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Winter 2005 Table of Contents
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Hearing Aids

Jim Durkel, CCC SLP/A
Texas School for the Blind and Visually Impaired, Outreach Program

Abstract: This article provides basic information about hearing aids, assistive listening devices and cochlear implants and how they are fitted for children with deafblindness and additional disabilities.

Key Words: Programming, deafblind, hearing aids, assistive listening devices, cochlear implants

A hearing aid is a device that helps a person with a hearing loss get better access to sound. Some of the earliest devices looked liked huge horns or trumpets with the listener holding the small end to his or her ear and pointing the larger end towards the speaker. The good news is that hearing aids have become more sophisticated and useful to more people since that time. The bad news is that hearing aids have become more expensive and rely on fine electronics that often need repair, especially when worn by a young child!

Today's hearing aids use batteries for power, have microphones to take in sounds, have circuits that make the sounds louder and have some way to get the changed sound to the listener's ear.

Size and How the Hearing Aid is Worn

The first way that we categorize hearing aids is by the size and how the hearing aid is worn.

The largest hearing aid is called a body aid. A body aid is about the size of a pack of cigarettes. It is usually held to the listener's chest with a special harness or is carried in a shirt pocket. Body aids used to be necessary for listener's who needed power but as technology has improved they are no longer used very often. Body aids need to be connected to the users ear with ear molds. A wire runs from the hearing aid and connects to the ear mold by way of snap ring.

Behind-the-Ear (BTE) hearing aids are the most common type of hearing aid worn by children. The hearing fits behind the child's ear and is connected to the ear by the use of an ear mold. BTE hearing aids have the advantage of being small but still able to deliver power when needed.

A BTE aid will have a compartment to hold a battery, an on/off switch, and a volume control. Sometimes the on/off switch will have a setting marked T as well. We will talk about the T setting later.

The BTE has a curved hard plastic piece coming out of hearing aid and connecting to the tubing on the ear mold. This part is called the tone hook. Some times changing a tone hook's size and shape can help a BTE aid fit better.

It is easy to lose a BTE aid because they are small. Another problem is that even though BTE aids are small, they can be large compared to a young child's head. Sometimes there just isn't enough ear to hold the BTE against the child's head. Fortunately there are some things that can be done to solve the problem. Adjustments to the tone hook or ear mold often can help hold the hearing aid more tightly to the child's ear. There is also a piece of tubing, called a "Huggy", which connects to the hearing aid and helps hold it against the head.

The other types of hearing aids are In-the-Ear (ITE), In-the-Canal (ITC), and Completely-in-the-Canal (CIC). These smaller aids don't have as much power as BTE aids and are not typically recommended for children. These hearing aids are small and not very noticeable when worn. However, the hearing aid is built into the ear mold. Whenever there is a need for a new ear mold, the hearing aid user is without the hearing aid. Also because of the small size of the hearing aid, very good fine motor control is needed to operate the switches and replace batteries.

Circuits

Until recently, all hearing aids used analog circuits. What is important to know about these hearing aids is that while powerful, this type of hearing was not as adjustable as the newer (and more expensive) digital hearing aids.

Fitting a hearing aid is the process of making sure that the hearing aid is right for the listener's hearing loss. The first part of fitting an aid is to get a good behavioral audiogram. We want to know at what intensity level (decibels or dB) the listener can just detect whether or not a sound is present. This is called the threshold. We need thresholds across the frequency range of speech, from 250 Hertz (low pitch sounds) to 8000 Hertz (high pitch sounds). Hertz is a measure of frequency and is abbreviated as Hz. We look at the threshold the listener has without hearing aids, then look at what we would like the threshold to be. The difference is how much "gain" we need at that frequency. We pick and adjust hearing aids to provide just the right amount of gain for each frequency we test. This is why it is important to have an unaided behavioral audiogram and then redo the testing with the hearing aid; this lets us measure the actual gain the listener is getting.

If the listener can repeat words, it is best to do word discrimination testing with and without the hearing aid. During word discrimination testing, the listener repeats list of words and the percent of words repeated correctly is the word discrimination score. If the word discrimination score doesn't improve significantly, the

hearing aid is not a good fit for the listener. Unfortunately children, especially those who are young or who have multiple impairments, can't do word discrimination testing. Therefore aided and unaided behavioral audiograms are even more important in hearing aid fitting for these children.

While both analog and digital aids may be able to be programmed, analog aids do not allow for as precise setting of gain as digital aids. Digital aids have some additional "bells and whistles" that analog aids can't offer. For example, digital aids do a better job at detecting noise and filtering it out. Digital aids also may have a feature that helps prevent feedback (whistle) that can happen when ear molds don't fit tightly.

Many hearing aids have a feature known as compression. Compression means the hearing aid will amplify quiet sounds more than loud sounds. Without compression, hearing aids will make already loud sounds louder. This can be painful and irritating to a hearing aid user.

Some hearing aids may have multiple programs. That is, the listener can select a setting for listening in quiet and a different setting for listening in noise.

Generally, the hearing aid will be set so that the listener uses it with the volume control set about half way. This gives the least amount of distortion. If a listener is constantly changing the volume control, this may a sign that the hearing aid was not correctly fit to the listener.

Microphones

All hearing aids use microphones to take in sounds from the environment. In typical auditory systems, we take have two ears that take in sound. It is usually best if a hearing user has two microphones at ear level. Having a microphone on each side of the head helps with an important auditory skill, localization. Localization is the ability to know from where in space a sound is coming. This skill is used during orientation and mobility training.

In a body aid, those microphones are on the hearing aid and so are at the level of the listener's chest. This kind of arrangement does not allow for good localization.

BTE hearing aids can have directional or omnidirectional microphones. Omni directional microphones pick up sounds more or less equally in 360 degrees. Directional microphones pick up sounds in coming into the front of the hearing aid more than sounds coming in from other directions. Directional microphones may improve listening in noise but may make localization for travel harder.

Hearing Aids and Assistive Listening Devices

Even with the most sophisticated hearing aids, listening in noise is always hard. Localization may be affected. Following conversations in a large group is a very difficult listening situation. An assistive listening device (ALD) might be needed in conjunction with the hearing aid to help with some of these problems. See <http://www.tsbvi.edu/Outreach/seehear/winter03/ald.htm> for more information about ALDs.

Remember the T setting on the switch controls? T stands for telecoil. This is an alternate way for sound to get into the hearing aid. Inside the hearing aid is a coil that can receive electromagnetic energy. Old telephones used to leak this energy and hearing aid manufacturers took advantage of this fact to help hearing aid users use the telephone more efficiently. These days, you have to special order telephones that leak this energy. Children use the T setting most often to connect the hearing aid to an assistive listening device.

There are other ways to connect a hearing aid to an assistive listening device, such as the use of a "boot." This is a connection on the hearing aid that allows the hearing aid to be directly connected to an ALD. There are some hearing aids that are built to receive information from a remote microphone; the ALD is built in. It is usually preferable to use a personal hearing aid in conjunction with an ALD rather than using the ALD as a personal hearing aid. This is because hearing aids can usually be better individualized than an ALD.

Batteries

Depending on the type of hearing aid and how long each day the listener wears the hearing aid, a typical battery life is 5 to 7 days. Batteries can go any time so it is a good idea to always have spares handy. Hearing aid batteries can look like candy to young children, so care must be taken to dispose of used batteries. Sometimes the most economical thing to do is to join a hearing aid battery club where one can get batteries at a discount as well as getting free packs for every so many packs purchased.

Ear molds

All BTE and body hearing aids need a separate ear mold. The ear mold fits tightly in the ear. Ear molds need to be custom-made for the hearing aid user. They come in a variety of materials and colors. It is not uncommon for children to need a new ear mold every 6 months or so because as the child grows, the ear mold doesn't fit tightly any longer.

If a child is having middle ear infections, there may be feedback with the hearing aid even if the ear mold has a tight fit. If a child has an infection of the ear canal, it can be painful to wear the ear mold. Sometimes hearing aid users have allergic reactions to one ear mold material and have to have the ear mold remade in another material.

Various modifications can be made to the ear mold to make it lighter, more comfortable, and more appropriate for a particular child's hearing loss. Talk with your audiologist or hearing aid dealer if it appears the ear mold is causing discomfort for the child. Sometimes the ear mold just needs a little bit of buffing to remove a small, but irritating, rough spot.

Ear molds need to be cleaned on a regular basis. It is common for earwax to accumulate in and block the ear mold. A mild dish soap and warm water can be used to clean the ear mold. Be sure to let the ear mold dry thoroughly before using it.

Ear molds can be "lubricated" to help get them into a child's ear. Just don't use any petroleum-based product, like Vaseline, to do this as these can cause some ear mold materials to disintegrate.

Learning to use a hearing aid

Hearing aids do not restore hearing or make hearing "normal." They help make some sounds more available to the listener. It is not reasonable to think that it is okay to just put a hearing aid on a child and that will take care of the child's hearing loss.

It may take some time for the child to become used to wearing the hearing aid. Ear molds can be uncomfortable to wear, but over time the hearing aid user learns to ignore them. Hearing aids are giving the child auditory information the child never had before. At first, this information may be overwhelming and frightening to the child. Children may need some specific training to learn to use the new auditory information the hearing aid brings.

Auditory training is an important part of learning to use his or her hearing aid. This includes not only learning to use the auditory information coming in through the hearing aid but also learning how to care for the hearing aid itself.

Buying and maintaining a hearing aid

The life of a hearing aid, even when well maintained, is five to seven years. Hearing aids wear out and when worn by children can be subjected to quite a bit of abuse! It is always a good idea to buy hearing aid insurance when buying a hearing aid. This way costs for repair and/or replacement for lost aids is covered.

Hearing aids can cost anywhere from several hundred dollars to several thousands of dollars. Sometimes private insurance will cover the cost of the hearing aids. For families who meet Medicaid eligibility, Texas has a program known as PACT (Program for Amplification for Children of Texas) administered through the Department of Health. For more information on PACT, see <http://www.tdh.state.tx.us/audio/pact.htm>. For families who don't meet Medicaid eligibility and do not have private insurance may have to explore community resources such as Lions or Soroptomist clubs. For children who are deafblind, the Texas Commission for the Blind may be able to help a family find resources to help cover the cost of hearing aids. Of course, the local teacher for students with hearing impairments may be able to help find local resources, too.

Children with hearing aids should have their hearing with and without the aids tested at least every year. We want to be sure that the child's hearing hasn't changed and that the hearing aid is still a good fit for the child.

A hearing aid can only be of benefit if it is appropriately fitted, worn consistently and constantly, and is working at peak condition. This means that the functioning of the hearing aid should be checked daily. See <http://www.tsbvi.edu/Outreach/seehear/spring00/hearingaids.htm> for more information about checking hearing aids.

Cochlear implants

Sometimes a hearing loss can be so great that conventional hearing aids may not provide enough benefit. If aided thresholds aren't at least 30 decibels or more at least through 2000 Hertz, it might be time to consider the use of a cochlear implant. This is not a decision to be made lightly and requires consideration of several factors beyond just aided and unaided thresholds.

Children with multiple impairments

Children with multiple impairments, including deafblindness do have some different considerations with regards to hearing aids than children with hearing loss alone.

Obtaining good behavioral audiograms (unaided and aided) may require more time and effort. Teaming will be important to help make this happen.

Teaming will also be important when considering the impact of hearing aid use on orientation and mobility training or the use of assistive technology.

Teaming is necessary to discuss the impact of wearing a hearing aid when there are physical disabilities. For example, wearing a BTE hearing aid while in a wheelchair with head support may result in lots of feedback. In this situation a body aid might be a better fit. Some children have no ear in which to put an ear mold and may need use a bone conduction hearing aid.

Finally, teaming is important to insure that all adults in contact with the child who is using a hearing aid understand the importance of consistent use of the aid, understand what auditory skills to expect from the child, and how to deal with any problems related to hearing aid use.

It is important to keep in mind that if a child needs a hearing aid, that child should have an educational label of auditorially impaired (AI) and should have a teacher for students with hearing impairments. This teacher would be able to serve as an information resource as well as serving as a coordinator around audiological testing and hearing aid issues.

Hearing aids, when fitted and used properly, can open up a whole new world to our children with hearing loss!


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