Validity and reliability of integrated pressure level real-ear-to-coupler difference measurements

Abstract

Objectives

(1) To validate the measurement of foam-tip real-ear-to-coupler differences (wRECD) using an integrated pressure level (IPL) method and (2) to compare the reliability of this method to SPL-based measurement of the wRECD.

Design

SPL-based wRECD and the proposed IPL wRECD measurement were completed bilaterally. Test-retest reliability of IPL wRECD was determined with full re-insertion into the ear canal and compared to published SPL wRECD test-retest data.

Study sample

22 adults with normal hearing and middle ear status were recruited.

Results

Differences between SPL-based wRECD and IPL wRECD measurements were within 1.51 dB on average below 5000 Hz. At and above 5000 Hz, IPL wRECD exceeded SPL wRECDs by 6.11 dB on average. The average test-retest difference for IPL wRECD across all assessed frequencies was 0.75 dB with the greatest improvements in reliability found below 750 Hz and above 3000 Hz.

Conclusions

IPL wRECD yielded improved estimates compared to SPL wRECD in high frequencies, where standing-wave interference is present. Independence from standing wave interference resulted in increased wRECD values above 4000 Hz using the IPL measurement paradigm. IPL wRECD is more reliable than SPL wRECD, does not require precise probe-microphone placement, and provides a wider valid wRECD bandwidth than SPL-based measurement.

Keywords:

• Real-ear measurements
• RECD
• assistive technology
• hearing aids
• instrumentation
• middle ear
• tele-audiology/tele-health

Acknowlegements

This work was supported by Ontario Research Fund (RE-08-072). The authors are grateful to Jonathan Vaisberg for sharing raw data from previous studies. The authors are also grateful to Audioscan, a Division of Etymotic Design Incorporated, and Interacoustics A/S for their technical support throughout the study.