Predicting reverberation times in a simulated classroom

Abstract

By varying the sound-absorption treatments in a simulated classroom, experimental results were compared with analytical and computer predictions of reverberation time. Analytical predictions were made with different absorption exponents, which are the result of different weighting procedures involving room surface areas and the sound-absorption coefficients. Sound scattering was found to influence measured reverberation times. With the amount of sound scattering provided, more accurate analytical predictions were obtained with absorption exponents that give reverberation times longer than those obtained with the Sabine absorption exponent, which consistently underpredicted reverberation times. However, none of the absorption exponents could be singled out as more adequate because of similar average accuracy. Computer predictions of reverberation time were accomplished with two commercially available ray-based programs, RAYNOISE 3.0 and ODEON 2.6, with specular and calibrated diffuse reflection procedures. Neither type of procedure, in either program, was more accurate than the best analytical predictions. With RAYNOISE, neither the specular nor the calibrated diffuse reflection procedure could be singled out as more adequate. For ODEON, the calibrated diffuse reflection procedure gave consistently more accurate predictions than its specular reflection procedure, with the best accuracy of the computer predictions.

A Revised Sound Energy Theory Based on a New Formula for the Reverberation Radius in Rooms with Non-Diffuse Sound Field

“…However, one of the limits of the theories alternative to the classic diffuse sound field is that they often underestimate the reverberation time (Mehta, Mulholland, 1976;Bistafa, Bradley, 2000;Ducourneau, Planeau, 2003). For this reason, the Sabine's formula and the diffused sound theory are still widely used.…”

Experimental and numerical studies on reverberation characteristics in a rectangular room with unevenly distributed absorbers

“…However, none of these formulae have been able to consistently predict the reverberation time with sufficient accuracy [7], because these formulae have the same energy-based form as Sabine's formula. The only difference between these formulae and Sabine's formula is that the absorption exponents are used in these formulae, rather than the average absorption coefficient, to express the characteristics of various types of rooms.…”

Projektowanie Akustyczne Wnętrz W Świetle Nowych Wymagań

“…Zatem nie jest to problematyka pomijalna podczas projektowania takich pomieszczeń. Podobne efekty zauważono w pracy [11], w której autorzy zmieniali w klasach szkolnych powierzchnie pochłaniające i analizowali wyniki między innymi w programie ODEON.…”