A patient is prescribed a behind-the-ear (BTE) hearing aid. The most common cause of acoustic feedback (whistling) from the hearing aid is:
- A Excessive gain setting
- B Poor earmold fit allowing amplified sound to leak from the ear canal back to the microphone ✓
- C Battery failure
- D High-frequency SNHL requiring low-frequency amplification
Correct answer: B. Poor earmold fit allowing amplified sound to leak from the ear canal back to the microphone
Explanation
Acoustic feedback (the characteristic whistle) occurs when amplified sound escaping around a poorly fitting earmold re-enters the hearing aid microphone and is re-amplified in a positive feedback loop. This is the most common cause of feedback and is addressed by recasting/refitting the earmold or using digital feedback suppression algorithms. Excessive gain is a contributing factor but the root cause is earmold leak. Battery failure causes intermittent sound loss, not feedback.
Reference: Dhingra Diseases of Ear, Nose and Throat, 7th ed.
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Written and medically reviewed by the StethoPrep medical team.