them into the hard of hearing ear via a normal tightly-fitting ear mold, as otherwise there could be problems with feedback.
Why would you want CROS or Bi-CROS aids? The truth is, they are an excellent solution to your single-sided hearing problems, especially if you often sit so that people typically talk to you from your deaf side. For example, if you are driving a car and your right ear is deaf, you will have great difficulty (and be totally frustrated) trying to hear your passengers. A CROS aid can really benefit you in this and other such situations. With these specialized hearing aids, available from most major hearing aid manufacturers, because you will be hearing so well, you will be CROS, but not angry.