抄録
Errors and scatters in usual absorption measurement in a reverberation room are mainlycaused by non-diffusion condition and edge effect, which unfortunately differ from room toroom. This paper presents a method termed “PLD/Deep-well” which eliminates theseerror sources and finally yields random incident absorption coefficient, α∞, by two procedure:(1) mounting “Deep-well, ” reflective panel taller than the thickness of the specimen, closely around its perimeter to eliminate the edge effect, and (2) applying “PLD (Power-law decay) approach” which compensates the lack of diffusion including what may be aggravated by procedure (1) through numerical evaluation of the curvature on the space-ensemble average decay process {<S2 (t)>} No, i.e., through direct prediction of total room absorptionfor perfect diffusion. Several α∞ measurements were made to examine the validity of theproposed method, as well as computer simulation to confirm it from the qualitative viewpoint.The results imply the method gives α∞ with high precision and reproducibility, independent of the area, shape and location of the specimen, diffusion condition, and theheight of the well H only if H≥H0+t, where t is the thickness of the specimen and H0 theminimum required height of the well which turned out about 0.8m for usual reverberation room.
