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Information

Editors

JukkaKokkonen

Assistive Devices for People with Hearing Impairment

Essentials

  • Medical rehabilitation and assessment of the need for such rehabilitation may be free of charge for patients.
  • Adults should be referred for assessment of the need for rehabilitation if the mean better ear hearing level over the frequencies 500-4000 Hz (BEHL0.5-4kHz) is 30 dB or worse.
  • In children, mere suspicion of a hearing defect is sufficient for referral.
  • If the hearing defect is so severe that hearing aids do not help sufficiently, a cochlear implant should be considered.
  • Notice that there may be differences in the local policies and practices concerning the utilization and reimbursement of hearing aids and other assistive devices for hearing impairment. Hence, check also local guidelines.

Regulations

  • Find out whether the following services, for example, are free of charge for patients in your country:
    • Guidance associated with technical rehabilitation
    • Assessment of the need and possibilities for rehabilitation
    • Defining the need for aids, fitting of aids, providing the patient with aids to remain in their possession or on loan, teaching them how to use the aids, follow-up of use, and maintenance of aids.

Estimated need for hearing rehabilitation

  • It has been estimated that in the Nordic countries and in Great Britain 20% of the population have a hearing defect of more than 25 dB and 5% have a defect of more than 45 dB over the frequencies 0.5 to 4 kHz.
  • Utilization of hearing aids varies across countries.
    • In Finland, not more than approximately 1% of the population have a hearing aid, whereas in other Nordic countries and in Great Britain the respective figure is 2.3-3.5%. According to the prevalence of hearing defects, 5% of the population would be in need of hearing rehabilitation even if rather strict criteria were applied.
  • Along with the ageing of the population the need will increase.

Hearing aids

Types of hearing aids

  • Behind-the-ear hearing aids are the most common type. Behind-the-ear hearing aids with custom-made, tight earpieces are more suitable for severe hearing defects than other types of hearing aids. In mild to moderately severe hearing defects Interpretation of an Audiogram and Impaired Hearing, the earpiece may be of the open type, which increases listening comfort. Behind-the-ear hearing aids can be divided into the following types:
    • Hearing aids with earpiece. The sound is conducted from the hearing aid behind the ear via a tube and a custom-made earpiece into the ear canal. Such aids are easier to handle, even by people with reduced finger dexterity, than the types of hearing aids described below.
    • Slim tube hearing aids. The sound is led into the ear canal via a slim tube and usually a loose-fitting dome that is not custom-made. This type of aid requires relatively good hearing at low frequencies.
    • Receiver-in-canal hearing aids. There is no sound tube but a wire, and the sound is produced in a receiver situated in the ear canal.
  • In-the-canal hearing aids. The hearing aid apparatus is inside a custom-made shell. Depending on the size of the ear canal, the apparatus may be situated completely in the canal (CIC) or partly in the bowl-shaped area of the outer ear (concha hearing aids). Today, open fit behind-the-ear hearing aids have largely replaced in-the-canal hearing aids.
  • Bone conduction hearing aids. If the patient has ear canal atresia (missing ear canal) or chronic middle ear infection with discharge from the ear, the sound can be conducted to the inner ear as vibration through the skull.
    • Headband hearing aids, where a stretchable fabric band or spring presses the vibrator tight against the skull.
    • Bone-anchored hearing devices, where the vibration is conducted to the skull through a titanium screw attached to the temporal bone.
  • Hearing aids in current use are based on digital signal processing. The device is individually adjusted according to the hearing of the patient, and all devices, in practice, are adaptive, i.e. their action is automatically altered according to the ambient auditory environment.
  • Using a hearing device always requires practice. Careful fitting and instruction decrease the share of unused devices. Adjusting to the new auditory world conveyed by the device may often take several months.

Other assistive devices

Communication amplifiers

  • Suited particularly for people for whom ordinary hearing aids are motorically too challenging or too complicated.
  • Used instead of a hearing aid to amplify speech and environmental sounds.

Cochlear and brainstem implants

  • Cochlear implants are hearing instruments for profoundly impaired hearing. The instrument transmits an electric signal directly to the cochlear nerve by-passing the nonfunctioning inner ear.
  • Cochlear implants may be considered for both postlingually deaf children or adults and congenitally or prelingually deaf children. Prelingually deaf adults are not suitable for implant candidates.
  • After implantation, the device has to be programmed individually and hearing must be trained. Prelingually deaf children need the same kind of hearing rehabilitation as other children with hearing impairment.
  • The implantees need follow-up for the rest of their lives.
  • If the cochlear nerve is not functioning (due to, e.g., bilateral acoustic neurinoma or injury), the electric signal may be transmitted to the brain stem auditory nuclei (brainstem implant).

Alarm aids

  • Alarm equipment, such as alarm clocks, telephone or doorbell alarms, fire alarms and cry alarms may be either separate aids or linked to an alarm centre. Light indicators, vibration or acoustic signals can be used to raise the alarm.

Entertainment electronics, inductive listening

  • Accessory head or earphones
    • In addition to wired head- or earphones, wireless infrared earphones also exist; some infrared devices produce an acoustic signal and some an inductive signal to be received with the person's hearing aid in the T position.
  • For example, a portable induction loop to be attached to an accessory output of a radio or a television, or a loop with its own amplifier installed in the room (to be used with the hearing aid switch in the T position)
  • Many hearing aids can be wirelessly connected to accessory devices (e.g. through Bluetooth).
  • Induction loops are often available in public buildings (churches, meeting rooms, theatres) and many service facilities (social insurance offices, banks, pharmacies, etc.). They should also be installed in health care institutions, for instance. If a fixed induction loop is installed in a public space, there should be a visible sign to inform the visitors about it.
  • Auracast™ broadcast audio for public spaces, based on Bluetooth technology, is being developed but it is not believed that it will replace inductive technology within the next few years.

Group listening devices

  • A separate microphone, nowadays usually using radiofrequency transmission. The microphone is brought closer to the speaker so as to improve signal-noise ratio.
  • So-called FM devices in schools: the teacher has a microphone that employs radio frequencies to transmit the teacher's speech to a receiver that is connected to the hearing aid of the pupil.
  • Similar technology can be utilized in meetings; a microphone placed at the centre of the table, for example, can make it easier to follow the discussion.

Indications for hearing aid assessment

  • Technical hearing rehabilitation should be considered within specialized care if the better ear hearing level, measured in a sound-proof testing booth, over the frequencies 0.5-4 kHz (BEHL0.5-4kHz) is 30 dB or worse. In children, the corresponding limit is 20 dB. The goal in hearing rehabilitation with hearing aids is binaural listening, i.e., both ears should be fitted with hearing aids as a rule. Check also local recommendations and policies.
  • When assessing the need for aids, the motivation of the patient and his/her social needs, etc. should always be considered. Note that hearing impairment in an elderly person living alone, for example, may for its part result in social isolation.
  • Hearing aid assessment is one of the tasks for which hearing centres and stations are responsible. Assessment of the need for and selection of the hearing aid and assistive listening devices may require home or workplace visits.

Systems of aid payment

  • Check local policies and practices on who is responsible for reimbursement of the costs of hearing aids and other assistive devices related to hearing.
    • Different parties may be completely or partly responsible for the reimbursement of hearing defect rehabilitation, including municipalities, the health insurance system and other insurance institutions, the social services, employers, or the labour administration, taking also into account the source of the hearing problem (including, for example, military injuries, occupational diseases, traffic injuries, etc.).
  • Regardless of who pays the costs, hearing aid assessment is something where, based on the hearing impairment, the patient's other medical problems, the social situation, etc., a rehabilitation plan should be made for technical rehabilitation of hearing impairment. The next step is to find out who pays for the aid and how it is to be acquired. Hearing centres and stations are responsible for writing such rehabilitation plans.

Indications for referral for hearing aid assessment

  • Summary
    • In a child, the better ear hearing level over the frequencies 0.5-4 kHz (BEHL0.5-4kHz) worse than 20 dB.
    • If a child is suspected to have a hearing impairment but a reliable hearing test is not feasible, he/she has to be referred to specialized care for investigations.
    • In an adult, a better ear hearing level over the frequencies 0.5-4 kHz (BEHL0.5-4kHz) which is 30 dB or worse.
  • Ask about the patient's problems. Record them in the referral; this helps a lot in most cases when writing the rehabilitation plan.
  • Before drawing up the referral, make sure that the patient is sufficiently motivated for hearing aid experimentation.