An experimental study of loudness evaluation of early reflection

The strength of a steady sound field in a hall depends on the direct sound leveland the level of reflections from all boundaries. But for speech and music having impulsivecharacteristics, only the direct sound and the early reflections are effective to the perceivedloudness to the listener according to the integrating ability of the ear. Therefore, a series ofsubjective comparison tests are carried out in an anechoic room, using recorded speech astesting material, and thus conducted to investigate the contribution of short delayed echoes(early reflections) to the loudness evalution. Sound fields consisting of primary sound anddelayed echoes, single or multiple, are produced by electroacoustic means. Results showthat the perceived loudness of the sound field is a function of the echo energy, angle of echoincidence and its temporal distribution. The law of the addition of energy to the echoes witha short delay is not applicable to multiple echoes as well as to a single echo after an intervalexceeding 30-50ms. In certain cases, they are much less than that can be expectedaccording to the said law.