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​CROS and BiCROS

Hearing Aids


​CROS and BiCROS Hearing Aids

​CROS hearing aids (where CROS stands for "Contralateral Routing of Signal") are generally intended for use by individuals who suffer from unilateral hearing loss. That is, they have some degree of hearing loss in a single ear, causing them difficulties in everyday conversations and potential issues regarding distance perception. BiCROS hearing aids are slightly different, and are intended for use by people who have almost total hearing loss in one ear, and partial hearing loss in the other. So, the two are related, but are suitable for very different patients.

In both BiCROS and CROS hearing aids, the aim of the device is to recreate the sensation of binaural hearing (even auditory perception in both ears). How do they do this? The system that hearing aid engineers have arrived it is fairly simple. In CROS systems, the poorly functioning ear is fitted with a microphone, while the ear with relatively functional hearing is fitted with a receiver unit. When sounds are detected by the microphone at the poorly functioning ear, they are automatically transmitted to the receiver on the other side, allowing the wearer to achieve the sensation of binaural hearing.

In BiCROS systems, the setup is similar. The ear with the lowest quality hearing is fitted with a microphone, which detects noises in the local area, and beams them wirelessly to a hearing aid attached to the other ear. This hearing aid than functions like a normal BTE or ITE device, helping to adjust for the poor auditory abilities of the ear with better hearing quality. Because of this, the hearing aid component of effective BiCROS devices needs to be precisely balanced to account for the difference between the two ears - something that modern hearing aids make relatively easy with smartphone apps and hearing aid processors.

One question that arises for some people suffering from unilateral hearing problems is why systems like this would be preferable to simply using a hearing aid in the ear with poor auditory performance? Well, CROS/BiCROS devices are suitable when one ear has little to no hearing ability, or when the difference between the two ears is so large that it affects the quality of life of the individual concerned.

The benefits can be huge, including restoring the ability to have normal conversations, to listen to music on standard stereo systems, or enjoy the experience of attending movie shows. But these benefits are amplified when CROS/BiCROS devices are fully-equipped with technology which supplements their core elements. For instance, they may come with settings to minimize feedback and whistling, and sophisticated directional microphones which can pinpoint specific sources of noise and focus on them - making life much easier in very noisy environments.

CROS/BiCROS hearing aids depend on having reliable ear-to-ear streaming technology on place. Without this, their efficacy is drastically reduced, although older models do still manage to replicate binaural hearing using wires passed behind the hearer's head. With reliable streaming, these products can make things like telephone conversations or listening to audio players much easier, convenient, and more enjoyable.

This type of hearing aid is really a variant of the other types we have already discussed. In fact, it's possible to purchase CROS/BiCROS devices in both BTE and RIC versions, depending on which one feels most comfortable for the user concerned.

If they have a drawback, it's that CROS/BiCROS devices often require larger units to accommodate extra battery capacity. However, given their specific benefits for patients with unilateral hearing loss, this is often a price worth paying. As with BTE hearing aids, any extra visibility can be compensated for by customizing the look of CROS/BiCROS hearing aids, so that they harmonize with skin or hair tone, and ensuring an attractive cosmetic profile.

CROS hearing aids (where CROS stands for "Contralateral Routing of Signal") are generally intended for use by individuals who suffer from unilateral hearing loss. That is, they have some degree of hearing loss in a single ear, causing them difficulties in everyday conversations and potential issues regarding distance perception. BiCROS hearing aids are slightly different, and are intended for use by people who have almost total hearing loss in one ear, and partial hearing loss in the other. So, the two are related, but are suitable for very different patients.

In both BiCROS and CROS hearing aids, the aim of the device is to recreate the sensation of binaural hearing (even auditory perception in both ears). How do they do this? The system that hearing aid engineers have arrived it is fairly simple. In CROS systems, the poorly functioning ear is fitted with a microphone, while the ear with relatively functional hearing is fitted with a receiver unit. When sounds are detected by the microphone at the poorly functioning ear, they are automatically transmitted to the receiver on the other side, allowing the wearer to achieve the sensation of binaural hearing.

In BiCROS systems, the setup is similar. The ear with the lowest quality hearing is fitted with a microphone, which detects noises in the local area, and beams them wirelessly to a hearing aid attached to the other ear. This hearing aid than functions like a normal BTE or ITE device, helping to adjust for the poor auditory abilities of the ear with better hearing quality. Because of this, the hearing aid component of effective BiCROS devices needs to be precisely balanced to account for the difference between the two ears - something that modern hearing aids make relatively easy with smartphone apps and hearing aid processors.

One question that arises for some people suffering from unilateral hearing problems is why systems like this would be preferable to simply using a hearing aid in the ear with poor auditory performance? Well, CROS/BiCROS devices are suitable when one ear has little to no hearing ability, or when the difference between the two ears is so large that it affects the quality of life of the individual concerned.

The benefits can be huge, including restoring the ability to have normal conversations, to listen to music on standard stereo systems, or enjoy the experience of attending movie shows. But these benefits are amplified when CROS/BiCROS devices are fully-equipped with technology which supplements their core elements. For instance, they may come with settings to minimize feedback and whistling, and sophisticated directional microphones which can pinpoint specific sources of noise and focus on them - making life much easier in very noisy environments.

CROS/BiCROS hearing aids depend on having reliable ear-to-ear streaming technology on place. Without this, their efficacy is drastically reduced, although older models do still manage to replicate binaural hearing using wires passed behind the hearer's head. With reliable streaming, these products can make things like telephone conversations or listening to audio players much easier, convenient, and more enjoyable.

This type of hearing aid is really a variant of the other types we have already discussed. In fact, it's possible to purchase CROS/BiCROS devices in both BTE and RIC versions, depending on which one feels most comfortable for the user concerned.

If they have a drawback, it's that CROS/BiCROS devices often require larger units to accommodate extra battery capacity. However, given their specific benefits for patients with unilateral hearing loss, this is often a price worth paying. As with BTE hearing aids, any extra visibility can be compensated for by customizing the look of CROS/BiCROS hearing aids, so that they harmonize with skin or hair tone, and ensuring an attractive cosmetic profile.
As their name suggests, ITE hearing aids are worn inside the ear. To enable them to fit properly, they usually have to be custom-made for every individual, creating a molded unit that sits inside the ear without friction or the possibility of becoming dislodged.

In terms of appearance, ITE hearing aids are invisible from behind, unlike BTE (Behind-the-ear) models, and they can also be camouflaged by making the cases in colors which resemble the wearer's skin tone. This makes them a slightly less visible hearing aid option, although they will generally be visible from the side, no matter how their appearance is masked.

ITE heading aids come in a range of different styles, which vary by size and technology. Firstly, there are very small ITE devices, which may be referred to as IIC (Invisible-in-the-canal) or CIC (Completely-in-the-canal).  These tend to be more advanced devices, and have been engineered to be as small as possible. They are inserted deep into the wearer's ear canal, in theory collecting more powerful sound waves as they hit the pinna and penetrate the canal. However, because of their small size, these hearing aids tend to be relatively low-powered, and are associated mainly with moderate or low levels of hearing loss.

IIC and CIC hearing aids are also generally more suited to younger users with greater manual dexterity, as they can be harder to access when battery changes or cleaning are required. And manufacturers generally recommend removing these devices on a daily basis, so users need to be able to access them without any problems. Thanks to their comparatively inconspicuous design, they are popular among people who have mild auditory problems and don't want their hearing aid to be visible.

The second type of ITE hearing aids are called ITC (In-the-canal) devices, and are positioned much closer to the opening of the ear canal. In fact, they tend to rest on the inner part of the outer ear bowl, making them more visible, but often more comfortable and esy to access. ITC devices are also usually larger than IIC or CIC versions, which makes them easier to manipulate and maintain, and also gives them longer battery lives, which some users will find appealing.

With a bit of extra size, ITC hearing aids are often able to accommodate additional features compared with those of inner ear varieties, such as better detection of sound based on direction, and dials to control features like volume or noise cancellation. At the same time, the extra power they can mobilize also makes ITC hearing aids a more common suggestion for those with moderate to severe hearing loss.

There are also intermediate hearing aids which bridge the gap between the various ITE designs. They will tend to be smaller than ITE/ITC models, but still have some elements showing from the outside. And they boast greater power levels than IIC/CIC hearing aids, making them more suitable for those with moderate or severe hearing loss.

Whichever model of ITE hearing aid users go for, these devices always include the microphone inside the hearing aid unit, unlike with RIC devices, where the two are separated. Which one is the better option to go for? That depends on the needs of the user and their personal tastes. The great advantage of ITE hearing aids is that they are shaped to suit the dimensions of every individual ear, as well as their hard-to-see fit. So, they will typically be comfortable to wear, and suitable for image-conscious wearers (although more powerful ITE models are far from invisible when in place).

On the negative side, ITE hearing aids often fail to deliver the most powerful performance levels, making them slightly less appropriate for those with a greater degree of hearing loss. Being worn inside the ear, they are also associated with moisture damage and "occlusion", which is the sensation of the wearer's ears feeling "clogged up". These problems can be mitigated by looking after ITE hearing aids diligently, but they are still an issue for some users, and are worth bearing in mind when making a selection.
Hearing aids have delivered huge benefits to individuals afflicted by hearing loss in the past 50 years, and they continue to develop at a rapid rate. For those who are new to the world of hearing aids, it sometimes comes as a surprise to find out how varied their internal and external features can be.

Because choosing the correct hearing aid makes a huge difference to how well it performs, it's essential to learn more about what these devices do (and what they don't). This guide will introduce major varieties such as BTE, RIC, ITE, CROS, and BiCROS devices, and help you find the ideal hearing aid for your specific needs.

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If we break it down, hearing aids are quite simple devices. All they need to do is take noises from the outside world, receive them, amplify them, and then send them to a speaker which conveys them into the ear of the wearer. At this simple level, hearing aids are just a very specific, technologically advanced form of speaker - but there's much more to the technology behind them than that, as we'll see.

For one thing, there is the microphone. This tiny component has to be sensitive enough to pick up music, conversation, and ambient sounds and have the resolution to do so as close to the human ear as it's possible to be. But modern hearing aid microphones need to do more than this. They are also often "directional", which means they can pick up the source of noises, and focus their collection efforts in that direction, improving the quality of the resulting signal. Directional systems usually involve two or more microphones which are both placed inside the hearing aid. By triangulating the distance between them and the strength of external noises, the hearing aid can calculate where sounds are coming from and point the "null" part of the microphone directly towards it. This reduces white noise and interference, blanking out other people's chatter and ambient sounds.

After sounds have been received by the microphone, the hearing aid then turns them into a signal to be amplified, and there are two broad ways of doing so. Firstly, there are analogous hearing aids which convert vibrations from sound into electrical impulses, which in turn pass through an amplifier to make them suitable for transmission. The second type are digital hearing aids, which convert sound into binary data. Both types are still widely available, but digital designs are becoming dominant due to their superior adaptability and ability to work with directional microphone systems.

The third key element of a hearing aid unit is the speaker, which as we'll see can be placed in a variety of different positions. In all cases, they work by delivering amplified sounds to the cochlea, which covered in cilia - a kind of hair which turns sound into nervous impulses, which in turn are interpreted by the brain. In many cases, deafness results from the decay of these cilia, and hearing aids can help compensate for that process.

Aside from those core components of hearing aids, it's also worth noting that advanced versions have many more components. Some have active noise cancellation to reduce unwanted ambient noise. Others feature Bluetooth receivers which can stream audio from mobile phones, mp3 players, computers, or TVs. Many also include "telecoils", which can pick up specific audio feeds such as museum tours or academic lectures. The majority have processing units which store preset programs, and manage all of the various features.

Finally, and very importantly, all have batteries to supply power to their various components. These batteries come in various sizes, and deliver varying amounts of power. That's why you'll find that most hearing aids have various price points, which correspond to weak, medium, and strong models. In advanced hearing aids, batteries can be recharged, but many still require manual changes.

So plenty of innovation and technology goes inside the average hearing aid. The same level of engineering applies to the external aspect of hearing aids as well. For instance, their cases come in a range of different shapes which are adapted to the shape of the human ear. Designers need to balance comfort, ergonomics, the need to fit in internal components, and cosmetic factors – not an easy challenge.

If the hearing aid involves the use of an “earmold” (which contains the speaker), then this has to be precisely molded to suit the shape of the wearer's ear. This is essential for a couple of reasons. Firstly, an ill-fitting earmold is uncomfortable, but it's also dysfunctional. If the seal between the earmold and the ear's concha bowl is imperfect, the hearing aid's acoustic properties will be compromised. But there are some exceptions. In cases where hearing loss is not too severe, earmolds do not need to be airtight, and can be sculpted to look as unobtrusive as possible.

Now we've looked at the interior and exterior aspects of hearing aid design, let's move on to discuss the different hearing aid varieties the market has to offer.

If you have any other questions about the process of buying hearing aids, you can contact me at williamanderson@hearingaidinstitute.com.

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