The Chalmers Auralization Toolbox is a collection of MATLAB scripts that auralize sampled sound fields. The sound field quantity that is sampled can be either the sound pressure or the combination of sound pressure and particle velocity (or equivalently the sound pressure gradient). The primary purpose is auralization of data simulated with methods like FDTD, FEM, BEM, and the like.
Binaural audio examples that were created with the toolbox are available here.
The figure below illustrates the types of sampling grids that can be processed (volumetric, spherical surfaces, and cubical surfaces).
The sampled data can be converted to either an ambisonic representation, which can then be rendered both binaurally and using loudspeaker arrays. The conventions that we use (i.e. N3D and ACN) are compatible with software tools like SPARTA and the IEM Plugin Suite. Or, the sampled data can be rendered binaurally without an intermediate format (direct rendering).
You'll need to download the employed HRIRs of a Neumann KU 100 manikin from here and store them in the subfolder hrtfs (The MATLAB script is going to do that automatically for you, both the downloading and creating that folder.) as well as the SOFA MATLAB API from here.
The toolbox was originally presented in
Jens Ahrens, "A Software Tool for Auralization of Simulated Sound Fields," Auditorium Acoustics, Athens, Greece, 2023 [ pdf ]
The work is on-going, so please revisit this repository regularly for updates. Note that some of the implementations are in an experimental state. Make sure that you get in touch with us at [email protected] if things behave differently than you were expecting.
In the folder resources, we provide example data for a reverberant room with a reverb decay time of around 1 s ("big hall") as well as a much dryer living-room type room ("living room"). You will find information on the input data format in that folder. The data are based on measurements of the responses of the two rooms. We will explain shortly how we processed the data to obtain both ground truth binaural signals as well as the sound pressure at arbitrary points in space.
The example grids comprise approx. 300 sampling points. This produces good results, but the auralization is not perfectly transparent meaning that there are cases in which the auralization can be distinguished from the ground truth (refer to the audio examples above). Increasing the number of sampling point will eventually overcome the deviations. Yet, we are working on updates on the methods that can potentially yield perceptually transparent auralization with the present or even lower number of sampling points.
The direct rendering is rather slow currently (in the order of minutes). This is because this method requires the sound pressure due to a large number of plane waves to be computed on the sampling grid. For the time being, we chose to compute this via a spherical harmonic representation, which is computationally expensive. We will replace this in the future with a more efficient computation, which will reduce the computation time to seconds.
We will provide examples that demonstrate how data from the most common room acoustic simulation softwares can be auralized with our toolbox.
Auralization of volumetrically sampled sound fields via ambisonics:
B. Støfringsdal and U.P. Svensson, 'Conversion of Discretely Sampled Sound Field Data to Aualization Formats,' J. Audio. Eng. Soc. 54(5), pp. 380-400 (May 2006)
J. Sheaffer, M. van Walstijn, B. Rafaely, and K. Kowalczyk, 'Binaural Reproduction of Finite Difference Simulations Using Spherical Array Processing', IEEE/ACM TASLP 23(12), pp. 2125-2135 (Dec. 2015)
Auralization of sound fields sampled on a spherical surface via ambisonics:
I. Balmages and B. Rafaely, 'Open-sphere designs for spherical microphone arrays,' IEEE TASLP, vol. 15, no. 2, pp. 727– 732 (2007)
Direct auralization of volumetrically sampled sound fields:
M. A. Poletti and U. P. Svensson, 'Beamforming Synthesis of Binaural Responses From Computer Simulations of Acoustic Spaces,' J. Acoust. Soc. Am. 124, pp. 301–315 (2008)
As to our awareness, direct auralization of sound fields sampled along surfaces as well as auralization of sound fields sampled on a cubical surface via ambisonics has not been presented before. Here, you'll find documentation on all ambisonics-based methods that the Chalmers Auralization Toolbox comprises. A detailed documentation of the direct methods will be provided shortly.
The content of this repository is licensed under the terms of the MIT license. Please consult the file LICENSE for more information about this license.