The Effect of Direct-to-Reverberant Energy Ratio on Front-Back Confusion in Binaural Reproduction

The effect of direct-to-reverberant ratio (DRR) on front-back confusion in binaural reproduction was investigated. Binaural room impulse responses (BRIRs) of loudspeakers at 0° and 180° azimuths from the listening position were captured in an ITU-R BS.1116-3-comp1iant listening room (RT=0.25s) using a KU100 dummy head placed 2m away from each loudspeaker. The DRRs of the original BRIRs were manipulated by varying the levels of the reverberant parts (beyond 2. 5ms after the direct sound) of the signals, producing BRIRs with DRRs ranging from -12 dB to 12 dB with 4 dB intervals for each source position, as well as a pseudo-anechoic HRIR condition. Five subjects participated in the initial listening test. Each front or back stimulus with a different DRR was presented 20 times in a random order and the subject's task was to respond either Front or Back. From psychometric functions derived from the data collected, a consistent pattern was observed from all subjects in that a lower DRR (more reverberant) tended to cause a higher rate of front-to-back confusion, whereas a higher DRR produced a higher rate of back-to-front confusion. The DRR thresholds of discrimination were different between the front and rear located sources, and the region between the two thresholds is proposed as a transition region where an extreme chance of confusion can be avoided for both source positions.