Measuring the real-ear to coupler difference transfer function with an insert earphone and a hearing instrument: are...

Area of Science:

• Audiology
• Acoustics
• Hearing Instrument Technology

Background:

• The real-ear to coupler difference (RECD) is crucial for hearing instrument fitting and verification.
• Accurate RECD measurements ensure proper amplification and patient benefit.
• Variations in sound delivery systems can influence RECD outcomes.

Purpose of the Study:

• To compare RECD measurements obtained with an insert earphone versus two behind-the-ear hearing instruments.
• To assess the reliability and potential discrepancies in RECD measurements across different sound sources.
• To determine if insert earphones can accurately represent hearing instrument performance in RECD testing.

Main Methods:

• RECD was measured in 18 normal-hearing subjects using a probe-tube microphone system.
• Measurements were taken with a conventional ER-3A insert earphone and two hearing instrument models.
• RECD was calculated by subtracting 2-cc coupler (HA1 and HA2) responses from real-ear aided responses.

Main Results:

• The measurement procedures demonstrated high reliability with retest differences under 1 dB.
• Statistically significant differences (p < 0.05) were found between RECDs from insert earphones and hearing instruments.
• The largest RECD differences occurred with the HA2 coupler, reaching up to 11 dB between an insert earphone and a hearing instrument.

Conclusions:

• RECD is influenced by the acoustic impedance of the sound source, coupling system, and coupler.
• Differences in acoustic impedance between insert earphones and hearing instruments can lead to variable RECDs.
• RECD measurements using insert earphones may not always accurately reflect hearing instrument performance compared to coupler measurements.