Smartphone-based hearing tests for a Virtual Hearing Clinic: Influence of ambient noise on the absolute threshold and loudness scaling at home

Authors: Chen Xu1*, Lena Schell-Majoor1, Birger Kollmeier1

1University of Oldenburg

Background Ambient noise tends to be one of the critical factors that might influence the accuracy of mobile hearing tests at home, e.g., within a Virtual Hearing Clinic (VHC). Active ambient noise monitoring during out-of-booth measurements can be used to control the overall test environment and to indicate whether the environment is suitable for hearing tests.

Method Two audiometric tests, i.e., air-conduction pure-tone audiometry and categorical loudness scaling (CLS) were conducted remotely at 0.25, 1, and 4 kHz in N = 15 normal hearing subjects while the environmental noise was measured using an integrated microphone and a dosimeter app on a smartphone. Furthermore, CLS got reinforced by placing more trials near the threshold level to handle the fluctuating ambient noise. Thresholds estimated from CLS were compared to pure-tone thresholds to evaluate the performance of the reinforced CLS. The consistency was examined by comparing the at-home measurement to the in-booth measurement while the test-retest reliability was evaluated by comparing two runs outside a booth.

Results The median noise level (i.e., 36.0 dB A) was in general beneath the maximum permissible ambient noise level (MPANLs, ANSI S3.1–1999 (R2018)). Smartphone-based hearing tests exhibited good consistency while moderate-to-good reliability. The modified CLS outperformed the baseline method by yielding a stronger cross correlation and a smaller root-mean-square deviation from pure-tone thresholds in behavioral experiments.

Conclusion Overall, an environmental noise control enables the plausible, consistent, and reliable performance of the two audiometric tests in a home environment. This makes the absence of a booth tolerable for a smartphone-based virtual hearing clinic.