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Brännmark, Lars-Johan
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Publications (10 of 15) Show all publications
Brännmark, L.-J. & Sternad, M. (2015). Controlling the impulse responses and the spatial variability in digital loudspeaker-room correction. In: : . Paper presented at 2015 International Symposium on ELectroAcoustic Technologies (ISEAT), Shenzhen, Kina, november. .
Open this publication in new window or tab >>Controlling the impulse responses and the spatial variability in digital loudspeaker-room correction
2015 (English)Conference paper, Published paper (Refereed)
National Category
Engineering and Technology
Research subject
Electrical Engineering with specialization in Signal Processing
Identifiers
urn:nbn:se:uu:diva-267314 (URN)
Conference
2015 International Symposium on ELectroAcoustic Technologies (ISEAT), Shenzhen, Kina, november
Available from: 2015-11-20 Created: 2015-11-20 Last updated: 2015-11-20
Brännmark, L.-J. & Ahlén, A. (2015). Multichannel Room Correction with Focus Control. Journal of The Audio Engineering Society, 63(1-2), 21-30.
Open this publication in new window or tab >>Multichannel Room Correction with Focus Control
2015 (English)In: Journal of The Audio Engineering Society, ISSN 0004-7554, ISSN 1549-4950, Vol. 63, no 1-2, 21-30 p.Article in journal (Refereed) Published
Abstract [en]

Digital equalization of audio systems is mostly performed on a channel-by-channel basis, i.e., loudspeakers are equalized separately and independently of each other. In reverberant rooms the spatial variability of the loudspeaker room transfer function puts a limit on what can be achieved with such single-channel approaches, and considerably more far-reaching results can be obtained with multichannel methods. In this paper we present a multichannel equalizer design method where the loudspeaker to be equalized is assisted by several support loudspeakers that act in combination to improve the response of the main loudspeaker while suppressing the reverberation of the listening room. However, since a full dereverberation may not always be desirable, we shall here study the proposed method from the perspective of how to control the amount of room correction for a given number of contributing support loudspeakers. The amount of correction is controlled by a scalar parameter that we interpret as a "focus control," enabling the user to slide seamlessly between a single-channel equalizer and a full multichannel inversion of the room.

National Category
Other Engineering and Technologies
Identifiers
urn:nbn:se:uu:diva-248653 (URN)000349743200003 ()
Note

Print version: ISSN 1549-4950

Available from: 2015-04-12 Created: 2015-04-06 Last updated: 2017-12-04Bibliographically approved
Barkefors, A., Sternad, M. & Brännmark, L.-J. (2014). Design and Analysis of Linear Quadratic Gaussian Feedforward Controllers for Active Noise Control. IEEE Transactions on Audio, Speech, and Language Processing, 22(12), 1777-1791.
Open this publication in new window or tab >>Design and Analysis of Linear Quadratic Gaussian Feedforward Controllers for Active Noise Control
2014 (English)In: IEEE Transactions on Audio, Speech, and Language Processing, ISSN 1558-7916, E-ISSN 1558-7924, Vol. 22, no 12, 1777-1791 p.Article in journal (Refereed) Published
Abstract [en]

A method for sound field control applied to active noise control is presented and evaluated. The method uses Linear Quadratic Gaussian (LQG) feedforward control to find a Minimal Mean Square Error (MMSE)-optimal linear sound field controller under a causality constraint. It is obtained by solving a polynomial matrix spectral factorization and a linear (Diophantine) polynomial matrix equation. An important component in the design is the control signal penalty term of the criterion. Its use and influence is here discussed and evaluated using measured room impulse responses. The results indicate that the use of a relatively simple, frequency-weighted penalty on individual control signals provides most of the benefits obtainable by the considered more advanced alternative. We also introduce and illustrate several tools for performance analysis. An analytical expression for the attainable performance clearly reveals the performance loss generated by having to use a causal controller instead of the ideal noncausal controller. This loss is largest at low frequencies. Furthermore, we introduce a measure of the reproducibility of the target noise sound field with given control loudspeaker setups and room transfer functions. It describes how well a controller that uses an input subspace of dimension equal to the effective rank of the system is able to reproduce a target sound field. This performance measure can e.g. be used to support the selection of good combinations of placements of control loudspeakers.

National Category
Control Engineering
Identifiers
urn:nbn:se:uu:diva-223813 (URN)10.1109/TASLP.2014.2349856 (DOI)000341627500008 ()
Funder
Swedish Research Council, 2009-5527
Available from: 2014-04-27 Created: 2014-04-27 Last updated: 2017-12-05Bibliographically approved
Brännmark, L.-J., Bahne, A. & Ahlén, A. (2013). Compensation of Loudspeaker-Room Responses in a Robust MIMO Control Framework. IEEE Transactions on Audio, Speech, and Language Processing, 21(6), 1201-1216.
Open this publication in new window or tab >>Compensation of Loudspeaker-Room Responses in a Robust MIMO Control Framework
2013 (English)In: IEEE Transactions on Audio, Speech, and Language Processing, ISSN 1558-7916, E-ISSN 1558-7924, Vol. 21, no 6, 1201-1216 p.Article in journal (Refereed) Published
Abstract [en]

A new multichannel approach to robust broadband loudspeaker-room equalization is presented. Traditionally, the equalization (or room correction) problem has been treated primarily by single-channel methods, where loudspeaker input signals are prefiltered individually by separate scalar filters. Single-channel methods are generally able to improve the average spectral flatness of the acoustic transfer functions in a listening region, but they cannot reduce the variability of the transfer functions within the region. Most modern audio reproduction systems, however, contain two or more loudspeakers, and in this paper we aim at improving the equalization performance by using all available loudspeakers jointly. To this end we propose a polynomial based MIMO formulation of the equalization problem. The new approach, which is a generalization of an earlier single-channel approach by the authors, is found to reduce the average reproduction error and the transfer function variability over a region in space. Moreover, pre-ringing artifacts are avoided, and the reproduction error below 1000 Hz is significantly reduced with an amount that scales with the number of loudspeakers used.

Keyword
Acoustic signal processing, acoustic modeling, loudspeakers, MIMO, equalizers, sound fields, multichannel audio
National Category
Natural Sciences Engineering and Technology
Research subject
Electrical Engineering with specialization in Signal Processing
Identifiers
urn:nbn:se:uu:diva-198367 (URN)10.1109/TASL.2013.2245650 (DOI)000316198800008 ()
Available from: 2013-04-15 Created: 2013-04-15 Last updated: 2017-12-06Bibliographically approved
Bahne, A., Brännmark, L.-J. & Ahlén, A. (2013). Symmetric loudspeaker-room equalization utilizing a pairwise channel similarity criterion. IEEE Transactions on Signal Processing, 61(24), 6276-6290.
Open this publication in new window or tab >>Symmetric loudspeaker-room equalization utilizing a pairwise channel similarity criterion
2013 (English)In: IEEE Transactions on Signal Processing, ISSN 1053-587X, E-ISSN 1941-0476, Vol. 61, no 24, 6276-6290 p.Article in journal (Refereed) Published
Abstract [en]

Similarity of the room transfer functions (RTFs) of symmetric channel pairs is crucial for correct sound reproduction of, for example, stereophonic or 5.1 surround multichannel recordings. This physical and psychoacoustical insight yielded the filter design framework presented in this paper. The filter design framework introduced is based on MIMO feedforward control. It has the aim of pairwise equalization of two audio channels and incorporates two features. In the first place, each channel is individually equalized by minimizing the difference between a desired target response and the original RTF by means of support loudspeakers. The second and novel feature represents the similarity requirement and aims at minimizing the difference between the compensated RTFs of the two channels. In order to asses the proposed method a measure of RTF similarity is proposed. Tests with measurements of two different multichannel audio systems proved the method to be able to significantly improve the similarity of two RTFs.

National Category
Engineering and Technology
Research subject
Electrical Engineering with specialization in Signal Processing
Identifiers
urn:nbn:se:uu:diva-211854 (URN)10.1109/TSP.2013.2281787 (DOI)000327259500012 ()
Available from: 2013-12-02 Created: 2013-12-02 Last updated: 2017-12-06Bibliographically approved
Berthilsson, S., Barkefors, A., Brännmark, L.-J. & Sternad, M. (2012). Acoustical zone reproduction for car interiors using a MIMO MSE framework.. In: AES 48th International Conference, Munich, Germany. Paper presented at AES 48th International Conference, Munich, Germany. .
Open this publication in new window or tab >>Acoustical zone reproduction for car interiors using a MIMO MSE framework.
2012 (English)In: AES 48th International Conference, Munich, Germany, 2012Conference paper, Published paper (Refereed)
National Category
Signal Processing
Research subject
Electrical Engineering with specialization in Signal Processing
Identifiers
urn:nbn:se:uu:diva-181006 (URN)
Conference
AES 48th International Conference, Munich, Germany
Available from: 2012-09-14 Created: 2012-09-14 Last updated: 2012-09-26
Bahne, A., Brännmark, L.-J. & Ahlén, A. (2012). Improved loudspeaker-room equalization for stereo systems regarding channel similarity. In: Proceedings - International Conference on Audio, Language and Image Processing. Paper presented at 3rd IEEE/IET International Conference on Audio, Language and Image Processing, ICALIP, Shanghai, CHINA (pp. 254-259). .
Open this publication in new window or tab >>Improved loudspeaker-room equalization for stereo systems regarding channel similarity
2012 (English)In: Proceedings - International Conference on Audio, Language and Image Processing, 2012, 254-259 p.Conference paper, Published paper (Refereed)
Abstract [en]

In this paper, a new approach to robust singlechannel loudspeaker-room equalization for stereo systems based on psychoacoustic insights is presented. Traditionally, in single-channel equalization each channel is equalized individually according to a desired target. In case the target cannot be reached for at least one of the two channels, this approach results in different loudspeaker-room transfer functions of the two channels at the listening position. However, reproducing the intended sound image of stereo recordings requires equal acoustic transfer functions from the input to the two loudspeakers to the listening region. In this paper we aim not only at equalizing the individual channels according to a desired target, but also at explicitly requiring symmetry between the two channels of a stereo system. To this end we propose a two-channel similarity SIMO controller structure, which is an extension to an earlier approach by the authors. The new approach is evaluated based on measurements in a room and is found to reduce differences between the room transfer functions of the two channels in both frequency and time domain.

National Category
Signal Processing
Research subject
Electrical Engineering with specialization in Signal Processing
Identifiers
urn:nbn:se:uu:diva-181052 (URN)10.1109/ICALIP.2012.6376621 (DOI)978-146730171-8 (ISBN)
Conference
3rd IEEE/IET International Conference on Audio, Language and Image Processing, ICALIP, Shanghai, CHINA
Available from: 2012-09-17 Created: 2012-09-17 Last updated: 2013-02-26Bibliographically approved
Brännmark, L.-J., Bahne, A. & Ahlén, A. (2012). Improved loudspeaker-room equalization using multiple loudspeakers and MIMO feedforward control. In: Acoustics, Speech and Signal Processing (ICASSP), 2012 IEEE International Conference. Paper presented at IEEE International Conference on Acoustics, Speech and Signal Processing, ICASSP, 25-30 March, 2012, Kyoto, Japan (pp. 237-240). .
Open this publication in new window or tab >>Improved loudspeaker-room equalization using multiple loudspeakers and MIMO feedforward control
2012 (English)In: Acoustics, Speech and Signal Processing (ICASSP), 2012 IEEE International Conference, 2012, 237-240 p.Conference paper, Published paper (Refereed)
Abstract [en]

In this paper, a new multichannel approach to robust loudspeaker-room equalization is presented. Traditionally, the equalization (or room correction) problem has been treated mostly by single-channel methods, with loudspeaker signals being prefiltered individually by separate scalar filters. Single-channel methods can generally improve the average spectral flatness of the acoustic transfer functions in a listening region, but the variability of the transfer functions within the region cannot be affected. Most modern audio reproduction systems, however, contain two or more loudspeakers, and in this paper we aim at improving the equalization performance by using all available loudspeakers jointly. To this end we propose a general MIMO formulation of the problem, which is a multichannel generalization of an earlier single-channel approach by the authors. The new approach is found to reduce the average reproduction error and the spatial variability of the acoustic transfer functions. Moreover, pre-ringing artifacts are avoided, and the reproduction error below 1000 Hz is significantly reduced with an amount that scales with the number of loudspeakers used.

National Category
Signal Processing
Research subject
Electrical Engineering with specialization in Signal Processing
Identifiers
urn:nbn:se:uu:diva-181012 (URN)10.1109/ICASSP.2012.6287861 (DOI)000312381400059 ()978-1-4673-0044-5 (ISBN)
Conference
IEEE International Conference on Acoustics, Speech and Signal Processing, ICASSP, 25-30 March, 2012, Kyoto, Japan
Available from: 2012-09-14 Created: 2012-09-14 Last updated: 2013-02-18Bibliographically approved
Lingvall, F. & Brännmark, L.-J. (2009). Multiple-point statistical room correction for audio reproduction: Minimum mean square error correction filtering. Journal of the Acoustical Society of America, 125(4), 2121-2128.
Open this publication in new window or tab >>Multiple-point statistical room correction for audio reproduction: Minimum mean square error correction filtering
2009 (English)In: Journal of the Acoustical Society of America, ISSN 0001-4966, E-ISSN 1520-8524, Vol. 125, no 4, 2121-2128 p.Article in journal (Refereed) Published
Abstract [en]

This paper treats the problem of correction of loudspeaker and room responses using a single source. The objective is to obtain a linear correction filter, which is robust with respect to listener movement within a predefined region-of-interest. The correction filter is based   on estimated impulse responses, obtained at several positions, and a linear minimum mean squared error criteria. The impulse responses are estimated using a Bayesian approach that takes both model errors and measurement noise into account, which results in reliable impulse response estimates and a measure of the estimation errors. The correction filter is then constructed by using information from both the estimated impulse response coefficients and their associated estimation errors. Furthermore, in the optimization criteria a time-dependent reflection filter is introduced, which attenuates the high frequency parts of the reflected responses, that is, the parts of the responses that cannot be compensated with a single source system. The resulting correction filter is shown to significantly improve both   the temporal and spectral properties of the responses compared to the uncorrected system, and, furthermore, the obtained correction filter has a low level of pre-ringing.

National Category
Signal Processing
Research subject
Electrical Engineering with specialization in Signal Processing
Identifiers
urn:nbn:se:uu:diva-111462 (URN)10.1121/1.3075615 (DOI)000265838000042 ()
Available from: 2009-12-15 Created: 2009-12-15 Last updated: 2017-12-12Bibliographically approved
Brännmark, L.-J. (2009). Robust audio precompensation with probabilistic modeling of transfer function variability. In: 2009 IEEE Workshop on Applications of Signal Processing to Audio and Acoustics (WASPAA2009), New York City, NY: . Paper presented at 2009 IEEE Workshop on Applications of Signal Processing to Audio and Acoustics (WASPAA2009), New York City, NY. .
Open this publication in new window or tab >>Robust audio precompensation with probabilistic modeling of transfer function variability
2009 (English)In: 2009 IEEE Workshop on Applications of Signal Processing to Audio and Acoustics (WASPAA2009), New York City, NY, 2009Conference paper, Published paper (Refereed)
National Category
Signal Processing
Research subject
Electrical Engineering with specialization in Signal Processing
Identifiers
urn:nbn:se:uu:diva-111480 (URN)
Conference
2009 IEEE Workshop on Applications of Signal Processing to Audio and Acoustics (WASPAA2009), New York City, NY
Available from: 2009-12-15 Created: 2009-12-15 Last updated: 2016-04-14Bibliographically approved
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