The Impact of Signal Bandwidth on Auditory Localization: Implications for the Design of Three-Dimensional Audio Displays

A new type of interface, the three-dimensional (3D) audio display, is being developed to enhance cockpit displays in military aircraft. In order to synthesize a sound's location in space, head-related transfer functions are measured for many sound source positions (in space) and incorporated in digital filters, which are then used to synthesize location. However, most military aircraft have communication systems that are band-limited in frequency response, as are most recently designed auditory displays currently used in military applications. The present study investigated the effects of limiting signal bandwidth on sound localization. Results show that broadband signals encompassing frequencies from 0 to (at least) 13 kHz are required in order for listeners to accurately localize signals actually presented from a range of spatial locations. These results have clear implications for the design and implementation of 3D spatial synthesis systems in military aircraft. Communications systems should be capable of carrying broadband signals and acoustic signals used in 3D audio displays should also be broadband in nature.