“Deafness” covers a wide spectrum of hearing ability, meaning the question of whether a deaf person can hear at all does not have a simple yes or no answer. Hearing loss is a measured reduction in the ability to perceive sound, ranging from difficulty hearing soft whispers to the inability to hear extremely loud noises. Many individuals classified as deaf or hard-of-hearing retain some level of residual hearing, which can often be accessed and utilized with technology. Understanding this spectrum requires examining how hearing loss is measured, its physical causes, and the tools available to enhance sound perception.
Understanding the Degrees of Hearing Loss
Hearing loss is quantified using decibels (dB), which measure the loudness required for a person to detect sound. Normal hearing is defined as detecting sounds at 15 dB or better. People are categorized as hard-of-hearing when their loss ranges from mild to severe, meaning some hearing ability is still present. Mild loss (26 to 40 dB) means a person misses soft sounds like whispering but can follow conversation in quiet environments. Moderate loss (41 to 55 dB) means normal speech sounds are often missed, requiring others to repeat themselves frequently.
Severe hearing loss (71 to 90 dB) means sounds are inaudible, requiring heavy reliance on lip-reading or amplification. Profound hearing loss is defined as not hearing sounds below 91 dB or greater. Individuals with profound loss are typically referred to as deaf because they perceive virtually no sound or only very loud vibrations. The term “hard-of-hearing” implies residual hearing is present, while “deaf” generally refers to this profound loss of auditory function.
The Physical Differences Between Types of Deafness
The physical location of the damage in the ear determines the type of sound a person perceives. Conductive hearing loss occurs when sound transmission is blocked or impaired in the outer or middle ear, preventing sound waves from reaching the inner ear. This type is often caused by temporary issues like earwax buildup, infection fluid, or a damaged eardrum. With conductive loss, sound clarity is often maintained if the volume can be sufficiently increased to bypass the blockage.
In contrast, sensorineural hearing loss (SNHL) involves damage to the inner ear, specifically the delicate hair cells within the cochlea, or the auditory nerve itself. This is the most common type and is typically permanent, resulting from factors like aging, loud noise exposure, or genetics. Because the sensory cells are damaged, increasing the volume does not restore hearing; the sound often remains distorted or muffled. A third category, mixed hearing loss, combines both conductive and sensorineural issues.
Technology That Amplifies Residual Hearing
Technology plays a major role in allowing people with hearing loss to access their residual hearing. Hearing aids are the most common solution, working by amplifying sounds to a level the damaged inner ear cells can still detect. They are effective for mild-to-severe hearing loss, capitalizing on the remaining sensory hair cells. The goal is to make soft sounds audible and normal sounds comfortable, while preventing loud sounds from becoming painful.
For people with severe-to-profound sensorineural hearing loss who receive little benefit from powerful hearing aids, cochlear implants offer a different pathway. These devices do not merely amplify sound; they bypass the damaged hair cells entirely. An external sound processor captures sound, converts it into electrical impulses, and transmits them to an electrode array surgically placed in the cochlea. This array directly stimulates the auditory nerve, allowing the brain to perceive the electrical signals as sound. While implants do not restore normal hearing, they provide access to sound and speech utilizing the remaining function of the auditory nerve.