ASA 124th Meeting New Orleans 1992 October

4aAA7. An experimental investigation of masked-threshold and just-notice-level differences of early reflection in a room.

Toshiyuki Okano

Takayuki Hidaka

Takenaka Tech. Res. Lab., 2-5-14 Minamisuna, Koto-ku, Tokyo 136, Japan

Masked-threshold-level (MTL) and just-notice-level differences (jnld) are two of the most basic and important attributes of early reflection in a room's sound field because they are deeply related with necessary accuracy of sound field simulation and with subjective efficiency of early reflection. MTL and jnld of reflection were measured using a music source signal. Various types of sound fields that were composed of multiple reflections were tested. MTL of a reflection rises when an additional reflection is added because of the increase of masking by the additional reflection. The rise of MTL is larger than the energy summation low, which is basically the same as the addition of simultaneous masking. The rise of MTL influences jnld of reflection. The jnld becomes larger as the reflection level becomes closer to its MTL, and is expressed as a function of L[sub T], which is the reflection level relative to its MTL.