What is an audiogram and how is it used to diagnose and manage hearing loss in adults?

What is an Audiogram and How to Use It

Definition and Purpose

An audiogram is a graph that displays the results of pure tone audiometry (PTA), which is the gold standard test for measuring hearing sensitivity across different sound frequencies and volumes. 1 The test measures your ability to hear sounds through two pathways: air conduction (through the ear canal) and bone conduction (through skull vibration), allowing clinicians to determine the type, degree, and pattern of hearing loss. 1

How to Read an Audiogram

The Graph Structure

• X-axis (horizontal): Shows sound frequencies measured in Hertz (Hz), typically ranging from 250 to 8000 Hz 1

  • Lower frequencies (250-500 Hz) = deeper sounds like a bass drum
  • Mid frequencies (500-4000 Hz) = speech sounds, the most critical range for understanding conversation 1, 2
  • Higher frequencies (4000-8000 Hz) = high-pitched sounds like birds chirping

• Y-axis (vertical): Shows sound intensity measured in decibels (dB), ranging from -10 to 120 dB 1

  • The numbers increase going DOWN the graph (counterintuitive but standard)
  • Lower numbers = softer sounds
  • Higher numbers = louder sounds needed to hear

Symbols and Lines

• O or red line: Right ear air conduction 3
• X or blue line: Left ear air conduction 3
• < or [: Bone conduction symbols (used to distinguish conductive from sensorineural hearing loss) 1

Interpreting Hearing Loss Severity

Normal vs. Abnormal Hearing

• Normal hearing: Thresholds ≤20 dB across all frequencies 1, 2
• Mild hearing loss: 21-40 dB 2
• Moderate hearing loss: 41-55 dB 2
• Moderately severe hearing loss: 56-70 dB 2
• Severe hearing loss: 71-90 dB 2
• Profound hearing loss: >90 dB 2

Types of Hearing Loss Identified

The audiogram distinguishes three types by comparing air and bone conduction results: 1, 3

1. Sensorineural hearing loss: Both air and bone conduction thresholds are equally reduced (lines overlap), indicating inner ear or nerve damage 1

2. Conductive hearing loss: Bone conduction is normal but air conduction is reduced (gap between lines), indicating outer or middle ear problems 1

3. Mixed hearing loss: Both pathways are affected but air conduction is worse than bone conduction 1

Components of a Comprehensive Audiometric Evaluation

A complete hearing assessment should include more than just the audiogram: 1

• Pure tone thresholds: Measured at 250,500,1000,2000,3000,4000,6000, and 8000 Hz 1
• Speech audiometry: Tests your ability to understand words, not just hear tones 1
  • Speech recognition threshold (SRT): Softest level you can understand speech
  • Word recognition score (WRS): Percentage of words correctly identified at comfortable volume
• Tympanometry: Assesses middle ear function and eardrum mobility 1
• Acoustic reflex testing: Evaluates neural pathways 1, 2
• Otoacoustic emissions (OAE): Measures inner ear (cochlear) function 1, 4

Critical Red Flags Requiring Specialist Referral

You must refer patients to an otolaryngologist when the audiogram shows: 1, 4

• Asymmetric hearing loss: Difference >15 dB between ears in pure tone average OR >15% difference in word recognition scores 4, 5
• Conductive or mixed hearing loss: Suggests treatable middle ear pathology 1
• Poor word recognition scores: Disproportionately low compared to pure tone thresholds, suggesting retrocochlear pathology 1, 5
• Sudden hearing loss: Requires urgent evaluation and possible corticosteroid treatment within 2 weeks 1, 5

Common Pitfalls to Avoid

• Don't rely on tuning fork tests alone: They lack sufficient accuracy for clinical decision-making 4
• Don't ignore small changes: Standard test-retest variability is ±5 dB, so changes <10 dB may not represent true hearing loss progression 2
• Don't assume the audiogram tells the whole story: Patients may have normal audiograms but still experience hearing difficulties in noisy environments, requiring central auditory processing evaluation 3
• Don't forget that physicians struggle with interpretation: Studies show primary care physicians score only 4/9 on audiogram interpretation tests, so consider supplementing with written explanations 6

Access and Alternative Testing Options

Limitations of Standard Audiometry

• 56.6% of US counties lack access to audiologists, disproportionately affecting lower-income and older adults 1
• Older adults with cognitive dysfunction may have difficulty completing testing 1
• Cost barriers exist as Medicare Parts A and B don't cover hearing aids 7

Alternative Screening Methods

When comprehensive audiometry is unavailable, consider: 1

• Handheld audiometers: Quick in-office screening at 500,1000,2000, and 4000 Hz with >20 dB threshold indicating referral need 1
• Self-administered questionnaires: Can identify perceived hearing difficulty but don't replace objective testing 1
• Smartphone apps: Moderate evidence quality for screening but require calibration 1, 8

However, any positive screen must be confirmed with a comprehensive pure tone audiogram before treatment decisions, especially before fitting hearing aids. 1, 7