Development and Calibration of a New Automated Method to Measure Air Conduction Auditory Thresholds Using an Active Earplug

A new automated method termed as 'New Early Warning Test (NEWT)' has been designed to provide automatic auditory threshold monitoring in individuals exposed to high noise levels. The NEWT method is incorporated inside an active communication earplug called Quietpro (R), which has high attenuation characteristics for background noise. The NEWT measures auditory thresholds using a two-peep pure tone stimulus. The aim of the present study was to establish the calibration values required for the NEWT method by comparing the deviations in the thresholds obtained in the NEWT against standard pure tone audiometry (PTA). Sixteen subjects (twenty-eight ears) with normal hearing participated in this study. Auditory thresholds were measured using the NEWT and PTA for frequencies of 1, 3, 4 and 6 kHz. It was observed that there was no significant difference in inter-subject variability. Because this inter-subject variability also included intra-subject variability, results suggested that the NEWT method had at least not any higher intra-subject variability than the PTA. Results of the present study will be used to calibrate the NEWT method, which helps in regular monitoring of hearing status in individuals exposed to noise. These results might have important implications to further evaluate the NEWT method on various groups of population having different degrees of hearing loss.