What does a dip from 1000 Hz to 2000 Hz on an audiogram indicate?

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Last updated: November 13, 2026 • View editorial policy

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What Does a Dip from 1000 Hz to 2000 Hz Mean on an Audiogram?

A dip in bone conduction thresholds from 1000 Hz to 2000 Hz most commonly indicates conductive hearing loss, particularly from middle ear pathology such as ossicular fixation (especially stapes fixation) or middle ear effusion (glue ear). The specific pattern and location of the dip help distinguish between different underlying pathologies.

Clinical Significance of the Dip Pattern

The 2000 Hz Dip (Carhart Notch)

A dip specifically at 2000 Hz in the bone conduction audiogram is known as a Carhart notch and has strong clinical predictive value:

  • Ossicular fixation: 57.8% of cases show a dip at 2000 Hz 1
  • Middle ear effusion (glue ear): The presence of a Carhart notch predicts glue at myringotomy with 87.4% accuracy (P < 0.001), with only 1.1% false positives 2

The 1000-2000 Hz Downslope Pattern

When you see a steep downslope of >10 dB from 1000 Hz to 2000-3000 Hz, this suggests:

  • Ossicular discontinuity: 75.0% of cases demonstrate this pattern, often with a dip extending to 3000 Hz (56.3% of cases) 1

Distinguishing Specific Pathologies

For Ossicular Fixation (when 2000 Hz dip is present):

Low-frequency pattern matters:

  • Upslope at ≤1000 Hz: Higher probability of malleus or incus fixation
  • Downslope at ≤1000 Hz: Higher probability of stapes fixation (likelihood ratio = 4.9, P < 0.001) 1

For Ossicular Discontinuity (when 1000-3000 Hz downslope is present):

Low-frequency pattern matters:

  • Upslope at ≤1000 Hz: Higher probability of incomplete discontinuity
  • Downslope at ≤1000 Hz: Higher probability of complete discontinuity (likelihood ratio = 6.6, P = 0.018) 1

Clinical Action Required

Any air-conduction threshold >20 dB at 1000 Hz or 2000 Hz warrants referral to an audiologist for comprehensive evaluation 3. The bone conduction pattern provides critical preoperative diagnostic information about the specific middle ear pathology requiring surgical intervention.

Common Pitfall to Avoid

Do not confuse this with the normal acoustic phenomenon at 1000 Hz in air conduction testing, which relates to front-back sound localization and is not pathologic 4. The clinically significant dip occurs in bone conduction thresholds and indicates mechanical middle ear dysfunction requiring treatment.

The bone conduction threshold pattern serves as a valuable preoperative diagnostic tool that can guide surgical planning and predict intraoperative findings with high accuracy 1, 2.

References

2
Research

Could the presence of a Carhart notch predict the presence of glue at myringotomy?

Clinical otolaryngology and allied sciences, 2003

4
Research

Front-back sound level differences for human heads and the 1000-Hz interaural level anomaly.

The Journal of the Acoustical Society of America, 2026

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Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.