When listening to a 5.1 movie soundtrack through headphones, the six channels are normally down-mixed to two-channel stereo, and thus losing the spatial sensations associated with surround sound.

The approach in this project was to down-mix the signals into two channels, while additionally including the acoustical filtering that would have occurred, if reproduced through six loudspeakers. The final system runs in real time based on suitable parameters found through listening tests.

Binaural Reproduction over Headphones Animation
BRIR Surround

The acoustical fillters have been obtained by measuring binaural room impulse responses (BRIRs) in a dedicated multi-channel listening room. The binaural recording head VALDEMAR was used. The BRIRs were measured in specific positions matching the standard 5.1 surround sound setup.

DVD movies were used as source material from which six discrete audio signals were extracted. These signals were convolved with the BRIRs, equalized for measurement and reproduction chain, and down-mixed into two headphone channels.
Listening Test

A listening experiment was conducted with 20 subjects, evaluating different parameters in the binaural synthesis (surround sound in headphones) implementation.

The implemented system was verified by comparing it to a corresponding binaural recording. It was concluded that the BRIRs can be relatively short without deterioration in sound quality.

Binaural Synthesis Surround Downmix GUI

The binaural synthesis MATLAB program is capable of generating a binaural downmix with various parameters.


PDF logo Merchel, S., Biedermann, I., Joergensen, O. O., Matejka, M., Poncet, D. J., Soerensen, M. O. (2004). Reproduction of Surround Sound in Headphones, Project Report, Aalborg University

 

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Binaural synthesis GUI* (23 MB)

All files in the folder are needed for the program to run. Program is started by running 'BinauralSynthesis.m' in MATLAB.
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Inverse filter creation (1 MB)

All files in the folder are needed for the program to run. Program is started by running 'calculateinversefilters.m' in MATLAB. The program is configured by editing the file.
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Measurement data* (24 MB)

The subfolders contain all .tim files obtained with WinMLS & MLSSA. The measurements include BRIRs, headphone transfer functions, HRTFs, loudspeaker measurements, reverberation time measurements, and wave-files with level and noise floor measurements.

*Note that the method to measure head related transfer functions (HRTFs) in the blocked ear canal is patented.