Hearing aids are the primary intervention for addressing hearing loss by utilizing amplification to make sounds audible. However, for some individuals, these devices eventually fail to provide adequate clarity or volume. This limitation signals that the underlying hearing damage has progressed beyond what simple sound amplification can effectively manage. When this happens, it is necessary to explore more advanced technological and surgical options to restore communication ability.
Recognizing the Limits of Amplification
The limitations of traditional amplification become apparent when an audiogram reveals hearing thresholds in the severe or profound range. Severe hearing loss is defined by thresholds between 71 and 95 decibels (dB), while profound loss exceeds 95 dB. At these levels, devices must significantly increase sound volume, which often fails to improve speech understanding.
The fundamental issue is that hearing loss is primarily a problem of clarity, not just volume. Sensorineural hearing loss, the most common type, involves damage to the delicate hair cells in the inner ear. These cells convert sound vibrations into electrical signals, and when damaged, they cannot process sound effectively. Simply increasing the volume results in distorted or unclear sound because the inner ear structures are too damaged to process the signal.
This distinction between loudness and clarity is reflected in the common complaint: “I can hear you, but I cannot understand you.” The inner ear loses its ability to resolve the fine details of sound, particularly the high-frequency consonants that convey speech information. An audiologist evaluates the lack of benefit from hearing aids through specific speech recognition tests to determine when a patient has reached the limits of amplification.
Surgical Options for Severe Hearing Loss
When hearing aids cease to provide sufficient benefit, surgical interventions offer alternative methods for delivering sound information to the auditory system. Cochlear Implants and Bone-Anchored Hearing Systems address different underlying causes of hearing loss.
Cochlear Implants (CI)
Cochlear implants (CI) are sophisticated electronic devices designed to restore functional hearing for individuals with severe to profound sensorineural hearing loss. Unlike hearing aids, a CI bypasses the damaged parts of the inner ear entirely. The external sound processor captures sound and converts it into digital signals.
These signals are then transmitted to an internal receiver/stimulator that is surgically placed under the skin behind the ear. The receiver sends electrical impulses directly to an electrode array threaded into the cochlea, stimulating the auditory nerve. Candidacy requires a diagnosis of bilateral severe to profound sensorineural hearing loss and demonstration of limited speech understanding benefit from appropriately fitted hearing aids. For adults, this limited benefit is often defined by scoring 50% or poorer on sentence recognition tests in the ear to be implanted.
Bone-Anchored Hearing Systems (BAHS)
Bone-Anchored Hearing Systems (BAHS), sometimes referred to as Bone-Anchored Hearing Aids (BAHA), provide a solution for hearing loss rooted in the outer or middle ear. This technology is indicated for conductive hearing loss, mixed hearing loss, or single-sided deafness where traditional air-conduction hearing aids are ineffective. Conductive loss occurs when sound waves are blocked from reaching the inner ear due to issues like chronic ear infections or ear canal malformations.
A BAHS works by using bone conduction to transmit sound vibrations directly to the functioning inner ear, bypassing the problematic outer and middle ear structures. The system uses an external sound processor that converts sound into vibrations. These vibrations are then transferred via a small abutment or magnetic plate surgically implanted into the skull bone behind the ear. This direct stimulation of the cochlea sends the sound signal to the brain.
Specialized Assistive Listening Technology
For many individuals, certain environments pose significant listening challenges due to distance, background noise, or poor room acoustics. Specialized Assistive Listening Technology (ALT) is designed to improve the signal-to-noise ratio in these difficult situations. ALT systems work in conjunction with existing devices, delivering a cleaner, more direct audio signal than the device microphone can capture alone.
FM and Digital Modulation (DM) systems use radio frequency transmission to send sound directly to a receiver worn by the listener. The speaker wears a microphone, and the sound is broadcast wirelessly, eliminating the negative effects of distance and background noise on speech clarity. These systems are frequently used in classrooms, lecture halls, or one-on-one conversations where a direct signal from the speaker is needed.
Telecoils, or T-coils, are small copper wires built into many hearing aids and cochlear implants that function as miniature wireless receivers. They pick up electromagnetic signals generated by hearing loop systems installed in public spaces like theaters and churches. When activated, the T-coil streams sound from the venue’s public address system directly into the hearing device, bypassing room acoustics and environmental noise.
Specialized alerting devices address safety and daily living needs by utilizing visual or tactile signals instead of sound. These devices provide necessary alerts that a person with hearing loss might miss, ensuring safety and independence in the home environment. Examples include alarm clocks that use light flashes or bed shakers, doorbells that flash lamps, and smoke detectors that use strobes or vibration.