Hearing Loss Types and Degrees Explained (2025 Guide)
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The 4 Types of Hearing Loss
Hearing loss is classified by where in the auditory system the damage occurs — not by how much hearing is lost. Understanding the type determines which treatments work.
Sensorineural Hearing Loss — Most Common in Adults
Sensorineural hearing loss results from damage to the hair cells in the cochlea or the auditory nerve connecting the cochlea to the brain. It accounts for approximately 90% of all adult hearing loss cases (NIDCD, 2024).
- Cause: Age-related degeneration (presbycusis), noise exposure, genetics, certain medications (ototoxic drugs), viral infections
- Characteristics: Permanent in most cases; sounds may be audible but unclear, especially consonants
- Treatment: Hearing aids are the primary treatment; cochlear implants for severe-to-profound cases where aids provide insufficient benefit
- What it sounds like: Speech sounds muffled; high-pitched sounds (birds, phone ringtones) disappear first
Conductive Hearing Loss — Usually Temporary
Conductive hearing loss occurs when sound cannot efficiently travel through the outer or middle ear to reach the cochlea. The inner ear itself is typically unaffected.
- Cause: Earwax blockage, ear infections (otitis media), perforated eardrum, fluid in the middle ear, otosclerosis (abnormal bone growth)
- Characteristics: Often temporary and treatable; sounds are reduced in volume but remain clear
- Treatment: Medical or surgical treatment of the underlying cause; hearing aids if surgery is not appropriate
- What it sounds like: Everything sounds quieter, like hearing through earplugs or cotton wool
Mixed Hearing Loss
Mixed hearing loss involves both sensorineural and conductive components — damage to both the inner ear/auditory nerve and the outer/middle ear pathway.
- Cause: Any combination of the above causes occurring simultaneously
- Treatment: Addresses the conductive component medically first; hearing aids for the remaining sensorineural component
- Prevalence: Less common than pure sensorineural; more common in older adults with age-related inner ear loss plus recurring ear infections
Auditory Neuropathy Spectrum Disorder (ANSD)
ANSD occurs when sound enters the cochlea normally but the auditory nerve fails to transmit signals to the brain reliably. Standard hearing tests may show normal results while the person experiences significant difficulty understanding speech.
- Cause: Damage to inner hair cells, auditory nerve, or brainstem auditory pathways; associated with premature birth, jaundice, genetic factors
- Characteristics: Normal or near-normal pure-tone audiogram but severely impaired speech understanding; inconsistent day-to-day hearing
- Treatment: Cochlear implants show strong outcomes; hearing aids provide variable benefit
- Diagnosis: Requires ABR (auditory brainstem response) testing beyond a standard audiogram
The 5 Degrees of Hearing Loss
Degree of hearing loss is measured in decibels (dB HL) — the softest sound a person can hear at each frequency. Normal hearing is defined as the ability to detect sounds at 0–25 dB HL.
| Degree | Threshold | What You Struggle to Hear | Typical Treatment |
|---|---|---|---|
| Normal | 0–25 dB | Nothing significant | No treatment needed |
| Mild | 26–40 dB | Soft speech, whispers, distant conversation | OTC hearing aids; optional audiologist |
| Moderate | 41–55 dB | Normal conversation, especially in noise | Prescription or OTC hearing aids |
| Moderate-Severe | 56–70 dB | Most speech without aids | Prescription hearing aids required |
| Severe | 71–90 dB | Loud speech, shouted conversation | Powerful hearing aids or cochlear implant evaluation |
| Profound | 91+ dB | Almost no hearing without amplification | Cochlear implants often most effective option |
How Degrees Are Measured
An audiologist plots your hearing thresholds at 6–8 frequencies (250–8,000 Hz) on an audiogram — a graph with frequency on the horizontal axis and volume (dB) on the vertical axis. Your “degree” is typically based on the average of thresholds at 500, 1,000, 2,000, and 4,000 Hz — the frequencies most critical for understanding speech.
Mild loss often goes undetected for years because the brain compensates — increasing listening effort rather than triggering obvious awareness of hearing difficulty. The average person waits 7 years from first noticing hearing difficulty to seeking treatment (HLAA).
How Type and Degree Interact
The same degree of hearing loss can have different implications depending on the type:
- Mild sensorineural loss: Permanent; OTC or prescription aids appropriate
- Mild conductive loss: Often temporary and reversible with treatment of the underlying cause
- Mild mixed loss: Treat the conductive component first; reassess degree afterward
- Moderate sensorineural loss: Prescription aids with audiologist fitting produce best outcomes
- Severe sensorineural loss: Cochlear implant evaluation warranted if aids provide insufficient benefit
