Hearing aid designs

RIC (Receiver in the Channel) or external handset devices

RIC systems are the most widely used devices today. They are worn behind the ear and are small and usually inconspicuous. A thin cable is used to transmit the signal to an external active loudspeaker, which is inserted into the ear canal. These are available in various hearing strengths and, in combination with custom-made earmolds, cover a wide range of hearing losses.

Used for mild to severe sensorineural hearing loss or combined hearing disorders.

Advantages:

• Aesthetically pleasing solution
• Good sound due to the positioning of the transducer in the ear canal
• Offer the current full range of technical achievements
• Bluetooth and battery are standard
• Access to hands-free telephony and audio streaming
• Also available with induction (depending on brand/model)

Disadvantages:

• Can be annoying with glasses, hygiene masks or long hair
• Maintenance-intensive (filter change)
• Can be difficult to operate with impaired vision or haptics

Examples: Phonak Audéo Infinio, Signia Pure Charge and Go, Oticon Intent miniRITE

BTE (Behind the Ear) or Behind the Ear (HDO) devices

Behind-the-ear devices were the measure of all things before the invention of the RIC. As the name suggests, they are also worn behind the ear. In contrast to the RIC system, the loudspeaker is permanently installed in the hearing aid. The sound is directed into the ear canal via an earpiece using a sound tube of various diameters. The latter can be custom-made or, in the case of fixed earpieces, off the shelf.

Used for moderate to severe sensorineural hearing loss, combined hearing loss, conductive hearing loss and residual hearing loss.

Advantages:

• Better usability in the event of haptic or visual limitations
• Treatment of severe to very severe hearing loss more feasible
• Less susceptible to faults
• Bluetooth connection to additional devices possible
• Access to hand-free telephony and audio streaming
• Available with induction coil

Disadvantages:

• More striking from an aesthetic point of view
• Depending on the configuration, the sound may be compromised
• Depending on hearing loss and brand choice without battery, or T-coil

Examples: Phonak Naida, Signia Intuis 4, Oticon Xceed etc.

IDO (In the ear)

In-the-ear devices were a big step towards aesthetics at a time when there was no RIC. In-the-ear devices are fitted into custom-made shells that ideally sit deep in the ear canal. The sound transducer sits in the ear canal in a similar way to the RIC device and is aligned directly with the eardrum. There are different designs (IIC, CIC, ITC). These depend on the space available in the ear canal, the amplification requirement (earpiece strength/size) and the technical design.

Application: For various to moderate to severe hearing losses

Advantages:

• Mostly aesthetic solution
• Natural bundling function of the auricles is retained
• No vendors with glasses, hair or hygiene masks
• Ability to make "normal" phone calls
• Hearing aid can be operated remotely with smart app

Disadvantages:

• If invisible then no battery or Bluetooth
• No audio streaming
• Depending on the ear canal constellation not possible or more visible than RIC
• Not suitable for all hearing losses
• Can cause occlusion (sealing effect) depending on the constellation
• Replacement device not possible for repairs
• high-maintenance
• Not recommended for limited haptics / vision

Examples: Phonak Virto I, Signia Insio IX, Oticon OWN IS

Cros or Bi-Cros Systems (Contralateral routing of signal)

With Cros systems, the signal is transmitted from the deaf side to the better ear using a Bluetooth or NFMI connection. Such devices are generally used in cases of severe asymmetrical hearing loss. Bi-Cros is used when the better ear is also affected and is supported by a hearing aid. The wearer is thus able to hear/understand sound impressions and speech from the deaf side of the better ear. Nowadays, such Cros microphones look like a classic RIC system and are paired with one.

Application: Unilateral deafness due to sudden deafness, acoustic neuroma, asymmetric hearing loss

Advantages:

• Responsiveness from the deaf side
• Safety in traffic and the workplace
• Regaining spatial hearing in a reduced form

Disadvantages:

• Understanding speech in background noise often remains difficult
• Loss of spatial hearing due to not treating the worse ear
• Depending on the brand, no simultaneous audio streaming

Examples: Oticon Real Cros, Phonak Cros R, Signia Pure Cros

BAHA (Bone anchored Hearing Aid) or bone conduction hearing aids

Bone conduction systems can be used for conductive hearing loss. They are divided into transcutaneous and percutaneous systems. In both cases, an implant is placed on the temporal bone behind the ear, through which the sound impulses are transmitted to the inner ear via bone conduction. While with percutaneous systems the signal flows from the hearing system via a "screw" into the skull bone, with transcutaneous systems the signal is transmitted through the skin layer via high-frequency transmission. This drives a sound transducer attached to the mastoid from the implanted receiver. In this case, the device is magnetically anchored to the head.

Application: For conductive hearing loss or combined hearing disorders due to middle ear defects caused by otosclerosis, cholesteatoma, auditory canal dysplasia

Advantage:

• Massively improved speech intelligibility compared to conventional hearing aids, depending on the constellation

Disadvantage:

• Wind noise
• Directional hearing rather difficult
• Aesthetics
• Possible entry point for pathogens in percutaneous systems
• Poorer high-frequency transmission with transcutaneous systems

Examples: Cochlear BAHA 7, Osia 3, bone conduction hearing glasses

CI (cochlear implant)

Cochlear implants are used to transmit sound signals directly to the auditory nerve. A sound processor is worn behind the ear and is magnetically connected to the implant. They have a major impact on speech development, particularly in children who are fitted at an early age. Used for severe sensorineural hearing loss, they are also increasingly being used for adults of all ages. Namely, whenever sufficient speech understanding can no longer be guaranteed with conventional - usually HDO - systems. Cochlear implants tend to fall within the remit of ENT clinics.

Application: For severe sensorineural hearing loss

Examples: Cochlear Nucleus, Med-EL Synchrony