Evidence-based occupational hearing screening II: validation of a screening methodology using measures of functional hearing ability

Abstract

Objective: Validate use of the Extended Speech Intelligibility Index (ESII) for prediction of speech intelligibility in non-stationary real-world noise environments. Define a means of using these predictions for objective occupational hearing screening for hearing-critical public safety and law enforcement jobs. Design: Analyses of predicted and measured speech intelligibility in recordings of real-world noise environments were performed in two studies using speech recognition thresholds (SRTs) and intelligibility measures. ESII analyses of the recordings were used to predict intelligibility. Noise recordings were made in prison environments and at US Army facilities for training ground and airborne forces. Speech materials included full bandwidth sentences and bandpass filtered sentences that simulated radio transmissions. Study sample: A total of 22 adults with normal hearing (NH) and 15 with mild–moderate hearing impairment (HI) participated in the two studies. Results: Average intelligibility predictions for individual NH and HI subjects were accurate in both studies (r² ≥ 0.94). Pooled predictions were slightly less accurate (0.78 ≤ r² ≤ 0.92). Conclusions: An individual’s SRT and audiogram can accurately predict the likelihood of effective speech communication in noise environments with known ESII characteristics, where essential hearing-critical tasks are performed. These predictions provide an objective means of occupational hearing screening.

Key Words:

• Hearing-critical job tasks
• likelihood of effective speech communication
• Speech Intelligibility Index
• Extended Speech Intelligibility Index
• real-world noise environments

Acknowledgements

The authors acknowledge Lindsay Allen for her support of the field work that produced recordings of the real-world noise environments in US Army training facilities. These recordings were used in Study 2. The authors also wish to acknowledge the contributions of Robert Chambers who designed and implemented the software used in Study 2, as well as Yang-soo Yoon who tested subjects and processed some of the data in Study 2.

Declaration of interest

Two of the co-authors, CL and SDS, have served as experts in legal proceedings that involved occupational hearing screening. No other potential conflicts of interest are to be reported. Funding for the POST study was from the California Peace Officers Standards and Training Commission. Funding for the DFO study was from the Canadian Coastguard and Department of Fisheries and Oceans, Canada. Funding for the CSA study was from the California Corrections Standards Authority. Funding for the OC study was from the Ontario Ministry of Community Safety and Correctional Services, Canada. Funding for the FBI study was from the US Federal Bureau of Investigation.

The authors have no conflicts of interest to report. Study 1 was supported in part by SBIR grant 1R43DC010962-01 from the National Institutes of Health awarded to Compreval, Inc., and subcontracted to the House Ear Institute, which developed the software tools and test materials used in testing the subjects. Study 2 was supported in part by SBIR grant W81XWH-09-C-0048 from the US Army Medical Research and Material Command awarded to Creare, Inc., and subcontracted to the House Ear Institute. Software tools and test materials for Study 2 were developed by Creare, Inc. Institutional Review Board approval of the informed consent forms and the test protocols for both studies were obtained by the House Ear Institute. All subject testing was done at the House Ear Institute.

Supplementary material available online