Sensorineural hearing loss is diagnosed primarily through a hearing test called pure tone audiometry, which compares how well you hear sounds delivered through the air versus directly through the bone behind your ear. When both pathways show the same degree of loss (within 10 dB of each other), the problem is in the inner ear or auditory nerve rather than the outer or middle ear. The full diagnostic process typically involves several tests layered together to confirm the type of loss, measure its severity, and identify a possible cause.
The Physical Exam and Tuning Fork Tests
Before any formal hearing test, a clinician examines your ears to rule out obvious causes like earwax blockage, fluid behind the eardrum, or infection. This step matters because those problems cause conductive hearing loss, which can mimic or overlap with sensorineural loss.
Two quick bedside tests using a tuning fork help point toward the right diagnosis. In the Weber test, a vibrating tuning fork is placed on the center of your forehead. If you have sensorineural loss in one ear, the sound will seem louder in your better ear. In the Rinne test, the fork is held next to your ear and then pressed against the bone behind it. With sensorineural loss, you’ll still hear the airborne sound longer than the bone sound (a normal pattern), but both will be quieter on the affected side. These tests take under a minute and give the clinician an immediate sense of whether the loss is sensorineural or conductive before sending you for more detailed testing.
Pure Tone Audiometry
This is the cornerstone of diagnosis. You sit in a soundproof booth wearing headphones, and an audiologist plays tones at different pitches and volumes. Each time you hear a tone, you press a button or raise your hand. This measures your air conduction thresholds, the quietest sounds you can detect at each frequency.
Next, the audiologist places a small vibrating device on the bone behind your ear. This sends sound directly to your inner ear, bypassing the eardrum and middle ear bones entirely. These are your bone conduction thresholds. Comparing the two sets of results is what clinches the diagnosis: if air and bone conduction thresholds are both elevated and fall within 10 dB of each other, the loss is sensorineural. If bone conduction is normal but air conduction is reduced (a gap of 15 dB or more), the problem is conductive. Some people have both, which is called mixed hearing loss.
The results are plotted on an audiogram, a graph showing your hearing ability across frequencies from low (250 Hz) to high (8,000 Hz). The World Health Organization classifies severity based on the average threshold across key frequencies: 26 to 40 dB is slight, 41 to 60 dB is moderate, 61 to 80 dB is severe, and 81 dB or greater is profound. At the slight end, you can still follow normal conversation. At the profound end, even shouting is inaudible without amplification.
Speech Recognition Testing
Pure tone audiometry tells you how loud a sound needs to be for you to detect it, but it doesn’t capture how clearly you understand speech. That’s a separate problem, and it’s often the complaint that brings people in: “I can hear people talking, I just can’t make out the words.”
In a word recognition test, you listen to a list of single-syllable words played at a volume loud enough for you to hear them, then repeat each one back. The percentage you get right is your word recognition score. A score that’s lower than expected based on your audiogram suggests the damage goes beyond simple volume loss. The gap between predicted and measured scores tends to be largest in conditions that damage auditory nerve fibers directly, such as Ménière’s disease, sudden hearing loss, and auditory neuropathy. It’s smaller in age-related hearing loss. This distinction helps the audiologist understand not just how much hearing you’ve lost, but where the damage sits and how well a hearing aid is likely to help.
Otoacoustic Emissions Testing
Your inner ear doesn’t just receive sound. It also produces faint sounds of its own, generated by tiny structures called outer hair cells as they amplify incoming signals. An otoacoustic emissions (OAE) test picks up these sounds using a small microphone placed in your ear canal. If the emissions are present, your outer hair cells are working normally. If they’re absent or reduced, those cells are damaged.
This test is especially useful for narrowing down the site of injury. Someone with absent OAEs and abnormal audiometry likely has damage to the outer hair cells themselves, the most common pattern in noise-induced and age-related hearing loss. Someone with normal OAEs but poor hearing may have a problem further along the pathway, in the inner hair cells or auditory nerve. OAE testing can also detect early damage from noise exposure or certain medications before it shows up on a standard audiogram, making it a valuable monitoring tool for people at risk.
Auditory Brainstem Response Testing
An auditory brainstem response (ABR) test measures the electrical signals that travel from your auditory nerve through the brainstem when sound enters your ear. Small electrodes are placed on your scalp, clicks or tones are played through earphones, and a computer records the neural response. You don’t need to press any buttons or respond at all, which makes ABR the gold standard for testing infants who fail their newborn hearing screen.
ABR is also used for adults who can’t complete standard audiometry reliably, and for anyone whose results suggest a problem beyond the inner ear. In auditory neuropathy spectrum disorder, for example, outer hair cell function is normal (OAEs are present) but the ABR is absent or severely abnormal, confirming that the dysfunction lies in the connection between the inner hair cells and the auditory nerve. ABR is not routinely needed when standard audiometry gives clear, consistent results.
When Imaging Is Needed
Most sensorineural hearing loss doesn’t require a scan. The exception is asymmetric loss, where one ear is significantly worse than the other, because this pattern raises concern for a benign tumor on the hearing nerve called a vestibular schwannoma (acoustic neuroma). An MRI of the internal auditory canals is the standard imaging test in these cases. Research published in JAMA Otolaryngology found that asymmetry of 15 dB or more at 3,000 Hz was associated with a higher likelihood of finding an abnormality on MRI. The presence of one-sided tinnitus, dizziness, or numbness in the face further increases that concern.
CT scans are sometimes used when MRI isn’t available or when the clinician suspects a structural abnormality of the inner ear, particularly in children with congenital hearing loss.
Blood Tests for Underlying Causes
Sensorineural hearing loss has many possible causes, and blood work can help identify treatable ones. A systematic review of biomarkers in sudden sensorineural hearing loss found that elevated inflammatory markers are nearly universal, suggesting that inflammation or autoimmune activity plays a role in many cases. The most useful routine tests were a complete blood count and a clotting screen (specifically fibrinogen levels), both inexpensive and widely available.
Beyond those baseline tests, clinicians may check for specific conditions on a case-by-case basis: thyroid function, blood sugar levels to screen for diabetes, syphilis serology, or markers of autoimmune inner ear disease. These aren’t ordered for everyone with hearing loss but are targeted when the pattern of loss, the patient’s age, or other symptoms suggest an underlying systemic condition.
Diagnosing Sudden Sensorineural Hearing Loss
Sudden sensorineural hearing loss is defined as a drop of 30 dB or more across three consecutive frequencies, developing over hours to days. It’s considered a medical urgency. The diagnostic criteria come from the American Academy of Otolaryngology’s clinical practice guideline, which notes that clinicians may also investigate cases with less than 30 dB of loss when the onset is rapid and symptoms are concerning.
The workup for sudden loss follows the same testing sequence described above, but with greater urgency. Audiometry is performed immediately to confirm the type and degree of loss, and MRI is typically ordered to rule out a tumor or stroke affecting the hearing pathways. Blood work is more likely to be included upfront, since identifying an inflammatory or vascular cause can change the treatment approach. The key distinction from gradual hearing loss is timing: the faster the diagnosis, the better the chance that treatment can recover some hearing.