Interactions between hearing aid and patient in the individual fitting situation

Area of Science:

• Audiology
• Acoustics
• Biomedical Engineering

Background:

• Individual anatomical variations in the ear canal and middle ear affect hearing aid performance.
• Standardized measurements using KEMAR (Knowles Electronics Manikin for Acoustic Research) provide a baseline but do not fully account for patient-specific acoustics.

Purpose of the Study:

• To investigate the feasibility of introducing an adjustment factor for hearing aid fitting based on individual ear mould characteristics.
• To quantify the variation in insertion gain across different hearing aids when fitted to the same individual.

Main Methods:

• Testing multiple hearing aids on the same individual with custom ear moulds.
• Comparing the measured insertion gain against KEMAR data to assess deviations.

Main Results:

• Significant variations in insertion gain were observed for identical hearing aids across different individuals and even for the same individual with different hearing aids.
• The extent of variation indicated that a single, universal adjustment factor is not directly applicable.

Conclusions:

• Hearing aid fitting requires consideration of individual acoustic load impedance.
• Predicting hearing aid effectiveness necessitates understanding the device's sensitivity to specific patient ear canal acoustics.