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Effects of probe insertion depth on real ear measurements
D D Dirks1, J B Ahlstrom, L S Eisenberg
1Division of Head and Neck Surgery, UCLA School of Medicine 90024.
Summary
Probe insertion depth significantly impacts real ear measurements. An acoustic method yielded higher sound pressure levels than constant depth or earmold +5 mm methods, especially in longer ear canals and at high frequencies.
Area of Science:
- Audiology
- Acoustics
- Hearing Science
Background:
- Accurate real ear measurements are crucial for hearing aid fitting.
- Probe microphone systems are standard for real ear verification.
- Probe insertion depth can influence measurement accuracy.
Purpose of the Study:
- To summarize the effect of probe insertion depth on real ear measurements.
- To compare three probe positioning methods for real ear sound pressure level (SPL) measurements.
Main Methods:
- Compared acoustic, constant depth (25 mm), and earmold +5 mm probe insertion methods.
- Measured real ear SPL at 32 frequencies in 17 subjects' unoccluded ears.
- Utilized the quarter-wave antiresonance property for acoustic method localization.
Main Results:
- The acoustic method resulted in significantly higher SPLs compared to the other two methods.
- This difference was most pronounced in subjects with ear canals longer than 25 mm and at high frequencies (4.0–6.3 kHz).
- For shorter or average ear canals, all three methods yielded comparable results.
Conclusions:
- Probe insertion depth is a critical factor in real ear measurements.
- The acoustic method may provide more accurate SPL readings in specific ear canal lengths and frequency ranges.
- Careful consideration of probe positioning is necessary for precise hearing aid verification.