Study On Threshold Of Early Reflection

Early reflections play an important role in auditory perception.However,due to the limited auditory resolution of human and the masking effect of the direct and later reflections,many early reflections cannot be perceived and there are auditory thresholds.The auditory thresholds of early reflections include audible thresholds and spatial thresholds(minimum audible angles).In this paper,a simplified model of single-direct and single-reflection was used to measure these two thresholds through psychoacoustic experiments,and an auditory model was used for analysis.Firstly,audible threshold of early reflection was measured using the three-down-one-up method.The response mode was Three-interval,Three-alternative Forced-choice(3I 3AFC).The experimental results show that:(1)In the selected delay range,the threshold decreases with the increase of the delay;(2)When the early reflection sound and the direct sound are incident from the same direction,the masking effect is the strongest.If the early reflection deviates from the direct sound,the threshold value decreases.Then,the spatial threshold of early reflections was measured.The experimental results show that the delay has no significant effect on the results;and the impact of the incident angle on the results is significant.The degree of attenuation of early reflections relative to direct sound has certain influence on the spatial threshold.In this paper,two attenuation levels were set,with no attenuation and attenuation of 4 dB,respectively,and there is a significant difference between the spatial threshold with attenuation level and the attenuation-free level for some incident angle and delay combinations.Finally,a loudness calculation model was used to analyze the loudness of the above two experiments.In the loudness analysis of the audible threshold,results show that the loudness difference between the target signal and the reference signal increases with the decreasing of the attenuation of the early reflection with respect to the direct sound;While,in the loudness analysis of the spatial threshold,results show that the loudness difference between the target signal and the reference signal increase with the increasing of the deviated angle of the early reflection.The work in this paper helps to further understand the auditory characteristics of earlyreflections,and also provides a basis for simplifying the binaural room impulse response BRIR and suppressing the early reflections in room acoustics design.