External ear resonance in patients with tympanic membrane perforations

Area of Science:

• Audiology
• Otoacoustic Emissions
• Bioacoustics

Background:

• The tympanic membrane (eardrum) plays a crucial role in sound transmission.
• External ear resonance influences sound perception and hearing aid effectiveness.
• Understanding how perforations affect ear canal acoustics is vital for audiological rehabilitation.

Purpose of the Study:

• To investigate the impact of tympanic membrane perforations on external ear resonance.
• To compare acoustic resonance characteristics between perforated and normal ears.
• To identify implications for hearing aid fitting in patients with eardrum perforations.

Main Methods:

• External ear resonance was measured using a probe-tube microphone system.
• 14 patients with medium to large unilateral tympanic membrane perforations were studied.
• Contralateral normal ears served as controls for comparison.

Main Results:

• No significant differences were found in peak frequency, amplitude, or sharpness between perforated and normal ears.
• Intersubject variability of resonant frequency was notably higher in the perforated ear group.
• Resonance curves in perforated ears often displayed multiple peaks and reduced gain in the lower frequency range (0.3-2 kHz).

Conclusions:

• While primary resonance parameters remain similar, tympanic membrane perforations alter external ear acoustic behavior.
• Increased intersubject variability and modified resonance curves in perforated ears necessitate adjustments in hearing aid fitting protocols.
• Consideration of these acoustic anomalies is essential for optimizing audiological outcomes in patients with eardrum perforations.