PP510 - On the Road: Audiometric Threshold Reliability in a Mobile Research Vehicle

Abstract:
Mobile research vehicles (MRV) can be used in audiological research for a variety of reasons, including in our work to maintain enrollment of a broad participant pool in a longitudinal study examining audiological outcomes of children with otitis media (OM). As part of this work, behavioral audiometry is completed in an MRV. The purpose of this study was to compare audiometric thresholds obtained in the MRV to those obtained in a sound treated booth. Preliminary analyses suggest that air conduction threshold results are within test-retest reliability in the two settings, while bone conduction results are significantly higher in the MRV.

Summary:
The Translational Auditory and Perception Laboratory uses a mobile research vehicle (MRV) to maintain enrollment of an extensive participant pool in a longitudinal study examining audiological outcomes of children with otitis media (OM). MRVs allow researchers to access a broader participant population by removing known barriers to research participation.

The protocol includes the assessment of audiometric thresholds in the MRV. The MRV is not a sound treated booth, and as such, the limitations of audiometric testing in the MRV need to be investigated to determine the reliability of audiometric threshold testing in this setting. The purpose of this study was to compare audiometric thresholds obtained in a standard, sound-treated booth in the laboratory to those obtained in the MRV.

Twenty-seven participants of any hearing status, ages 5 years to 40 years, completed hearing assessments in the sound-treated booth in the laboratory as well as in the MRV. Octave frequencies 250 to 8000 Hz were tested using a mobile audiometer (MAICO MA 42) with circumaural headphones with significant passive attenuation (Radio Ear DD65v2, with a passive attenuation ranging from 15 to 46 dB, average 35 dB) in the MRV and using an audiometer (Masden Astera2) with circumaural headphones (Sennheiser HDA 300) in the laboratory sound booth.  Bone conduction testing at octave frequencies from 250 to 4000 Hz was completed on a subset of participants (N=12). In addition, baseline measurements of ambient sound levels were obtained in both testing locations. Sound level measurements were averaged over 1 minute in both the MRV and in the sound booth using the NIOSH SLM application and calibrated microphone. The average MRV levels in quiet were 42.0 dBA. In the sound booth, average levels in quiet were 29.9 dBA.

Average air-conduction thresholds at all frequencies (250-8000 Hz) were within test-retest reliability standards between the MRV and sound booth, though statistically significant differences were observed at 250 and 4000 Hz, with elevated thresholds in the MRV at these frequencies. Average bone conduction thresholds were significantly elevated in the MRV from 250 through 2000 Hz but were not statistically significantly different at 4000 Hz.

This study establishes the feasibility of completing behavioral audiometric hearing assessment for research purposes in MRVs that have not undergone sound treatment. Air conduction thresholds using circumaural headphones with significant passive attenuation were found to reliably match those obtained in a sound treated booth. However, bone conduction thresholds were not found to be reliable in the MRV, presumably due to the higher ambient noise levels observed.