What are AMPLIFICATION DEVICES?
The purpose of an AMPLIFICATION DEVICE is to amplify sound to overcome a hearing loss. The hearing aid is a miniature sound system that combines a microphone, amplifier, and output transducer (termed the receiver by analogy with a telephone handset). M hearing aids available today use digital technology to process the sound, and incorporate algorithms designed to take into account the characteristics of the desired signals (e.g., speech or music) and the properties of the impaired auditory system.
HEARING AIDS
The function of hearing aids is to amplify sounds to a degree and in a manner that will enable a person with hearing impairment to use his or her remaining hearing in an effective manner.
Body Hearing Aids
Body hearing aids contain all of their components and controls (except for the receiver and earmold) in a case about the size of a small pocket calculator. A wire leads from the case to the receiver and earmold at the patient’s ear. The case is usually worn somewhere on the chest. Typical locations are in a chest-level pocket; clipped to a shirt, jacket, or undergarment; or in a specially made harness.
Body aids, as you might guess from the name, are worn on the body. They are relatively large and include a box-like case that contains the microphone and amplification stages; a receiver is worn in the ear and is attached to the case by a cord. Access to the hearing aid battery and user controls, including the volume control wheel and the on and off switch, are provided on the case surface, usually on the top and/ or bottom.
Eyeglass BTEs
The microphone, amplifier, and receiver are built into the eyeglass temples (side pieces) . The receiver output goes through a plastic tube to an earmold in the patient’s ear. They are similar to BTE models for range of hearing loss fitted and flexibility of adjustment. They are similar to BTE models for range of hearing loss fitted and flexibility of adjustment.
Behind-the-ear (BTE)
“Conventional” Hearing aids are identified as BTE (over-the-ear, Post auricular) hearing aids and are designed to fit behind the pinna. Devices are encased in plastic and curved to match their placement behind the pinna. They are heavy-duty, provide wide selection of amplification characteristics, and fit a range of hearing losses from mild to profound. The microphone(s) is/are placed at the top of the aid near the upper portion of the ear to take advantage of the head shadow effect and to approximate sound entry into the ear canal.
Receiver-In-The-Ear (RITE)
Receiver in Canal (RIC) consists of a small device placed behind the ear and a speaker or receiver that sits inside the ear canal. RIC hearing aids are popular due to their discreet appearance and comfortable fit. The receiver in the canal design allows for a more natural sound experience as the receiver is placed closer to the eardrum, resulting in improved sound quality and reduced feedback or whistling. It also allows for better localization of sound and improved speech understanding in noisy environments.
In The Canal ITC
Hearing aids that fill the entire concha are referred to as in-the-ear. The size of these instruments is between the CIC and the in-the-car (ITE) hearing aid. The aid fits within the concha and the cartilaginous portion of the ear canal, with the microphone opening located at the outer portion of the concha. In-the-canal devices are easy to insert, easy to remove, and easy on your eyewear. Because they fit entirely in the ear canal, these devices won’t interfere with glasses, hats, or other headwear. And because they are custom molded just for your unique ear shape, they stay put — even when you’re on the move.
IN THE EAR ITE
First developed in the late 1950s, instruments that are worn entirely in the concha and external auditory canal with the circuitry built into the earmold itself are still the most prevalent of the hearing aid styles worn within the ear. Originally useful only for mild hearing losses, they can now be used for hearing losses that range from mild to moderately severe because of improved technology.
COMPLETELY IN THE CANAL HEARING AIDS
Completely-in-the-canal, or CIC, hearing aids are custom hearing aids in which all components fit into the ear canal only. Initially designed to address primarily high-frequency hearing loss, their main benefits were considered to be cosmetic and in reducing the occlusion effect, or the perception that the ear feels plugged, as reported by many wearers, particularly those with high frequency hearing loss. The CIC style addresses many issues that kept individuals from being previously successful with hearing aids, including the reduction of wind noise (important for sports or working outside) and the ability to use the hearing aids comfortably without feedback on the telephone or with a stethoscope. Because the components of this hearing aid are closer to the eardrum, less electronic gain is required compared to other styles, which also reduces the risk of acoustic feedback.
CROS Hearing Aids
CROS is known as contralateral routing of offside signals first described by Harford and Barry in 1965 as a specially built instrument for patients with an unaidable unilateral hearing loss has a particular kind of listening difficulty, which can include trouble hearing soft speech from the “bad side.” In this configuration, the microphone is mounted on the side of the impaired ear, and the signal is sent to the amplifier and receiver fitted at the side of the normal-hearing ear. The signal may be routed electrically through wires that are draped behind the head for BTE and ITE aids.
CROS Hearing Aid Solution
- the CROS aid with a microphone picks up sounds and voices from the non-hearing ear and
- wirelessly transmits them to the hearing aid
- the normal ear with a hearing aid receives the signal from the non-hearing ear and plays it to
- your good ear
- enables you to have a conversation in quiet and noisy surroundings without having to
- reposition yourself
- allows you to respond to friends when they talk to you on the side you can’t hear from
- requires no surgical procedures
- wear it without it being noticed
- comes in a variety of technologies to fit your budget
Bi-CROS
A BiCROS hearing aid configuration allows for implementation of the traditional CROS principle, with the addition of amplification delivered directly to the better-hearing ear when this ear also has some degree of hearing loss.
BiCROS Hearing Aid Solution
- the BiCROS system will pick up sounds in the non-hearing ear and wirelessly transmit the sound to the better ear, while also amplifying sound to the better ear
- enables you to have a conversation in quiet and noisy surroundings without having to reposition yourself
- allows you to respond to friends when they talk to you on the side you can’t hear from
- requires no surgical procedures
- wear it without it being noticed
- comes in a variety of technologies to fit your budget
Bone-Conduction Hearing Aids
Bone-conduction hearing aids are selected for those patients with conductive hearing loss and otological conditions that preclude the use of air-conduction amplification. These conditions may include persistent or recurrent ear drainage or hearing loss resulting from congenital ear canal anomalies. The transducer is a vibrating receiver that is pressed firmly against the mastoid process. As vibration of the skull stimulates both cochleas from a single bone-conduction instrument, true binaural hearing, arising from timing and intensity differences of sounds reaching the two ears, is not attainable. Less than half a percent of all hearing aids prescribed are bone-conduction hearing aids.
Bone Anchored Hearing Aid
The bone anchored hearing aid, or BAHA, is an implantable hearing aid designed to address conductive hearing loss, mixed hearing loss, or single-sided deafness (SSD). The BAHA uses the concept of bone conduction, or how sound is delivered to the inner ear by vibration of the bones in the skull. The BAHA system bypasses the middle ear system and delivers the sound signal directly to the inner ear. A titanium abutment, or screw, is surgically implanted in the bone of the skull behind the ear. An external sound processor is used that is attached to the abutment. The processor allows for the sound to be picked up and delivered directly to the inner ear. The BAHA can be safely implanted in both children and adults. BAHA users have been found to have significantly better speech understanding ability than with traditional bone conduction hearing aids and also improved ability to hear in the presence of background noise. Just as with hearing aids, the BAHA is designed with consideration to how listeners live their lives, including an adapter to connect an MP3 player or cell phone directly to the processor
Middle-Ear Implants
The impetus behind the development of middle-ear implants has been improved fidelity by driving the ossicles and/or cochlea directly without occlusion of the outer ear and reduction of acoustic feedback (because the energy is not transduced back to an acoustic signal). Designed primarily for moderate to severe sensory/neural hearing loss, these devices are increasingly being used with mixed hearing loss as well. This implanted device consists of three components: (1) an external audio processor that transmits sound across the skin to (2) an implanted receiver, which in turn transmits the converted electrical signal to (3) a transducer mounted onto the ossicular chain. Later-developed fully implantable middle-ear hearing prosthetics (Bassim & Fayed, 2010), like partially implanted devices, appeal to some patients because of their reported advantages of improved sound clarity, reduced feedback, and the elimination of the occlusion effect.
Cochlear Implants
The cochlear implant allows for direct stimulation of the auditory nerves. The internal receiver, which is implanted under the skin behind the pinna, consists of wire electrodes and a tiny coil. Up to 22 active electrodes are placed 22 to 24 mm into the scala tympani within the cochlea. Ground electrodes are placed outside the bony labyrinth, often in the temporalis muscle. A small microphone attached to an earhook feeds electrical impulses to a speech processor housed in a behind-the-ear casing, or a body-worn unit similar to a body-style hearing aid. The processor codes the speech information, which is subsequently delivered to a transmitter, which in turn converts it to magnetic impulses that are transmitted to the electrode array. An electrical signal is induced from the magnetic field in the cochlea and flows on to stimulate the auditory nerve.
AUDITORY BRAINSTEM IMPLANT (ABI)
This device, with the electrode array implanted directly into the brainstem, is designed to address neural pathologies of the auditory system, such as those that occur in neurofibromatosis type 2 (NF2). Individuals with this type of hearing loss generally have no residual hearing ability and demonstrate no ability to make use of auditory information, often relying primarily on speech reading. The first ABI surgery was performed in 1979 . Analogous to the fact that the cochlear implant replaces a damaged portion of the auditory system, the ABI bypasses the damaged auditory nerve and is implanted directly into the brainstem.
Treating your hearing loss is the first step toward a healthier, happier life.
Wearing a hearing aid can enrich your life and reopen many doors that may have closed for you over the years. Other benefits of treating your hearing loss with hearing aids include:
- Hearing your grandchild's first words
- Hearing nature again
- Feeling safer in cities
- Attending dinners in noisy environments
- Enjoying parties and understanding conversation