Evaluation of a Numerical Method for Identifying Surface Acoustic Impedances in a Reverberant Room
Invited paper
KU Luven ESAT - STADIUS
Monday 1 june, 2015, 15:20 - 15:40
0.9 Athens (118)
Abstract:
Wave-based room acoustic simulations are becoming more popular as the available compute power
continues to increase. The definition of boundary conditions and acoustic impedance is of fundamental
importance for these simulations to succeed in representing a realistic acoustical space. Acoustic
impedance databases exist in terms of absorption coefficients, which are usually measured in reverberation
chambers. In this type of measurements, the sound field is assumed to be diffuse, a condition which is not
met in most rooms. In particular at low frequencies, where wave-based simulations are possible, a
different approach is sought for as an alternative to acoustic impedance measurements.
This paper focuses on a recently proposed method for measuring acoustic impedance. This method is
based on the use of a numerical room model, and does not require the assumption of a diffuse field.
Assuming that the geometry of the room is known, a Finite Difference Time Domain (FDTD) simulation is
matched with measured data by solving an optimization problem. The set-up of such a measurement
method consists only of a set of microphones and a loudspeaker. This can be applied in every room,
removing the need for expensive facilities such as reverberation chambers. The solution of the
optimization problem leads to the sought parameters of the acoustic impedance.
The results obtained so far on the development of this method have been only validated through
simulations and the focus has mainly been on the optimization algorithm. In this paper instead, the focus
will be on the problems that may occur when applying this method using real room measurements.
Solutions and modifications will be proposed to make it possible to apply this method in a realistic
environment.