Effect of latency time in high frequencies on sound localization

Tactical military headsets allow hearing protection and communication between soldiers using surround technology. In this paper, we investigate the effect of latency time between low and high frequencies on the ability of a person to correctly identify an external sound source direction with tactical military headsets. The latency time between low and high frequencies results from a digital processing unit. Low frequencies from an external sound source are not processed; therefore, they are received in the ear canal before the digitally processed higher frequencies. Two experiments were conducted using non-individualized Head Related Transfer Function and headphones for trained and untrained volunteers. The experiments were done for two types of sources: human speech and white Gaussian noise, and were performed with latency times of zero, 20msec, and 40msec applied to frequencies below 20Hz. The experimental results show that the errors in sound localization accuracy in both experiments are fewer for signals without latency time, compared to processed signals with latency times between low and high frequencies.