Takenaka Res. and Development Lab., 2-5-14 Minamisuna, Koto-Ku, Tokyo, 136 Japan
Necessary accuracy for early reflection levels was investigated in order to derive criteria to verify the accuracy of a sound field simulator. Early reflections are the most important in controlling the subjective impression of a room's sound field. The accuracy of the sound field simulator depends primarily on the accuracy of early reflections. The just-noticeable level difference (jnld) of early reflections defines the maximum of allowable level difference between real and simulated reflections. Also, the masked threshold level (MTL) of early reflections defines the level of the smallest reflections which a simulator should generate. However, jnld and MTL of early reflections depend on the sound field's configuration. It is desirable that criteria are independent of the configuration of the sound field. The jnld and MTL were measured for lateral and ceiling reflections in various types of rooms with simulated sound fields. Measured jnlds and MTLs were converted into the difference in objective parameters (LE, IACCE, C80, etc.), which correspond to subjective impressions caused by early reflections. Criteria for necessary accuracy were pursued in the domain of rooms with objective acoustic parameters.