Validity and reliability of in-situ air conduction thresholds measured through hearing aids coupled to closed and open instant-fit tips

Abstract

Abstract

Audiometric measurements through a hearing aid (‘in-situ’) may facilitate provision of hearing services where these are limited. This study investigated the validity and reliability of in-situ air conduction hearing thresholds measured with closed and open domes relative to thresholds measured with insert earphones, and explored sources of variability in the measures. Twenty-four adults with sensorineural hearing impairment attended two sessions in which thresholds and real-ear-to-dial-difference (REDD) values were measured. Without correction, significantly higher low-frequency thresholds in dB HL were measured in-situ than with insert earphones. Differences were due predominantly to differences in ear canal SPL, as measured with the REDD, which were attributed to leaking low-frequency energy. Test-retest data yielded higher variability with the closed dome coupling due to inconsistent seals achieved with this tip. For all three conditions, inter-participant variability in the REDD values was greater than intra-participant variability. Overall, in-situ audiometry is as valid and reliable as conventional audiometry provided appropriate REDD corrections are made and ambient sound in the test environment is controlled.

Sumario

Las mediciones audiométricas a través de un auxiliar auditivo (‘in-situ’) pueden facilitar la prestación de servicios auditivos donde éstos son limitados. Este estudio investigó la validez y confiabilidad de los umbrales auditivos por conducción aérea in-situ, medidos con domos abiertos y cerrados, en relación a umbrales medidos con auriculares de inserción, y exploró las fuentes de variabilidad en la medición. Veinticuatro adultos con hipoacusia sensorineural asistieron a dos sesiones donde se midieron los valores de los umbrales y de la diferencia de oído real a marcación (REDD). Sin corrección, se midieron umbrales en dB HL para las bajas frecuencias significativamente más altos in-situ que con los auriculares de inserción. Las diferencias se debieron predominantemente a diferencias en la SPL del canal auditivo, conforme se midieron con el REDD, y se atribuyeron a fuga de energía en las bajas frecuencias. Los datos de test-retest rindieron una mayor variabilidad con el acoplamiento de domos cerrados, debido al sello inconsistente que se obtuvo con esta punta. Para las tres condiciones, la variabilidad entre los participantes en los valores REDD, fue mayor que la variabilidad intra-participantes. Globalmente, la audiometría in-situ es tan válida y confiable como la audiometría convencional, en la medida que se realicen correcciones REDD apropiadas y que haya control de sonido en el ambiente de evaluación.

Key Words:

• In-situ audiometry
• Test-retest reliability
• Open fitting
• Insert earphones

Acknowledgements

This study was partly funded by Siemens, however, the data analyses and interpretations presented in this paper are solely that of NAL. The authors would like to thank our colleagues Jorge Mejia for developing the Matlab GUIs and for assistance with calibration and troubleshooting, and Margot McLelland for performing the insertion depth measurements on KEMAR. We would also like to thank Matthias Latzel and Matthias Mueller-Wehlau from Siemens Audiologische Technik (SAT) for co-ordinating the project at SAT and for assistance with trouble-shooting the distortion in the in-situ stimuli, respectively.

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.