The Power to Hear is Powered by Batteries

The story of better hearing started a long time ago. As soon as people aged, there was hearing loss. As soon as there were diseases to challenge the ears, and auditory function, there was hearing loss. The first power to help hearing was provided by an involuntary hand, cupped and raised to the side of the head. We've come a long way since those humble beginnings.

We're in the age of silicon, and electrons, plastics, and precious metals. Now the power to hear is provided by an astonishing, sophisticated, and carefully designed energy source, the zinc-air battery.

What makes all of this possible? A small, portable source of electricity, the hearing aid battery, often called a zinc air cell. Almost every zinc air button cell battery is used in someone's hearing instrument. It is the needs of the hearing impaired that guide the design and testing of zinc air cells. The zinc air cell is a tiny device that converts chemical energy into electrical energy. The voltage of the cell is characteristic of the anode material, zinc metal, and the cathode material, oxygen. The source of the oxygen is air. An electrolyte, which is conductive, and full of useful hydroxyl ions (-OH), permits the electrons to flow in an outside circuit as long as there is zinc metal left inside the cell. When all of the zinc has been discharged, zinc oxide is left, and the cell is done.

The zinc air battery is different from any other battery system because it contains only one of the electrode materials, the zinc. The other electrode carries only a small amount of oxygen, and when that is used, it looks for more from the outside air. That's why there are air holes on the bottom of the cell. They allow air to enter the cell as it is being used. The tab that is placed over the vent holes blocks air from entering and moisture from either entering or leaving, during the time that the battery is in storage before the user needs it.

The zinc air battery could even be thought of as being half a battery and a half fuel cell. In a traditional battery all of the materials needed to make electricity are contained inside, placed there during manufacturing. In the case of a fuel cell, the reacting materials are brought together in the fuel cell only when the electricity is needed. In the zinc air cell the zinc and the electrolyte are added during manufacturing, but only the sophisticated air electrode is present. The air comes later, entering the cell as it is needed. There's no air tank strapped on the side, it doesn't take up any extra room. That puts a lot of energy into a small, powerful package. You get electrons on demand and power to hear.

Making a zinc air cell involves many different metals, plastics, and other materials. Each one must be carefully assembled because the materials in a battery want to react with each other. They would, except that we keep them separated, so the only time they react is when an external circuit, such as a hearing aid, calls for the electrons to actually flow.

What materials find their way into a zinc air cell? Besides the zinc, there are parts made of nickel, iron, copper, chromium, manganese, carbon, nylon, PTFE, polypropylene, polyester, polyvinyl, potassium hydroxide, high purity water. In order to put the most electrical energy into the small space that is available, parts are kept thin, and many parts perform several functions at once.

How has the demand on batteries changed?

The new technologies that move the hearing industry are primarily the result of the digital revolution in electronics. Starting with computers, digital signal processing has now become a recognized means of analyzing an incoming sound, and almost instantly sending a customized signal to be amplified, to the output stage of the hearing instrument. This increases the power requirements of the whole instrument, and for the battery there is another demand. DSP circuitry will not function correctly if the voltage drops below a critical level, usually 1.05 to 1.1V.

The hearing aid wearer, your client, probably wants a discrete, unobtrusive, and maybe even an invisible fitting. The smaller, the better, right? That puts an extra demand on the battery, because this high performance instrument now needs to work using the smallest battery possible. Added features, added load on the battery. The end effect is that the user may be disappointed with short battery life. In fact this is the most common complaint that battery companies receive from hearing aid battery customers. The hearing healthcare professional may need to adjust the users expectations, especially if the new aid that they are receiving is one of the new, smaller digital devices, if it serves a more profound hearing loss, and especially if it is going down in battery size. Setting and features increase the power requirements. The formula is pretty straight forward: BATTERY CAPACITY / DEVICE CURRENT = SERVICE LIFE.

The audiologist can help the hearing aid wearer get used to battery use in several ways. One way is to help the wearer recognize that even moderate changes in life style can affect the rate of battery use in the aid. If they find that they are changing batteries more frequently, it may be that they have taken up some new activity, such as mall walking, where there is significantly more background sound that's being amplified. The battery is powering the aid all the time, even when the wearer is ignoring the sound that is being amplified!

As younger people start to wear hearing aids, they will take them into more athletic, and more environmentally challenging situations. Wearing a hearing aid during a vigorous workout may be fine, but it also exposes the aid, and the battery to that dangerous chemical, sweat! Once it is inside the hearing aid, sweat can cause corrosion, damaging the contacts, and other tiny circuit components. It will also react across the narrow gap between the can and the top of the battery, producing a corrosion product that looks rusty. The cell has not leaked, but it is wet, and looks terrible. The chloride ions from the sweat are very destructive to the metal part in the hearing aid, and the fact that they are in a circuit, with an electrical current flowing accelerates the corrosive effect. Hearing aid users should be counseled to keep the sweat out of their instrument. Remove the battery, and dry it off before re-inserting it into the face-plate, or battery door.

Battery Clubs are a good way to build your business. They help maintain contact with your clients, especially those who are heavy battery users. Coupons and special offers encourage your clients to keep your practice at the top of their minds when they think of their battery needs. It helps the hearing healthcare professional get to know what is the normal pattern of battery use, and sense when the use has changed. That may be the key to starting a conversation about possible changes in the client's hearing needs. Has their hearing loss changed? Has the instrument been damaged? Is the person wearing the aid much less, or much more?

The good news for your clients is the fact that zinc air batteries give them the power to hear. The good news for you, the professional is the fact that zinc air batteries are a great way to maintain a year round dialogue with your clients concerning their hearing health, and they also represent a profitable part of your practice.

For more information on hearing aid batteries, please see;

Battery Life: Technical Issues and Answers, by Denis Carpenter, Zinc Air Technical Manager, Rayovac, Madison, Wisconsin.

Are Your Patients Hearing ''Batteries Not Included?'' Julie Strasser, Brand Manger, Rayovac Corp. & Tom Begley, Director of Sales, North America, Rayovac Corp.

Editor's Note: This article was the winning submission for the Audiology Online (www.audiologyonline.com) contest sponsored by Rayovac Ultra Pro Line, for the best new article written for consumers and patients, titled "Hearing Aids: Reasonable Expectations for the Consumer." We offer Dr. Allen our congratulations for her excellent work, and we invite the readers to download (in it's entirety) and distribute this article to their patients for educational purposes. ---Editor

INTRODUCTION:

Since you are considering the purchase of hearing aids, it's important for you to establish reasonable expectations from these highly sophisticated, miniature devices. Acquiring hearing aids is not merely a simple act of going to a store and purchasing a product.

Rather, it is a complex process - one that evolves over time and begins with the hearing-impaired individual accepting the realization that hearing impairment has detrimental effects on interpersonal relationships and safety. The hearing impaired person's motivation to hear well is the single most important factor in determining the success of the hearing aid fitting. It is important to realize that you will not experience the exact same benefits from your hearing aids as your neighbor does. This individuality is a critical component, and I want to emphasize that your expectations should be based on you, your type and degree of hearing loss, your past experiences, and the improvements you personally receive from amplification.

The title of this article implies there are "reasonable expectations" for the consumer. Therefore, there must also be "unreasonable expectations". For the most part, there is only one totally unreasonable expectation - do not expect normal or perfect hearing.

It is my hope that this point-by-point tutorial will help guide you in establishing realistic and reasonable expectations from hearing aids, from the professionals you interact with, through the process of acquiring hearing aids, using them effectively, maintaining them, and living the fullest life possible.

1. Expect others to notice your hearing loss before you do! A common complaint of hearing-impaired individuals is that other people mumble - and if they would just speak up, it would be easier to hear them! This is placing the "blame" externally, rather than accepting the reality that your ears are not as good as they used to be. Realize that it is your hearing. Take that step to have your hearing tested before you blast your loving spouse out of the den with the blaring sound of the TV set. Seek the advice of your local audiologist or hearing instrument specialist (HIS), who you will find listed in the yellow pages under "audiologists" or "hearing aids". Of course, another option is to go to the Healthy Hearing website (www.healthyhearing.com), and if you enter your city and state, or just your zip code, a list of professionals will be created for you.

2. Expect your audiologist/hearing instrument specialist to be knowledgeable, courteous, and accommodating. Your audiologist/HIS will take a thorough case history. He/She is searching for information about your hearing loss, it's probable cause, and whether your offspring may be affected. It is important to establish the presence of any medical condition associated with your hearing loss as this will trigger a medical referral. Comprehensive hearing and hearing aid evaluations will be conducted. These evaluations will provide information about the degree and nature of your hearing loss, as well as your ability to process and discriminate the fine sounds of speech. Comfortable listening levels will be defined, as well as a determination about how well you tolerate loud, intense speech and other sounds. These findings are very important as they allow the professional to pre-set some of the characteristics of the hearing aid's circuitry. You will have time to talk with the audiologist/HIS about the differing styles of hearing aids (in-the-ear, in-the-canal, completely-in-the-canal, behind-the-ear), the advantages and disadvantages of each style, and maintenance issues and costs involved. Approximately 80% of all hearing aids sold fit in the ear¹. After you and your hearing professional determine the best style of hearing aid for your needs, an ear impression will be obtained. The ear impression is a plastic cast of your ear which reveals the exact shape of your ear, so the laboratory can place circuitry in a hearing aid shell that will fit your ear(s) only.

3. Expect differing opinions. If you choose to seek the advice of two or more audiologists/HISs, you may get differing opinions about the "best aid" for you. Everyone in the hearing aid industry acknowledges the fact that there is not a single "best" hearing aid. Rather, there are many excellent hearing aid brands available, and there are many different types of circuitry that may benefit you. Your audiologist/HIS uses the case history information and the evaluation results to make the best recommendation for you and your lifestyle. Expect a recommendation to purchase two hearing aids if both of your ears are hearing impaired and are "aidable." There are many benefits to binaural (two ear) hearing, including being better able to understand speech in noise, and being better able to localize sound. Your audiologist/HIS will explain the advantages of a binaural fitting versus a monaural fitting in more detail². Nonetheless, it is very important to understand that if you have two ears with hearing loss, and you only wear a hearing aid on one ear, you will still have significant hearing problems, even under the best of circumstances. A reasonably good analogy is to consider wearing a single eye glass (monocle) for a two-eye vision problem, such as being near-sighted or far-sighted - it simply will not work well for very long!

4. Expect your audiologist/HIS to assess your hearing difficulties in several environments and define individual goals for you. Although there are many self-assessment scales available, a popular one is the Abbreviated Profile of Hearing Aid Benefit (APHAB) developed by Cox and Alexander³. It may be administered to you prior to and following the hearing aid fitting to identify the benefits you receive from the hearing aids and to measure the reduction of any disabling effects of your hearing loss. The COSI (pronounced "cozy") is the Client Oriented Scale of Improvement which was developed by Dr. Dillon and colleagues at the National Acoustics Laboratory in Australia ⁴. As you will remember from my earlier comments, I emphasized that benefits from hearing aids are highly individualized. The COSI allows the audiologist/HIS to determine, based on your input, five major goals or changes you want to occur as a result of wearing hearing aids. These goals may include hearing your spouse better in the car, hearing your friends better on the phone, or any others that relate to you and your hearing difficulties. These assessments are not like the hearing evaluation given by the audiologist/HIS. These are tools that allow us to measure your self-perception of how your hearing loss affects your activities of daily living and how amplification can improve your quality of life.

5. Expect to be offered a 30 day trial period. Although not always required by law, many audiologists/HISs offer a trial or rental period of 30 days for you to adapt to amplification. You may be asked to pay a non-returnable fee during this time. Ask about this trial period, and if not offered, seek a second opinion. Use this 30 day period to test the hearing aids in the environments that are typical of your lifestyle - not only at home, but also at your friends' and relatives' homes, your favorite restaurant, shopping center, grocery store, or place of worship.

6. Expect a referral to a physician to rule out any medical condition that may contribute to your hearing loss. All hearing aids are medical devices and, as such, are governed by regulations of the Food and Drug Administration (FDA). The FDA requires that all users of hearing aids be examined by a physician, preferably one who specializes in diseases of the ear. If you are over the age of 18 years, you may be given the opportunity to sign a medical evaluation waiver that will allow the audiologist/HIS to proceed with your hearing aid fitting. It is in your best interest to be evaluated by a physician prior to the hearing aid fitting, but particularly so if you have a history of ear problems or hearing loss of unknown origin.

7. Expect the hearing aids to cost more than you think they should. There are three categories of hearing aid technology - analog, digitally programmable, and digital. Analog technology has been around for many years. Aids utilizing this technology are also called "conventional" hearing aids and they are the least expensive. According to the most recent dispenser survey published in the Hearing Review in June of 2001, the average price of a hearing aid with analog technology will cost approximately $900 to $1500 per aid, depending on the size of the aid - the smaller the aid, the larger the price¹. Digital hearing aids use digital signal processing - the newest form of technology on the market. Digital hearing aids are indeed complete computers, similar to the PC on your desktop, but they are the size of a pencil eraser! These aids cost approximately $2500 per aid, similar to your PC. Digitally programmable hearing aids will probably cost somewhere between the conventional price and the digital price. You may benefit from any of the three types of technology. Speak with your audiologist/HIS about the types of circuitry and which would be best for you. Importantly, in 2002, some basic digital hearing aids are available at a lower price than in previous years. Many of the manufacturers have switched the focus of their product lines to completely digital offerings, as digital products are more efficient and have broader application. Consequently, as the demand and sales have increased, the price has gone down a little. The bottom line is that there are many more digital hearing aids on the market in 2002 than there was in 1999, and the prices vary tremendously, as do the products.

8. Expect an initial orientation session with your audiologist/HIS in which you will learn how to handle and care for your new aids. You should invite your spouse or significant other to attend this first critical session in getting oriented to your new aids. During this session, you will be taught how to operate the hearing aids, how to clean them, and how to change the batteries. You will receive written information about your aids - a booklet called a 'User Instructional Brochure' which is a requirement of the FDA. Please note, batteries are particularly important. Please be sure to store them and use them exactly as your hearing healthcare professional advises. Please be sure to keep all batteries way from pets and children. It may be difficult for you to remember all the things the audiologist/HIS tells you during this first session, so don't leave the office without your instructional brochure! It will be very valuable to you, particularly during the first weeks of owning your new hearing aids.

9. Expect a period of adjustment. Remember the 30-day trial or rental period mentioned earlier (see point 5 above)? Once you get your new hearing aids, expect an adjustment period of several days to many weeks to get used to the daily care and maintenance of the hearing aids.

You'll need time to learn how to; insert and remove the hearing aids from your ears, learn to adjust the volume control (some hearing aids have volume controls, other are automatic), learn how to clean them, learn how to open and close the battery door, learn to change the battery, get accustomed to placing the hearing aids in a dry-aid kit for the times when they are not in your ears. As you can see, there is a lot to learn, and people learn at different speeds. I recommend that you go slowly, learn one thing at a time, practice, and stay in contact with your hearing healthcare professional.

Many times, a spouse (or significant other) is very useful in helping you adjust to the new responsibilities of ownership of hearing aids. The largest adjustment you will go through is, of course, listening with your new hearing aids. You will hear sounds that you have not heard for a long, long time. Some of these will be "good sounds", like the songs of the birds or high-pitched voices of children. Other sounds, the "obnoxious ones", are sounds we need to hear for our safety and/or general knowledge of what is happening around us. These are sounds like the refrigerator or air conditioning units humming and buzzing, the sound of our footsteps, or a "knock" in the sound of the car engine. Research in this area has shown that this adaptation or adjustment period may last a few months. It takes time for the brain to re-learn all these sounds. Be patient!

10. Expect your voice to sound different. For many reasons, your voice will sound strange to you at first - like being in a barrel. This is a normal early perception and it is often called the 'occlusion effect'. If you don't adjust to this after a few days, discuss this with your audiologist/HIS. Many times, this feeling can be alleviated through changing the vent size in your hearing aids or changing the amount of amplification you are getting for low-pitched tones. Your audiologist/HIS deals with this issue regularly, and they will be able to solve this with you, over a short period of time.

11. Expect a good, comfortable fit. Initially, it will take a while to get used to having the hearing aids in your ears. You may experience a little soreness or irritation at first, but after a few days or a week or so, you should be able to wear the aids for several hours per day without any pain or discomfort. I always find it reassuring when patients tell me they often forget that they are wearing their aids. Remember - even though the audiologist/HIS will make your ear impressions so your hearing aids will be custom fit, many things can happen in the manufacturing process and any discomfort should be reported to your audiologist/HIS immediately. If your aids are not comfortable, you will not get the maximum benefit from them, and you should not wear them. Report all discomfort or irritations to your hearing healthcare professional, and do not wear the hearing aids until he/she advises you as to how to best address the problem.

12. Expect multiple follow-up appointments. The greatest advantage of digital hearing aid technology is the flexibility in programming the sound quality, as well as many other electro-acoustic characteristics of your hearing aids. These hearing aids are highly sophisticated instruments with many features. The computer software that is used to program your hearing aids allows the audiologist/HIS to make a multitude of adjustments while the aids are in your ears. You can actually hear many of the changes as the audiologist/HIS is adjusting different features or characteristics. Other features will only be noticeable in other environments. So, be sure to tell your audiologist/HIS as much as you can about your listening experiences in many environments. If you are a new user, you may get an initial setting of about two-thirds of the amplification that will be ideal for you. As you get used to your aids, the audiologist/HIS will increase the amount amplification over several visits. This will help in your adjustment period and lessen the chances of rejection due to over-amplification.

13. Expect your audiologist/HIS to evaluate the benefits provided by your hearing aids. This is normally done in at least two ways. First, electronic measurements of "real ear" performance give the audiologist/HIS an idea of how the aids are functioning when the hearing aids are in your ears. Your audiologist/HIS may make measurements in which a small microphone is placed in your ear to measure what is happening in your ear canal with and without the hearing aids in place. This is an objective measure and a starting point for successive changes in the performance of your aids. Secondly, the APHAB, COSI, or other assessment scales may be repeated so the audiologist/HIS can help you evaluate pre- and post-fitting hearing difficulties. These two evaluation methods are important in establishing the benefits you personally receive from amplification. If there are no significant changes in these measures, your audiologist/HIS will need to make additional changes in your hearing aid fitting.

14. Expect to be able to hear well, but not perfectly, in quiet one-to-one situations and most small group settings. In order for you to hear well, we must make sound audible, then comfortably loud. Your hearing aids will amplify sound so speech will become comfortably loud. You should be able to hear most of what is said without having to watch a person's lips all the time. However, even people with normal hearing watch the person speaking in order to gain more information! Even when wearing the hearing aids, you should combine your vision and your hearing to maximize your benefits from the hearing aids. When sound is comfortably loud, it will be easier for you to listen and the stress of straining to hear rapidly diminishes. Therefore, listening in social situations becomes pleasurable again. If everyday sounds are uncomfortably loud, report this to your audiologist/HIS immediately.

15. Expect an optimal "distance for hearing". The best distance for hearing with your aids will be dependent on the type of microphones in your hearing aids, and other factors. The hearing aids may be directional or omni-directional. Find out from your audiologist/HIS which type of microphones you have, and the effective listening range or effective "distance for hearing". People within this distance will be the most audible to you. Once you increase the distance from the source you want to listen to, it will get increasingly difficult to hear - just like without the hearing aids.

16. Expect to have difficulty hearing in noisy situations. You may say that you can hear fine in quiet and that the noisy situations are the ones in which you need the most help. This is a common statement made by individuals who have presbycusis (hearing loss due to aging), noise-induced hearing loss, or any hearing loss where the
high-pitched tones are affected the most. Eventually though, as your hearing loss progresses, your ability to hear in quiet settings is also affected. Background noise is a nuisance for everyone, even normal hearing individuals. As sophisticated as today's technology is, hearing aids still cannot eliminate background noise for you. Some of the more sophisticated digital circuitry can effectively reduce (although not eliminate) background noise. If you are in a lot of noisy environments, it is important to discuss this with your audiologist/HIS when discussing your case history and setting your goals for improvement.

17. Your hearing aids may squeal (also called "whistle," or "feedback") under some circumstances. If a hearing aid is somewhat functioning and has a good battery in it, this squeal (acoustic feedback) will occur when the hearing aid is cupped in the hand. Most users find that this helps determine the status of the battery and it is a good sign! However, you should be able to wear your hearing aids at a comfortable loudness level and not experience this squeal. If you do not have a volume control on your aids, they will squeal when you place them in your ears - until you get them placed comfortably. Sometimes, your aids will squeal if you press the phone too tightly to your ear. Report these events to your audiologist/HIS and determine what is normal, what is abnormal, and what can be done to reduce unnecessary acoustic feedback.

18. Expect repairs. You should realize that hearing aids are incredibly sophisticated devices being inserted in the ear canal where moisture and cerumen (ear wax) is waiting to attack any foreign object! Hearing aids are also prone to being dropped if our fine motor dexterity is a little compromised. Microscopic solder joints that connect the tiny wires of the microphone and receiver to the computer chip in the hearing aid can be jarred loose. All repairs cannot be avoided, but the majority of repairs can be avoided with regular and careful maintenance! Being careful and establishing and maintaining a good preventive maintenance schedule, at home and at your audiologist's/HIS's office, can significantly reduce the number of repairs on hearing aids. Your aids will probably come with a standard one year warranty, and after that, you can purchase hearing aid insurance from a number of companies. Talk to your audiologist/HIS about additional warranty options when you purchase the aids.

19. Expect to buy batteries. Hearing aid batteries will probably last a week or two in the hearing aid. Hearing aid battery service life varies based on the hearing aid circuit and the quality and type of battery and is also dependent on environmental conditions (temperature, humidity etc.). Some people ask why hearing aid batteries don't last as long as watch batteries. The answer is the hearing aid battery accomplishes a great deal more work and requires much more electrical energy than does a watch battery. The information you receive during the hearing aid orientation session will define a reasonable length of time for your batteries. When your hearing aids are new, you might want to keep a calendar indicating the days you change batteries. Report any significant changes in battery usage to your audiologist/HIS. Many professional offices offer battery promotions or special programs for their patients. Ask your hearing healthcare professional about this.

20. There are two 'NEVERs' with batteries. NEVER keep batteries with your medicines, as you might accidentally ingest one. NEVER allow young children to handle batteries, as they might ingest them. All hearing aid batteries are toxic if swallowed. Keep them in a safe place and be sure to recycle your batteries properly.

21. Expect to purchase new hearing aids every 5 years. This may come as a surprise, particularly if you just purchased a set of digital hearing aids! However, hearing aid technology changes rapidly, just like computers, and new technology may benefit you greatly. Some people may keep the same pair of hearing aids for 10 to 12 years, particularly if their hearing loss remains stable over time and if they do a great job with maintenance, but the average life expectancy is about five years.

22. Most importantly, expect to enjoy the sounds of life again! Your hearing aids are a key ingredient to staying active and improving the quality of your life. You will once again enjoy social events, leisure activities, and conversations with your family, friends, and co-workers. Your hearing aids will also help you hear sounds to keep you safe and well.

References

1. Strom, K. E. (2001). The HR 2000 dispenser survey. The Hearing Review, 7 (6), 20-42.

2. Staab, W. J. (2000). Hearing aid selection: An overview. In Sandlin, R. E. (Ed.), Textbook of Hearing Aid Amplification: Technical and Clinical Considerations (pp 63-64). San Diego, CA: Singular Thomson Learning Publishing Group.

3. Cox, R. M. and Alexander, G. C. (1995). The abbreviated profile of hearing aid benefit. Ear & Hearing, 16 (2), 176 - 186.

4. Dillon, H., James, A. and Ginis, J. (1997). Client Oriented Scale of Improvement (COSI) and its relationship to several other measures of benefit and satisfaction provided by hearing aids. Journal of the American Academy of Audiology, 8 (1), 27-43.

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