The most common hearing aids worn today use earbuds, but very few people understand the effect different earbuds have on how much they will like, or not like, the sound quality received from their hearing aids.
Hearing aids that use earbuds are typically classed as Open-Ear or Open-fit hearing aids and are typically referenced as:
RIC (Receiver-In-Canal) or Mini/Micro BTE, Slim-Tube, or OE (Open Ear)
Before we get into the effects that the different earbuds have on the overall comfort of the fitting, the amplification, feedback and occlusion effect - I'd like to briefly discuss why Open-Fit hearing aids were developed and why they are so popular.
The majority of people living with hearing loss have a varied degree of high frequency hearing loss.
The above audiogram illustrates a person who has normal hearing up to and including 1500Hz, and then a sharp decline in hearing in the middle and high frequencies. It's obvious to anybody with a very limited understanding of hearing loss that the goal for aiding this person would be to leave all the information being heard within normal hearing limits alone, while providing the correct amount of amplification to the frequencies with hearing loss, at and above 1500Hz.
Not all that many years ago every hearing aid offered to customers was custom made by taking an impression of the person's ear. Hearing aids were made to fit inside of the ear canal, or an earmold was made, which fit inside of the ear canal and attached to a hearing aid fitting behind the ear.
The problem with custom made hearing aids is in the amount of real estate they take up inside of the ear canal.
If you consider the audiogram above, this person hears the low frequencies normally. If all of the sudden we put a plug inside of the person ear we block the person from hearing the low frequencies naturally.
For years we would do our best to grind big holes through the the shells of hearing aids to allow natural sound to enter the ear canal, this is known as venting.
While venting is helpful, the size of the vent is limited by the size of the ear canal and the size of the components housed inside of the hearing aid.
We could provide large vents for people with really big ear canals, but their is a lot of people with medium and small ear canals that we could only provide small venting too, like the vent in the image above.
With a lack of adequate venting, people often feel plugged up wearing traditional custom hearing aids, and complain of unnatural sound quality, mostly due to the fact that the low frequencies are no longer being heard naturally.
Enter the Open-Fit hearing aid design REVOLUTION!
Open-fit hearing aids take up very little real-estate inside of the ear canal, which allows the low frequencies to be heard naturally, while boosting the middle and high frequencies the appropriate amount.
While Open-Fit hearing aids were developed to fix the problem of occlusion experienced by hearing aid wearers forced to wear custom hearing aids, there popularity has grown, and they are often used for all different types of hearing loss, which is where the importance of understanding the effects of EarBuds comes into play.
Here is a quick breakdown:
Open Hearing Aid EarBuds are meant for people who hear normally or close to normally in the low frequencies. As you can see by the image above, Open EarBuds/Domes have holes perforated through them. This allows the maximum amount of natural air to flow through the ear canal unimpeded; thus allowing a person to continue hearing the low frequency sounds naturally.
The reason each style of earbud comes in different sizes is simply because peoples ears come in all different sizes. Somebody with a really small ear canal will likely find the smallest earbud the most comfortable, while somebody with large ear canals will likely find one of the larger earbuds more comfortable.
EarBuds can also be used for retention, depending on the brand of hearing aid and the anatomy of the person ear.
Most Open-Fit Hearing Aids have a thin plastic arm extending from the ear tube, often referred to as a retention line, which applies a small amount of pressure in the bowl of the ear to prevent the ear tube from slipping out of the ear canal. Some people do not have suitable anatomy for this system to work, so earbuds are selected that fit snuggly against the ear canal walls to create retention.
Closed Hearing Aid EarBuds are meant for people who require a little bit of amplification in the low and middle frequencies. Closed EarBuds allow people who have hearing loss in the low frequencies to also wear Open-Fit hearing aids.
Often people want open-fit hearing aids because they are less noticeable when worn than custom hearing aids often marketed as "invisible hearing aids". Open Fit hearing aids are also a preferred design for people who have very small ear canals. If a custom hearing aid can't be worn, there is still a very good chance that an Open-Fit hearing aid can.
People with the smallest ear canals should choose an Open-Fit hearing aid that places a tube inside of the ear canal, rather than a RIC which places the speaker inside of the ear canal. The reason for this is that the tube takes up less real estate.
Closed EarBuds can also be used to boost the overall amplification of hearing aids. When an ear canal is open, some of the amplified sound bounces off of the eardrum and escapes back out of the ear. By partially plugging or plugging the ear canal, there's a reduction in the loss of amplified sound resulting in greater levels of amplification.
Power EarBuds are meant to provide the maximum ear canal seal. These earbuds are reserved for people looking to achieve the maximum amplification available from their hearing aids.
By creating an air tight seal, the amplified sound can not escape, which will produce the highest gain levels.
Closed and Power EarBuds can also be used if a person's hearing aids whistle or feedback. The feedback is caused from the high frequency sound bouncing out of the ear canal and coming into contact with the hearing aids microphones.
As you have learned, earbuds are about more than just providing a comfortable fit. Earbuds have a significant effect on the sound quality a person will receive and the amount of amplification that is ultimately produced.
The chart below illustrates just how much open and closed earbuds affect the amplification range of a particular hearing aid, in the diagram "occluded earbud" is referring to closed or power earbuds.