DRDC Toronto Research Centre Toronto, Ontario Canada
Advanced hearing protection technologies enhance speech understanding while protecting against injurious noise. This experiment assessed horizontal plane sound localization with three communication devices with integrated hearing protection, that could amplify environmental sounds. Normal-hearing adults localized a brief noise burst with ears unoccluded and fitted with the Nacre QUIETPRO earplug, Peltor PowerCom Plus earmuff, and Sensear SDP earmuff-earplug combination. These were tested in the passive OFF mode and in the active ON mode at three volume settings. The stimulus was presented by an array of eight loudspeakers surrounding the listener. One block of 80 randomized loudspeaker identification trials was presented under each listening condition. Participants responded using a response box with eight buttons in the same configuration as the array. With ears unoccluded, mean scores were above 90 correct. With the devices in the OFF mode, mean scores were less than 50 , mainly due to confusion of front and back. With the devices ON, an improvement of 21 to 33 was realized. Azimuthal percent correct was highest for sound sources located on either side of the midline axis in front, decreasing front to back, reflecting the placement of the external microphones on the devices. Increasing the volume had no effect.