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Prediction of Reverberant Properties of Enclosures via a Method Employing a Modal Representation of the Room Impulse Response

Meissner M.

Archives of Acoustics

2016

Vol. 41, No. 1

27--41

A theoretical method has been presented to describe sound decay in enclosures and simulate the room impulse response (RIR) employed for prediction of the indoor reverberation characteristics. The method was based on a solution of wave equation with the form of a series whose time-decaying components represent responses of acoustic modes to an impulse sound source. For small sound absorption on room walls this solution was found by means of the method of variation of parameters. A decay function was computed via the time-reverse integration of the squared RIR. Computer simulations carried out for a rectangular enclosure have proved that the RIR function reproduces the structure of a sound field in the initial stage of sound decay sufficiently well. They have also shown that band-limitedness of the RIR has evident influence on the shape of the decay function and predicted decay times.

Damped forced vibrations of an elastically connected double-membrane system

Oniszczuk Z.

Vibrations in Physical Systems

2008

Vol. 23

295--302

The purpose of the present paper is to consider theoretically damped forced transverse vibrations of an elastically connected rectangular double-membrane system. The system is treated as two viscoelastic membranes joined by a Kelvin-Voigt viscoelastic layer. Applying the modal expansion method, exact analytical solutions of damped forced responses for a simplified model of this system subjected to arbitrarily distributed transverse continuous loads are determined in the case of arbitrary magnitude of linear viscous damping. Nine possible different solutions obtained are described by the combinations of time functions expressing the damped motions for undercritical, critical and overcritical damping cases, according to the mutual relations between physical parameters of the system.