No one doubts that in the last ten years hearing aids have become smaller and ''smarter.'' Many are now capable of processing speech and noise in ways we could hardly have dreamed of in years past. Features like multiple bands, wide dynamic range compression, automatic feedback suppression system and directional microphones are now common.
Still, despite these developments, nothing is more effective in increasing the signal to noise ratio (the loudness of speech relative to the noise) than a close-talking microphone (a microphone placed just a few inches from a talker's mouth). And of all the factors that affect speech perception, none are more important than signal to noise (S/N) ratio.
Obviously, if a speech signal cannot be heard over background noise, it will not be understood. Perhaps less obvious, is that the more a speech signal surpasses the noisy background (up to about 20 or 30 dB for a hard of hearing person) the better someone can understand a spoken message. No hearing aid feature yet developed can strip away only the ''noise'' when speech and noise arrive simultaneously at the microphone.
One major issue is that to the hearing aid (and the hearing aid wearer) the ''noise'' may be people the listener would prefer not to hear, while the ''signal'' may be the person with whom the listener is engaged in conversation. In other words, the signal (i.e., speech) and the noise (i.e., other speech) are often very similar acoustically and the hearing aid has no way to know which to amplify and which to squelch!
We do know that directional microphones can improve the S/N. They accomplish this by maximally amplifying sounds originating in front of the hearing aid wearer and surpassing those arriving from other directions. Directional microphones are available in many modern hearing aids. To take advantage of this technology, people wearing hearing aids with directional microphones have to consciously position themselves favorably with respect to the location of the speech and noise (for example; desired signal in front, noise to the rear).
The problem with directional microphones is that they remain fixed to the head! I'm not being facetious - it is physically impossible for hearing aid users to continually locate themselves in an optimum location to receive a desired signal. People move, and sound environments change. Hearing aid users can hardly place their ear six inches from the mouth of the person speaking in all situations! Rather, FM systems can significantly help hard of hearing people to hear better in difficult situations.
An FM system is basically an FM (frequency modulated) radio. A microphone (worn by the talker) receives the signal and a transmitter ''broadcasts'' the signal to the FM receiver, worn by the recipient. Unlike hearing aids, the microphone of the FM system can be placed close to the sound source (i.e., the person speaking) using tiny microphones, often worn on a lapel or collar.
Initially, FM systems were designed for use by hearing-impaired children in schools. In the early days of FM, the classroom teacher wore large microphone-transmitters around their neck and the original FM receivers, which worn on the children's body, directed sound signals to the children's ears via miniature earphones. Eventually, technology and protocols were devised to allow children to use their own hearing aids with FM receivers, and the microphones used by the teachers became lapel and collar microphones. These new systems had a profound impact on the educational placement and performance of children with hearing loss.
FM systems overcame the deleterious effects of poor classroom acoustics (poor signal to noise ratios, deleterious background noise, significant reverb) found in most classrooms. FM Systems assured a highly positive signal to noise ratio while permitting teachers and students full physical mobility throughout the classroom. It was the availability of FM systems that made mainstream placement of children with hearing loss a feasible educational placement alternative.
Few adults, however, chose to use the original FM systems. They were cosmetically unacceptable to many people with hearing loss and too unwieldy for everyday use.
Adults who did employ them, however, reported these systems provided a significant boost in their ability to receive spoken messages in a number of difficult situations (lectures, tours, noisy restaurants). Despite their proven ability to improve speech perception in difficult situations, very few adults were sufficiently motivated (and secure in themselves) to use them. Indeed, many hearing-impaired adults were not informed of the existence of FM Systems, since most hearing professionals ''assumed'' their clients would not be interested in such a cosmetically unappealing device.
This is where the new generation of personal FM systems comes in. These systems are smaller and significantly more convenient to use than the original systems. Microphone/transmitters are about the size of an eyeglass case, but much narrower and can be hand-held or fixed on a person's clothing or on a table top. In fact, new microphone/transmitters are portable and can be thought of as a ''third ear.''
Signals broadcast by the transmitter are detected by an FM ''receiver'' boot, which is plugged into the bottom of many behind-the-ear (BTE) hearing aids. Many newer generation BTE hearing aids accept FM boots. One company makes BTE hearing aids with internal FM receivers. Clients cannot only be informed of the advantages of personal FM systems, but trials are easy to initiate and the benefits are apparent and abundant.
Let's consider some situations in which having a ''third'' ear can be useful. I shall review situations I have experienced and I will comment on other potential applications, particularly in various employment situations.
- One persistent problem people with hearing loss complain of is difficulty hearing their companion in a noisy restaurant. A personal FM system is made to order for this situation. The dining companion simply places the transmitter close to him/her, either on the table, or around the neck (a neck cord comes with the microphone) or in a pocket. That's all there is to it. My wife often reminds me to bring my FM system when we go to restaurants. It makes life easier for me and for her too. Without an FM System, talking to me in a noisy restaurant is a strain. She finds herself leaning over the table, struggling to make sure I understand. With the FM System, she can sit back and relax and we can converse easily.
- The situation is not quite so easy when another person, or another couple is present. In these situations, the FM microphone has to be placed in the most strategic location, as close to everybody as possible. I usually place the microphone between the other people on the other side of the table. To hear the person next to me, I set the hearing aid to the FM/M position, so both the FM system and the hearing microphone are picking up sounds. This situation is far from perfect, but better than trying to hear two or three people with my regular hearing aids. Dinner with a large group of people, or at a banquet is often presents an impossible situation. In those large group situations, one can communicate effectively only with people immediately to one side or the other. The best bet for managing conversations in large groups is usually to employ directional microphone hearing aids, being sure to locate the major sources of noise to one's rear. In other words, taking advantage of a personal FM system does not mean ignoring the potential benefits of directional microphone hearing aids.
- People with hearing loss watch the lips of the person speaking for good reason: it improves their understanding of speech. Combining hearing with vision allows for maximal communication. Virtually everybody ''lip reads'' or ''speech reads'' as acoustic signals deteriorate. However, when driving a car, it is not a good idea for the driver to watch the passenger's mouth while engaged in conversation! Safety while driving takes precedence! But we can have it both ways! By speaking into an FM microphone, the passenger can talk to a hard of hearing driver without the driver taking his or her attention away from the road. Whenever my wife and I take a drive in our car, I bring my FM system. I bring the FM system whenever we drive with another couple too. If we're in the back seat, I place the microphone between the two front seats when talking to the other couple. If the other couple is in the back seat, my wife places the microphone behind me or she hands the microphone to the people in the back seat. Again, not a perfect solution, but a lot better than depending on hearing aids alone.
- A hand-held FM microphone is the best solution for hard of hearing people in noisy group situations, such as a reception or a cocktail party. At such events, people are often standing, talking, and milling around. All one needs to do is place the microphone as close to the lips of the conversational partner as is feasible. This can be awkward at first for both parties! Many hearing aid users feel this is a too public a display of their handicap (Yes -- hearing loss is a handicap no matter how one slices it or defines it). Some conversational partners may react negatively to having a microphone placed near their mouths (while others preen a bit while looking for the hidden camera!). It does take a modicum of assertiveness for hard of hearing people to use FM microphones in this manner, but in a little while, it becomes the most natural thing in the world. FM systems help illustrate that communication is a two-way street and that hard of hearing people bear the greatest responsibility for managing their handicap.
- Many people enjoy watching TV at home. While at home, one can use any number of ''permanent'' TV listening systems to enhance comprehension (infrared, FM transmitters, floor loop systems, etc.). However, ''permanent'' systems are less practical when traveling. While traveling, the hard of hearing person can place their FM systems' microphone/transmitter next to the TV speaker. The close distance between the TV and the FM microphone ensures a loud and distortion-free signal transmitted to a listener. When I compare the FM transmission to what I would understand while using my hearing aids alone, there is a clear-cut advantage to the FM condition. When traveling with my wife, and while using my FM system, I can watch (and understand) TV without disturbing her while she reads.
- I've used FM systems in many settings. FM has been useful during small meetings, while walking down the street in a noisy city, at lectures, and on various tours. The FM system makes it unnecessary for a hard of hearing person to elbow other people aside while trying to get close to the tour guide in order to hear! All that is necessary is for the tour guide to wear the FM microphone. I know of workers in noisy factories who use an FM system to talk to their supervisor or co-workers, interviewers who place the FM microphone close to an interviewee and hard of hearing teachers who require their students to talk into their ''third'' ear.
As these examples illustrate, the listening advantages for hard of hearing people of a personal FM system are many and manifest. The combination of boosting the S/N to a degree not possible with other listening technology, plus the ability to physically place the microphone close to a sound source, makes these systems extremely beneficial.
So why aren't more hard of hearing people using them? Why do we rarely see people using such a system?
Part of the reason has to be the cost/benefit ratio as perceived by the user. Even when there is proven subjective and objective benefit, adults who have tried personal FM systems have elected not to use them when it entailed purchasing them. At the International FM conference in Chicago (November 11-12th 2003) there were two papers that evaluated the performance of people with personal FM systems. In both studies, the acoustic advantages were apparent to the researchers and the clients. One group, those who were able to obtain the FM systems free of charge from the Veterans Administration, opted to keep the systems. They reported they would be willing to pay between one and two thousand dollars extra for the unit, considering the acoustic benefits it afforded them. Still, they didn't actually have to lay the money out.
In the other study, conducted at two separate sites, the subjects were not veterans. Although there was ample evidence that the FM systems substantially improved speech comprehension in noise, and the subjects had ample opportunity to try the systems at home, only four people elected to purchase the FM system -- even with a significant price reduction. That was a very disappointing report. However, the subjects in that study were also required to purchase the expensive hearing aids in tandem with the FM system. We simply don't know what their purchase decision would have been, had they been offered the FM system by itself
So what's the solution? How can we get more people to take advantage of devices that can offer them significant help?
The listening problems of most hard of hearing people who use hearing aids is not as dire as for those people who obtain cochlear implants; those people have reached a point where their hearing problems have become intolerable. On the contrary, most hearing-impaired people ''get along'' one way or another. Those with milder losses may feel they have little difficulty in most situations and that the cost of an additional device is not worthwhile for them. Those with more severe hearing losses, however, while they may ''get along,'' often manage this through a combination of pure denial, lower expectations, restrictions in their daily social and cultural routines, and an acceptance of greater tensions within themselves, their family and their social circles. Often, too, they are simply resigned to their situation, not really understanding or appreciating that some amelioration of their difficulties lies within their grasp.
The largest pool of potential users for personal FM systems are those adults who already wear hearing aids. These people already know the many times and situations in which hearing aids although necessary, are insufficient. These are the experiences that lend themselves to discussions with one's hearing aid dispenser or audiologist to determine if an FM system will improve communication access. Often, the problems described are such that a recommendation for purchase can immediately be made. When there is doubt, a supervised trial program can be arranged to determine if the perceived benefits are worth the cost.
However, unless hearing aid dispensers and audiologists routinely include the FM system evaluation and need for a possible ''third'' ear in their clinical practice, little will be accomplished! Most people with hearing loss have never heard of personal FM systems and know nothing about them. It is the responsibility of hearing aid dispensers and audiologists to make this information available to all of their clients. Of course, the full range of other assistive listening and warning technologies should be presented too!
It is my personal belief that personal FM systems would be widely accepted and used if their cost were dramatically reduced. Adding the cost of two FM boots and an FM microphone/transmitter to the cost of two modern hearing aids is just too big a chunk for most people to swallow. Unfortunately, reducing the price is rather difficult to do unless economies of scale can be applied. This presents a conundrum: More people would have to purchase FM systems in order for their cost to be reduced, but people are reluctant to purchase them because the cost is too high. Still, I believe more people would purchase FM systems even at the present time if they were significantly smaller, and offered better performance.
Ideally, FM systems should be no bigger than a ball-point pen and should be able to hone in on a talker five or six feet away, with a very narrow ''receiver beam.'' In other words, they should be able to ''focus'' in on a talker's voice five or six feet away while rejecting the voice of the person next to him or her! And if they could made to ''multi-task'', that is serve other functions as well (i.e., serving as a remote control for the wearer's hearing aids) this would help ensure their more widespread adoption.
If any hard of hearing person needs to be convinced of the potential value of personal FM systems all they have to do is attend a convention of the Self-Help for Hard of Hearing People, Inc. (SHHH) convention. Personal FM systems have a ubiquitous presence, used by people who know how valuable they are. Any one of these people would be happy to testify to the value these systems offer them in their daily lives.
Mark Ross received his B.A. and M.A. from Brooklyn college and his Ph.D. from Stanford University. He is a Professor Emeritus in Audiology from the University of Connecticut and is currently associated with the Rehabilitation Engineering Research Center (RERC) located at Gallaudet University.