Evaluation and improvement of the diffusivity in a reverberation chamber for precise estimation of absorption coefficients

The current ISO standard for measuring the absorption coefficient in reverberation chambers (ISO 354) has an incredibly poor inter-chamber reproducibility, e.g., the difference in the absorption of an identical sample can be as large as 0.4 between two certified chambers. The main reason for the huge deviation is that the degree of diffusion (diffusivity) in the test chamber varies a lot from one to another in a diversely different manner. However, there has been no diffusivity indicators accepted by the acoustic society worldwide.

Recently Melanie’s master thesis at DTU suggested a few promising indicators, thus the goal of this innovation project is to apply these indicators to other chambers and to suggest methods to improve the diffusivity, and correspondingly the reproducibility in the measured sound absorption. Imprecise absorption data are huge problems for both absorber manufacturers and users of the absorption data.

This project will end up with the following four deliveries.

  1. main factors that influence the absorption measurements.
  2. the diffusivity indicators in reverberation chambers.
  3. ways to improve the diffusivity when it is insufficient,
  4. precise absorption database for computer simulations.

This project is planned to continue as a PhD project at DTU.

Project participants:
Ecophon
Odeon
Peutz
Cowi

For more information, contact Project Leader:
Associate Professor Cheol-Ho Jeong
Technical University of Denmark, Electrical Engineering
chj@elektro.dtu.dk