@article {Rindel:2015:1610-1928:1211,
title = "Modal Energy Analysis of Nearly Rectangular Rooms at Low Frequencies",
journal = "Acta Acustica united with Acustica",
parent_itemid = "infobike://dav/aaua",
publishercode ="dav",
year = "2015",
volume = "101",
number = "6",
publication date ="2015-11-01T00:00:00",
pages = "1211-1221",
itemtype = "ARTICLE",
issn = "1610-1928",
url = "https://www.ingentaconnect.com/content/dav/aaua/2015/00000101/00000006/art00017",
doi = "doi:10.3813/AAA.918914",
author = "Rindel, Jens Holger",
abstract = "This paper describes a method where the normal modes of a rectangular room are analysed as independent resonant systems with internal losses derived from the absorption properties of the room surfaces. Thus the resonance frequency, the bandwidth, and the decay rate of each normal mode
can be calculated. A new method using a representative wave has been applied to calculate the decay rate of a normal mode. By adding the frequency responses of all normal modes up to a sufficiently high order the global frequency response below 200 Hz is found. The decay curve within a frequency
band can be calculated by adding together the individual decay curves of the relevant modes. Typically the axial modes have longer reverberation times than tangential and oblique modes, and thus the total decay curve will not be a perfectly straight line. The effect of angled walls or scattering
treatment of surfaces is modelled in terms of modal energy analysis, the most important result being that sound energy is transferred from the powerful axial modes to other modes with less energy, and thus leading to a shorter reverberation time. A new theoretical model for energy losses of
axial modes due the scattering or angled walls is presented. The presented model using modal energy analysis is suggested as a tool for the analysis and design of small music practice rooms and recording studios.",
}