Evaluation of an Auditory Localization Training System for Use in Portable Configurations: Variables, Metrics, and Protocol

Hearing protection can mitigate the harmful effects of noise, but for Service Members these devices can also obscure auditory situation awareness cues. Tactical Communication and Protective Systems (TCAPS) can restore critical cues through electronic circuitry with varying effects on localization. Evidenced by past research, sound localization accuracy can improve with training. The investigator hypothesized that training with a broadband stimulus and reducing the number of presentations would result in training transfer. Additionally, training transfer would occur with implementation of more user-engaged training strategies. The purpose of the experiments described in this study was to develop an optimized auditory azimuth-training protocol for use in a field-validated portable training system sensitive to differences among different TCAPS.

A series of indoor experiments aimed to shorten and optimize a pre-existing auditory localization training protocol. Sixty-four normal-hearing participants underwent localization training. The goal of training optimization included the following objectives: 1) evaluate the effects of reducing stimulus presentations; 2) evaluate the effects of training with a broadband stimulus (but testing on untrained military-relevant stimuli); and 3) evaluate performance differences according to training strategies.

Twenty-four (12 trained and 12 untrained) normal-hearing listeners participated in the field-validation experiment. The experiment evaluated localization training transfer from the indoor portable system to live-fire blanks in field. While training conducted on the portable system was predicted to transfer to the field, differences emerged between an in-the-ear and over-the-ear TCAPS. Three of four untrained stimuli showed evidence of training transfer. Shortening the training protocol also resulted in training transfer, but manipulating training strategies did not. A comparison of changes in localization scores from the indoor pretest to the field posttest demonstrated significant differences among listening conditions. Training improved accuracy and response time for the open ear and one of two TCAPS. Posttest differences between the two TCAPS were not statistically significant.

Despite training, localization with TCAPS never matched the open ear. The portable apparatus employed in this study offers a means to evaluate the effects of TCAPS on localization. Equipped with a known effect on localization, TCAPS users can render informed decisions on the benefits or risk associated with certain devices.