When people select BTE (behind-the-ear) hearing aids, they usually don't think about the other marvel of hearing technology, called an ''ear mold.'' The ear mold connects the ear canal to the hearing aid, and literally places the sound in their ears.
Selecting the correct ear mold is very important. It's more important than many people realize because the ear mold and the tubing selected affects the physical comfort and the sound quality of the hearing aid. Ear molds come in a variety of colors from clear, to bright red to neon to camouflage, in a variety of materials from extremely hard, to very soft plastics, and in many designs and styles.
Ear molds should never hurt the ear. Unfortunately, there is a fine line between an ear mold being tight enough to prevent sound from leaking out and causing feedback, and the ear mold being too tight and causing ear pain. Sometimes ''trial and error'' approaches are required to meet the amplification, cosmetic and comfort needs of an individual.
Of course, before the patient receives their ear mold, a cast of their ear is taken. This cast is referred to as an ''ear impression.''
The material selected for taking an ear impression can make a difference, too. Some impression materials (for example; silicone) are extremely firm and durable and they hardly change at all when the ear impression travels (often in the cargo bay) to the ear mold laboratory by air express, UPS or the postal service. These earmolds are able to withstand dramatic temperature and humidity changes, which they may encounter while in transit. Unfortunately, these very stiff impression materials can also temporarily deform or distort the anatomy of a soft or fragile ear canal while the ear impression is being made, and produce an ear mold which is not accurate and does not fit well. Therefore, sometimes less stable impression materials are selected (for example powder based mixes) because they sometimes give better representation of the true anatomy of the ear. Of course, the professional must use their best clinical judgment to determine the best impression material for each specific ear.
Besides comfort, other factors have to be considered before the ear mold is ordered. The texture of the ear is an important consideration. A very soft ear will make insertion of flexible ear molds difficult. Imagine trying to place a mitten on a glove! Therefore, a more rigid material is generally chosen to lessen the effect of the soft ear tissue. On the other hand, an ear which has more cartilage and is ''stiffer'' can use ear molds made of softer materials. In children, soft ear molds are often selected for comfort reasons, and because children are more active, and because the ear mold can give a little with activity, motion and bumps!
The professional has to consider the power and style of hearing aids, and the type and degree of hearing loss. Often times these factors will limit the earmold options available given a particular situation.
Ear molds significantly impact the sound quality of behind-the-ear hearing aids. In fact, there is a whole area of ''ear mold science'' that addresses ''ear mold plumbing'' and the acoustic impact particular widths, depths, inside diameters, outside diameters, vents and other ear mold factors have on sound quality and related issues.
High powered hearing aids have a greater tendency to feedback than do milder gain instrument. Hearing aids designed for a severely sloping high frequency hearing loss also have a greater tendency towards feedback. In general, as hearing loss increases, the amount of power the hearing aid needs to deliver is greater. Therefore, as hearing loss, and hearing aid power increase, keeping the sound from leaking out and causing that annoying squeal called ''feedback'' becomes even more important. So, the ear mold selected has to work with your specific hearing loss and your hearing aids to allow comfort and appropriate sound!
Because the ear is blocked while wearing ear molds and hearing aids, people sometimes complain their voice sounds like they are ''down in a barrel.'' What they are describing is the ''occlusion effect'' which results from having their ears stopped up. It is the same thing which happens when someone sticks their fingers in their ears and speaks. Fortunately, there are many ways to effectively manage this problem through either (or both) ear mold modifications or hearing aid circuit changes.
Venting, is essentially, placing strategic holes in the ear mold, and this allows us change the sound quality dramatically! However, if the vent is too large or in the wrong place, sound can leak through the vent and cause the hearing aid to feedback!
When people complain their own voice sounds too ''loud'' this is sometimes addressed by fitting an ear mold with a larger vent, and less ear mold material. This type of ear mold is called a non-occlusion ear mold and can have different styles; ''skeleton,'' ''semi-skeleton,'' ''non-occluding A mold,'' or, a ''non-occluding B mold.'' Sometimes, ear molds are ordered with special tubing and shape called a ''Libby's horn'' to enhance higher speech frequencies, while reducing the affects of the individuals' voice.
The hearing professional often wants an ear mold with as large a vent as possible, while not allowing the hearing aid to feedback under normal operating conditions. Appropriate venting is often a delicate balancing act to allow as much venting as possible, to minimize the occlusion effect, while at the same time, giving the individual the amplification they need to enhance speech understanding, without excessive feedback.
Fortunately, most digital hearing aids can be programmed to greatly lessen the occlusion effect while providing maximal amplification and minimizing the chance for feedback.
Depending on the type and degree of hearing loss, and the anatomy of the specific ear, the ear mold can be canal size (tiny), half-shell size (medium) or even a ''full shell'' size (large). There are more than 10 different, common ''styles'' of ear molds, depending on the lab which makes them.
Some people's lower jaw joint, the mandibular joint, is so close to their ear canal that every time they open their mouth to talk or chew, the ear mold migrates out of the ear canal, and/or the hearing aid whistles. To address this problem, the dispenser often orders a small handle called a ''canal-lock,'' which is placed on the ear mold for extra retention. It is difficult to predict if a person will need a canal lock on their ear molds. Often, a new ear impression has to be taken in order to add the canal lock to the ear mold. Nonetheless, a canal lock will usually hold the ear mold securely in place preventing movement and feedback when required.
EAR MOLD MATERIALS:
Because the dispenser has many choices of ear mold materials from which to choose, a proper choice of material is important too.
The most commonly used ear mold substance is Lucite, a clear and rigid acrylic material. It is cosmetically appealing and available in all styles and various colors. Sometimes, combinations of materials are used. For example, soft materials may be used in the canal area, while a harder Lucite material is used in the outer ear, to help prevent feedback in severe hearing loss situations, or when a high powered hearing aid is used.
Translucent, flexible plastic ear molds, which conform to the shape of the ear and becomes softer at body temperature may be ordered too. These special ear molds also provide very good seals, and they are sometimes more comfortable too. However, ear molds made from this material usually need to be replaced after several months of use.
Polyethylene is another material used in ear molds and is a smooth, waxy, non-allergenic material. It is fairly rigid, but only available in the color white. This ear mold material is usually selected for individuals who wear high powered hearing aids, but are allergic to plastics. Sometimes, people who have seasonal allergies, or are allergic to penicillin, also have allergies to certain ear mold materials. When people complain to their hearing professional that their ear ''itches'' or ''swells'' or ''turns red'' after they wear the ear molds, professionals will usually choose non-allergenic ear mold materials for them.
Sometimes, very soft, yet durable vinyl material is used, because it gives a good acoustic seal for high powered hearing aids. Often used with children, vinyl ear molds can be made in various strengths and bright colors.
Silicone ear mold material is another option. It shares the softness and durability of vinyl materials but is non- allergenic.
EAR MOLD TUBING:
The tubing which connects the hearing aid to the ear mold can affect the sound quality of the hearing aid and have an effect on the issue of hearing aid feedback. Tubing choices are based on numbers with the most commonly ordered, #13. With high powered hearing aids, this tubing may need to be ''double walled'' or extra thick so the amplified sound from the hearing aid will not pass through the tubing and cause feedback. Some tubing can be coated to lessen the effects of sweating or moisture building up inside the tube which can block the sound from entering the ear.
Today's custom ear molds come in all shapes and sizes for nearly every application, whether used with or without a hearing aid. They can be used anywhere sound levels need to be enhanced, or reduced. Noise protection ear molds can be custom made (starting with an ear impression) to provide outstanding noise protection for a variety of recreational and occupational environments. When fitted properly, some noise protection ear molds, containing an acoustical chamber, will block most noises, while allowing speech to be understood. These are popular with professional football teams, people who enjoy tandem motorcycle riding, professional stock car racers, and professional musicians. For more information on custom made and generic hearing protection devices, click here.
People who do not want water in their ear canals can have floatable swimmer's ear plugs made of a super soft hydrophobic silicone material which can even be made to change color or glow in the dark!
Personal ear molds can be made for mobile telephone earpieces, personal stereo ear inserts, and physician's stethoscopes. Sometimes, newscasters use cosmetically pleasing (almost invisible) ear molds to communicate with their producers during their broadcast. Because professional pilots require listening to specialized equipment, they, too, use custom made ear molds.
The best advice for proper ear mold selection?
Always discuss your specific needs and concerns with your hearing health care professional. Be sure to tell them about any allergies you may have, sound quality issues, and comfort problems. Your hearing health care provider is trained to give you the best product to fit your needs.