Purchasing a pair of hearing aids is only one of many factors that must be considered in order to
hear one’s best in spite of hearing loss. Other factors that need to be addressed after hearing
aid purchase include programming and physically fitting the hearing aid to the ear canal.
In this video, we will focus on hearing aid fitting or how
the hearing aid is coupled to the ear canal.
Although there are many different types of hearing aids, we will focus specifically on
Receiver in Canal style which is by far the most popular and widely used style of hearing aids.
This style hits the sweet spot in terms of comfort, great feature set,
ability to fit a wide range of not only hearing losses but also different ear sizes and shapes.
Its ability to fit different ear sizes and shapes is due to
the swappable rubber domes which is what is inserted into the ear canal.
Custom ear molds can even be used instead of the rubber domes with this hearing aid style.
That said, rubber domes are by far more popular than custom ear molds, not because they're always
better, but because they're much easier to fit in the ear canal quickly. Domes come in a variety
of different sizes and styles whether open fit, vented fit, or closed fit. Rubber domes are also
very easy to replace and exchange. If the dome becomes worn out, you can easily replace it,
or if your hearing loss changes, a different dome style can easily be tried.
Rubber domes also minimize a phenomenon known as the occlusion effect.
This occlusion effect occurs whenever the ear canals are plugged up causing one’s
voice to sound boomy and amplifies self generated sounds like chewing.
Rubber domes are typically most appropriate for individuals who
have a mild to moderate hearing loss with the loss primarily being in the
mid and high frequency ranges but with normal low frequency hearing.
This is because rubber domes, especially the open and vented styles, allow the
mid and high frequencies that are being amplified by the hearing aid to combine
with the natural unamplified low frequency sounds that are entering into your ear canal.
Now, if you do happen to have a low, mid, and high frequency hearing loss,
you can use a closed dome to try trap in the low frequency sounds as well.
As great as rubber domes are for a lot of individuals with hearing loss,
custom ear molds can oftentimes be even more appropriate.
Custom ear molds are made by taking a physical impression of the ear and ear
canal using injectable silicone or gel that solidifies after three to four minutes. Custom
ear molds can also vary in size, shape, and materials to not only help keep it
comfortably in place within the ear canal, but to also optimize sound acoustics. Custom ear
molds typically outperform rubber domes for more complex and more severe cases of hearing loss.
This is analogous to listening to music in a perfectly engineered sound-balanced
theater rather than a random room. Similarly, a custom ear mold allows
for an audiologist to precisely engineer the best way to trap sound amplification
within the ear canal which is uniquely different between different individuals.
Custom venting which is a tunnel opening inside of a custom ear mold is also another
reason why a custom ear mold can outperform a generic rubber dome.
By adjusting the exact vent size present in the mold,
the audiologist can precisely select which sounds are allowed to enter into the ear
canal naturally without amplification while trapping amplified sounds within the ear canal.
This audio engineering is all accomplished while preventing whistling or warbling sound feedback
which occurs if the hearing aid’s microphone picks up the amplified sound in a cyclical manner.
The ability to restrict which sounds enter the ear canal naturally also allows your
hearing aid to do a better job of noise reduction and directionality,
so you can cut out a lot more background noise.
Also, wireless music streaming almost always sounds better with a custom ear mold. Why is
that??? Because custom ear molds allow you to trap in the low frequency bass tones more
effectively making music sound much more rich and full. If you use a rubber dome,
a lot of these bass tones will just leak outside of your ear canals and go unheard.
In the case of a mild high frequency hearing loss, an open dome would be the most appropriate
to use because they would allow the low frequencies to enter the ear canal naturally.
Furthermore, an open dome would allow the hearing aid to amplify the high frequencies
enough to make them audible again, all without the risk of feedback or
whistling from the hearing aid as long as the hearing aids are programmed properly.
In the case of mild mid frequency to moderate high frequency hearing loss,
a vented dome would be most appropriate to use because it would not restrict the good
low frequency hearing, but would allow for better amplification of the mid and high frequencies.
In the case of a moderate flat hearing loss affecting the entire frequency range,
we need to be able to trap enough low, mid, and high frequency amplification inside of
the ear canals so it does not leak out which would substantially limit hearing aid benefit. A custom
ear mold would be the best option as long as the proper vent size is created by your audiologist.
The second best choice would be using a closed rubber dome which may risk the occlusion effect.
However, if only a mild flat hearing loss is present,
vented domes may adequately work for most people.
In the case of a steeply sloping high frequency only hearing loss,
a custom ear mold with a custom vent size is also most appropriate because
it can allow for the low frequencies to enter the ear canal naturally,
but without the vent being so large that it allows the hearing aid to whistle. Such
feedback is a risk with rubber domes because of the need to amplify the high frequencies so much.
In the case of a severe to profound hearing loss,
it is critical to use a custom ear mold either without a vent or just a very small pressure
vent to ensure that enough amplification is retained inside of the ear canal.
Attempting to fit a hearing loss severity such as this with a rubber dome would be an
extremely poor decision and ultimately waste an otherwise perfectly good hearing aid.
In summary, to get the most out of your hearing aid, it is very important to select the best
type of rubber dome or even a custom ear mold for your pattern and severity of hearing loss.
Incorrect selection can make a hearing aid not work nearly as well leading to
frustration and dissatisfaction with your aided hearing ability.