What are Ear Molds for hearing aids?
When a hearing loss patient selects a hearing aid style—such as BTE (Behind The Ear) hearing aids, RIC, CIC, or OPEN FIT—custom-fit earmolds (Ear Molds) are often needed to ensure the best performance, staying in the ear, keeping out noise and giving comfort, especially in noisy situations. An open tube/tip doesn’t keep the noise out, but an ear mold can.
An ear mold is a piece of plastic, acrylic, silicone rubber or other soft material shaped to fit a patient’s ear canal, and/or the outer ear structure (concha) surrounding the ear canal. Ear mold styles vary according to level of hearing loss, and the style of hearing aid with which they’re paired. In many cases, ear molds sit inside the ear canal, hidden from view. Other times, lab ear molds sit in the concha bowl as well as in the ear canal.
If you require a custom ear mold, your hearing care professional will take an impression of your ear canal and outer ear using a quick-setting plastic or silicone-like substance. The impression is sent to a specialty lab where it’s turned into a replica of your ear shape
A good Custom Ear mold will greatly enhance your listening experience. Custom Ear molds are used with Behind-The-Ear hearing aids and Body worn hearing Aids. They are the solution for many common hearing aid problems.
THERE ARE 2 WAYS TO MAKE A CUSTOM EAR MOLD FOR YOUR HEARING AID.
DIY (Do It Yourself) http://earmolds.info/earmold-kits
or have your hearing aid provider make an impression of your ear and send it to a remote ear mold lab.
In order to have a custom earmold made by your Dealer/ provider, Specialist or Audiologist, we need to have impressions of your ear. Making impressions of your ears takes about 15 – 20 minutes.
A Custom Earmold will: 1) reduce the possibility of feedback since a form-fitting Custom Earmold provides a better airtight seal in the ear vs. a generic ear piece dome/tip, (the ‘mushroom’ insert), 2) keep the hearing aid more secure in the ear since it will take advantage of all the curves and contours of the user’s ear to lock it all in place, and 3) help reduce the occlusion effect. Occlusion is where a person’s ears feel ‘stuffy.’ People describe occlusion as if they are talking in a barrel, an echo effect, or similar to having water in their ears. It’s the same effect you have when you talk if your ears are all plugged up.
The occlusion effect is reduced by having the custom earmold vented (or loose fitting). A ‘breathing hole’ or ‘channel’ is usually drilled through the canal portion. This allows the chamber that’s created between the end tip of the earmold and a person’s eardrum to ‘breathe’. Sometimes too much of the volume of the hearing aid escapes through the vent hole causing the aid to feedback/whistle/ squeal. So you can include a series of small vent plugs (they look like tiny little bushings and have different sized inner diameter holes in them) or simply remove a channel along one side or along the bottom, but at the same time restricts the outward flow of air volume to a reduced point so the aid does not feedback. Sometimes the answer is to plug the hole with lambs wool, to act as a filter.
New Custom factory Lab Ear molds have the plastic tubing already installed in it (for BTE, Behind-The-Ear aids). The plastic tubing is what attaches to the aid by slipping it over the earhook end (‘elbow’) of the BTE instrument. This plastic tubing should be replaced at least once a year. It is specially molded for hearing aid and Custom Ear mold uses. If you try to use straight tubing, it will crimp as it makes a right angle into the Custom Ear mold and can prevent sound from passing through.
The HCPB DIY (Do It Yourself) Ear Mold Soft Silicones are for BTE, OPEN FIT, RIC Hearing Aids and Electronic Ear plugs … http://earmolds.info/?tve=true
|The HCPB Instant-Mold, Soft Silicones allows the consumer to fit and finish professional looking, custom earmolds, directly in the home, in only 10 minutes.
The Antidote for Acoustic Feedback
Instant-FIT custom earmolds are molded to reproduce every contour of the ear to finest detail for “The Only True Custom Fit.” In addition, Instant-Mold’s flexible qualities enable the earmold to move simultaneously with configuration changes in the ear canal caused by jaw movement.
Instant-Mold Silicones give you total control
The Instant-Mold Silicones gives you control over every aspect of the custom earmold. You can decide every detail of your earmold. You determine the canal length of the earmold, whether you want a full shell, half shell, or a canal mold, venting, modifying. http://earmolds.info/?tve=true
When To Use Instant-Mold for Earmolds
Attenuation characteristics of hearing aid earmolds.
The purpose of this study was to determine the attenuation characteristics of several hearing aid earmolds. Six earmolds and an E-A-R earplug modified to act as an earmold were evaluated according to the standard procedure. The six earmolds consisted of two types (shell and skeleton) having different materials (Lucite and vinylflex) and different styles (normal and tragus lock). The traditional earmolds provided approximately 17 dB less attenuation as compared with the HCPB earmolds.
The attenuation provided by the traditional earmolds was not influenced by the type, material, or style. The traditional earmolds had a noise reduction rating of less than 3.3 dB, whereas the noise reduction rating for the HCPB earmolds was greater than 18.2 dB. Traditional earmolds should not be considered as a substitute for a hearing protection device. However, E-A-R earmolds could be used as a substitute for a hearing protection device provided the level of the noise minus the noise reduction rating would be acceptable.
Editor’s note: This article is an edited transcription of the AudiologyOnline recorded course Earmolds and More (#16407).
Although it may seem like a basic concept, even the experienced audiologist may run into difficulties selecting the best type of earmold to fit a hearing loss or individual patient. Each mold is inherent of certain acoustical properties to maximize a hearing aid’s potential to deliver sound to the ear. In this article, we will review several earmold styles, materials, modifications, and techniques. The terminology used is meant to be as generic as possible, understanding that there are variations of terms with respect to manufacturer and region.
Custom Fit Earmold Styles
A custom earmold is one usually made from a personal impression of the ear canal and concha area so it is unique to that individual’s ear. Custom earmolds are likely what most people are familiar with. If you have ever looked in an earmold product manual, you have seen the many pages of custom styles and may have felt overwhelmed at what style you should choose. Let’s define and discuss some of these popular styles, as well as the options available. Each style will be described using the full shell or full concha earmold as a reference, since most professionals are well familiar with it.
Skeleton and Semi-Skeleton
A skeleton earmold is a relative of the full shell, with a small hole cut out in the concha portion to make a ring around the bowl of the ear. The semi skeleton earmold removes part of the outer ring and leaves the final mold with either a lower concha lock or a helix lock, depending on the hearing loss, ear anatomy, and dexterity of the patient.
Semi-skeleton lock mold and helix lock.
A helix lock can be utilized for ear deformities, such as “cauliflower ear,” because these types of ears don’t have much of a concha bowl at all, but do have the helix intact. This semi-skeleton earmold is also referred to as a semi-skeleton lock mold
As its name implies, the half shell is simply half of the full shell, cut horizontally across the concha and filling up the lower aspect of the concha bowl (Figure 3). Some ear labs carry different variations of the half shell, wherein the mold may take up only a quarter of the concha. Either way, this kind of mold can serve a cosmetic purpose without losing some of the benefits of a full shell.
Canal and Canal-Lock
The canal mold simply fills up the ear canal only, but can still be vented and tubed the same way as a full shell. A canal lock is simply a canal version earmold with a concha lock that sits in the posterior part of the concha bowl (Figure 4).
The lock version may be used to add a little more stability and retention, as well as aiding the patient with insertion and removal. Some dispensers and audiologists may also use the term “handle” or “lower concha lock” to also indicate a canal lock .
Acoustic modifiers are added to the earmold style, typically that of a skeleton mold, and can alter the acoustic properties (Figure 6). Examples of acoustic modifiers include shortening the canal and opening the sound bore to emphasize high frequencies, as well as adding parallel or y-vents that occupy some of the same space as the sound bore.
OPEN FIT/ RIC Earpieces
Obviously, we have seen a surge in the open-fit hearing instrument market over the past ten years. We have also seen an opportunity to create custom molds to work with these slim tube or receiver-in-the-ear hearing instruments. A large majority of the requests for open fitting molds is for the minuscule earmolds used to hold a slim tube instrument in place. This small earmold may serve three purposes: retention;to possibly provide a small amount of occlusion to allow for higher gain and less feedback, to help with insertion if the patient has dexterity issues or problems holding the standard dome tips that are small and flexible AND TO REDUCE THE BACKGROUND NOISE THAT CAN’T BE DONE SUCCESSFULLY with a Dome/tip alone.
Probably the most popular custom mold for a slim tube is something that is very cosmetic and small: a micro-mold. A micro-mold is a canal style earmold with a sound bore that will fit the selected slim tube, with a very large vent area, or lose outer dimension, to prevent the occlusion effect. The usual idea behind any open earmold is to allow the patient to use what normal hearing sensitivity they have naturally and only use the earmold as a means for directing mid- and high-frequency amplification down the ear canal.
An open skeleton mold has the bottom of the ear canal portion removed, so only the sound bore resides in the ear canal. There is no aspect of a canal allowing for a vent because it is completely removed in this particular earmold. This type of mold is used for a hearing loss with good low-frequency hearing, or for a CROS or BICROS fitting. The open skeleton would be used on the dead ear for retention.
The skeleton 2 earpiece is essentially the same, but it allows you to use a vent plug system to modify the vent size if necessary.
Slim tube canal-lock earmold.
The slim tube canal-lock mold features a small foot around the concha bowl. Even for the size of this small mold, this offers quite a bit of retention coupled with comfort in the canal.
Half-shell earmold for a slim tube.
Although not as popular, a slim tube half shell can also be made, keeping the vent as large as possible. You will not likely see many full-shell slim-tube earmolds, simply due to the inherent acoustic nature of a full-shell mold, although it can be accommodated as a full shell with a large vent.
Receiver-in-the-Canal (RIC) Earpieces
Similar to a OPEN FIT slim-tube option, there are earmolds that will accept the receiver of a RIC instrument and yet still fit into the ear canal. This can often be a challenge due to the small nature of the ear canal anatomy.
Several receiver-in-the-ear style earpieces, including canal and canal lock.
Again, for cosmetic reasons, the most popular version of this mold is the canal earmold.
RIC earpieces are primarily made of silicon across several manufacturers. Occasionally, depending on the concha anatomy or the patient’s preferences, a skeleton mold will be fitted for a RIC instrument. One problem with using a mold with more bulk is that if the receiver wire comes too far out into the concha, then the wire going from the receiver back up over the ear can be too short and pull the instrument away from the ear. Many of these factors- power receiver limitations, configuration of hearing loss, venting limitations, and size of the ear canal- should be considered before ordering this type.
Keep in mind that the receivers do not bend, so you may end up with a receiver against the canal wall in an ear with a sharp bend as you enter the aperture or steeply sloping canals toward the eardrum. Adding an earmold to the end of a receiver might make this situation worse for comfort. The goal is to have the receiver directed toward the eardrum and not against the canal wall.
Unlocking the Mysteries of Earmold Material
Vinyl, acrylic, and silicone earmold examples.
Many professionals are likely familiar with three standard earmold materials: acrylic or lucite, vinyl, and silicone rubber. Acrylic might be considered the old standby. This hard material has been around for a long time, and while a large majority of patients with more significant degrees of hearing loss were moving to softer materials, more professionals are actually going back to acrylic these days. One main reason for this is the advent of better digital hearing instrument signal processing technology and feedback managers. It does not shrink, break down over time, or harden with time (since it is already hard). Additionally, it is the easiest of the three materials to modify or re-tube and glue. From a patient standpoint, it is easy to insert and remove, and it comes in every earmold style and color available. Acrylic material is very easy to clean with most mild cleaning agents, and is resilient no matter how many times the surface has been cleaned. The main problem is that it frequently causes sore ears.
Acrylic is best suited for patients with a softer ear texture. When considering ease of insertion, if the ear is very soft and the skin has lost some elasticity, acrylic material is the easiest for that person to maneuver. The only exception is the soft, delicate ears of infants and children. It would only be in a rare case that an acrylic or hard mold would ever be recommended for a child. The greatest disadvantage of a hard earmold for a child is the potential for injury. A 12 year old who is very active in sports from baseball to soccer would have a potential risk that a ball or other player would collide with his ear, and that hard earmold would injure the delicate ear structure. Generally, soft molds are more comfortable to children with growing ears, as well. There is no magic age where a child becomes able to wear an acrylic mold; however, infants and children learning to walk and navigate should never be fitted with a hard earmold.
A general disadvantage of acrylic material is mainly that it is not flexible. Although it is generally the easiest material to insert, since the mold will not compress it can be difficult to insert into very narrow canals. A flex-canal material can address that problem to some degree, however. Secondly, acrylic earmolds are more prone to acoustic leakage when the ear canal changes shape because they don’t move with the jaw. If someone with a significant loss has excessive jaw movement or the earmold does not stay tight during chewing, that user may experience feedback issues despite a good feedback manager in the hearing instrument.
Vinyl, also known as polyvinyl chloride (PVC), is a material that falls in between acrylic/lucite, which is the hardest earmold material, and the softest materials at ear labs. Vinyl is a softer material for soft or flaccid ears and works well for older individuals or children. It inserts fairly easily, although some argue not as easily as acrylic, and has the advantage of providing a better acoustic seal for high-gain instruments.
It is easily tubed, but does require a glue to hold it in place. Some may argue that vinyl is not easily modified;however, a medium-coarse grinding stone can be used to trim and smooth edges quite nicely in the convenience of your office. The disadvantages of vinyl are that it does shrink, harden, and discolor over time. Very old vinyl earmolds that have hardened, may in fact, look and sound like an acrylic earmold as you tap it on your desk. Vinyl earmolds tend to turn a yellowish-brown with time due to individual body chemistry. Sunlight also speeds discoloration. Because of these inherent property problems, vinyl earmolds need to be replaced more often than acrylic or silicone. Most earmold labs cannot make vinyl earmolds in all of the bright multi-colors or glitters.
Furthermore, vinyl earmolds are not generally recommended for use with patients who have allergy concerns. Many earmold labs offer a boil and saline option, which means the earmold is literally boiled, making the earmold a little more user friendly with people who may report allergies. Now, for the person seeing an allergist for airborne allergies, food allergies, and the like, they might be able to use a boiled vinyl earmold, but usually they require something more neutral such as silicone rubber or polyethylene.
Polyethylene is a semi-hard waxy material, with an appearance much like candle wax. The color resembles an older milky-colored ear hook on a hearing aid. This is the earmold material of last resort for allergic cases. Generally, we encourage you to try everything else before using polyethylene because it is not cosmetically appealing, and it is difficult to modify. It is a very safe mold for extreme allergies, but there are also no color options, and style options are somewhat limited. Keeping a tube in place has also proven to be very difficult with this material, so you may have frequent tubing problems or remakes back to the lab.
Silicone rubber has many advantages. It is very flexible and comfortable, tight fitting for high-gain instruments, and durable, especially when compared to acrylic. Very little change in shape or size occurs over time and it is an ideal material for allergy cases. The disadvantages of silicone include difficulty of ear insertion, especially when it is new. Because it is quite flexible, it almost has a rubbery feel when pressed to the skin and can grab the skin upon insertion. One way to address this is by applying a water-based lubricant to the canal portion of the earmold before insertion. Silicone is not appropriate for patients who have very soft or flaccid ears because it grabs the loose skin and pushes back, making it difficult to get the earmold in with a good fit.
On the original make of the earmold, the tubing is actually not glued. HCPB, DIY earmolds cast the rubber around a pre-formed tube. Most earmold laboratories use a plastic or metal/brass retention device of some sort on the tube. This type of tubing is referred to as a TRS (tubing retention system) tube or tube lock. There is also friction tubing, in which the tubing is tight in the sound bore where tugging does not release the tubing easily.
TRS tubing with a brass lock.
Silicone rubber molds are available for children, from some labs in bright colors, glitters, swirls, and a natural, flesh-looking mold. There are many children who are using silicone earmolds both for the appearance and the durability, but tube retention can be a problem. For children who remove the earmolds by pulling the tube, we can make that tubing permanent in the earmold. using super. By using this product, the tubing adheres to the silicone, but if the tubing is pulled out, the entire earmold must be replaced. Only a very small amount should be used, as a little goes a long way. This process is usually fine for young children who are growing out of the earmolds and will need frequent remakes. Making the tubing more permanent tends to make Mom and the audiologist happy. You just simply replace the earmold as the child outgrows that earmold.
There are few actual allergic problems with silicone, but what some users perceive as a reaction to the earmold can actually be a tolerance problem instead. Silicone does not contain latex, and the gloves we use in our lab while processing this material do not contain latex;the silicone is medical-grade. But the tight fit these earmolds provide, while well-suited for more severe degrees of hearing loss, may cause some discomfort or rejection from the user. Rejection may also come from irritants from the ear itself that can contaminate the soft earmold if not cleaned properly and then inserted back into the ear canal. These problems do not constitute a large majority of these earmold users, however, and most children do tolerate these earmolds quite well.
What is the best choice of earmold material?
The advantages and disadvantages to each material have been addressed above, but how do you choose one over another for varying types of patients and hearing losses? First and foremost, consider the age of the patient and who will most often be handling the earmold, If you are fitting a pediatric patient, you want to first choose something you know they will wear, as hearing aid retention for this population in general can be daunting. Many children wear the silicone earmolds, even though they have a soft ear texture. Compliance to wear the earmolds and hearing aids can be better if they can have a bright color or glitter that makes the earmold personalized. Glitter can be added to the silicone during cure. The soft texture is also more appropriate when we are considering the risk of injury, as discussed previously.
With much older patients, consider the dexterity when choosing an earmold. There may be 80-year-old patients, but do weigh the advantages and disadvantages if choosing a silicone mold for this patient. Your patient may be able to insert the earmold, but with such a tight fit, will he or she be able to remove it without pulling the tubing out? Can this person tolerate an acrylic mold while chewing? Take note of lifestyle factors that may affect the choice of earmold.
Another factor that may play a role in your decision is cost. Decide ahead of time if you think you might have to modify an earmold for a patient. Think about how often you might have to replace the earmold based on patient history, use, and age. For adults, you may consider that for certain patients, once you get the fit just right, you never want to replace it because you may never get it just right again. What will re-tubing costs be?
Ultimately, the choice of earmold is a decision made between patient and audiologist/ specialist. It is good to be well-versed in all types of materials and options available so you can make an educated decision together, weighing the pros and cons.
HCPB earmolds can be easily modified with a finger nail file, http://earmolds.info/?tve=true … unlike the lab silicone molds.
There will be occasions when you will have to modify the canal or concha portions of an earmold. The equipment that you use varies.
Prior to modern “real-time” digital feedback management protocols, the non-negotiable laws of physics required physical separation of the hearing aid’s microphone and receiver to reduce/avoid acoustic feedback. Previously, if acoustic energy exiting the receiver found its way to the microphone, an acoustic feedback loop occurred, creating the familiar whistling noise which patients and professionals find highly objectionable. Closing off the ear canal to physically block the flow of sound from the receiver to the microphone became an acceptable and standard operating procedure.
When air is trapped in the external auditory canal (EAC), the warm, moist, dark environment quickly becomes a breeding ground for fungal and bacteria-based microbes. Closing off the ear canal also interrupts the normal function and flow of cerumen, potentially initiating cerumen occlusion and impaction. As audiologists know that closing off the ear canal also can create the “occlusion effect,” which is the single most annoying side effect experienced by some hearing aid wearers. Nonetheless, until 2001, closing off the ear canal was often the only option for the majority of hearing aid fittings.
Candidacy for Open Ear Fittings:
Occlusion is most likely to be experienced by those with normal or mild hearing loss in the low frequencies. As hearing loss progresses past approximately 40 dB HL in the low frequencies (250 and 500 Hz), amplified sound from the hearing aid is usually sufficient to overcome the perception of occlusion (Dillon, 2001). Nonetheless, open fittings are not only desirable for those with good hearing in the low frequencies. Rather, open ear hearing aid fittings are beneficial for all people requiring hearing aid amplification. The common problem is with an open fitting the background noise is admitted to the ear unless an earmold is fitted that provides some venting.
Previously, as hearing loss increased, hearing aid gain increased. As gain increased, tighter fitting earmolds and hearing aids were required to avoid acoustic feedback. Sealed ear canals, the occlusion effect and tight
fitting hearing instruments were previously assumed to be a standard part of the hearing aid experience. However, with modern DSP based highly effective feedback cancellation algorithms, the hearing aid experience has changed.
Open Ear Acoustics: Technical Pre-requisites:
Two DSP-based pre-requisites are required to achieve non-occluding open ear hearing aid fittings. These are: An effective feedback cancellation algorithm, and a fast “throughput” time (“throughput time” is the time difference between when a sound enters and exits the hearing aid).
Feedback cancellation via digital architecture was eagerly anticipated well before these circuits were commercially viable. In 2001, digital feedback cancellation algorithms and management were able to nearly instantly cancel acoustic feedback without sound quality degradation.
An earmold (ear mold British ear mould or earmould) is a device worn inserted into the ear for sound conduction or ear protection. Earmolds can be produced in different sizes for general use or specially cast from particular ear forms. Some users specify how hard or soft they want their mold to be, and can also suggest this. As a conductor, it improves sound transmission to eardrums. This is an essential feature to diminish feedback paths in hearing aids and assure better intelligibility in noisy-environment communication. The main goal in wearing earmolds is to attain better user comfort and efficiency. Earmold tubes) often turn yellow and stiff with age, and thus need replacement on a regular basis.