| 1681. |
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| 1682. |
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| 1683. |
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| 1684. |
- Larsson, Måns, 1989, et al.
(författare)
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A cross-season correspondence dataset for robust semantic segmentation
- 2019
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Ingår i: Proceedings of the IEEE Computer Society Conference on Computer Vision and Pattern Recognition. - 1063-6919. ; 2019-June, s. 9524-9534
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Konferensbidrag (refereegranskat)abstract
- In this paper, we present a method to utilize 2D-2D point matches between images taken during different image conditions to train a convolutional neural network for semantic segmentation. Enforcing label consistency across the matches makes the final segmentation algorithm robust to seasonal changes. We describe how these 2D-2D matches can be generated with little human interaction by geometrically matching points from 3D models built from images. Two cross-season correspondence datasets are created providing 2D-2D matches across seasonal changes as well as from day to night. The datasets are made publicly available to facilitate further research. We show that adding the correspondences as extra supervision during training improves the segmentation performance of the convolutional neural network, making it more robust to seasonal changes and weather conditions.
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| 1685. |
- Larsson, Martin, et al.
(författare)
-
A FEEDFORWARD ACTIVE NOISE CONTROL SYSTEM FOR DUCTS USING A PASSIVE SILENCER TO REDUCE ACOUSTIC FEEDBACK
- 2007
-
Konferensbidrag (refereegranskat)abstract
- Ventilation systems installed in buildings usually generate low-frequency noise because the passive silencers commonly used to attenuate the ventilation noise are not effective in the low-frequency range. A method proven to effectively reduce low-frequency noise in a wide variety of applications is active noise control (ANC). A feedforward ANC system applied to duct noise normally uses a reference microphone, a control unit, a loudspeaker to generate the secondary noise created by the controller, and an error microphone. The secondary noise generated by the loudspeaker will travel both downstream canceling the primary noise, and upstream to the reference microphone, i.e. acoustic feedback. The acoustic feedback may result in performance reduction and stability problems of the control system. Common approaches to solve the feedback problem result in more complex controller structures and/or system configurations than the simple feedforward controller, e.g. introducing a feedback cancellation filter in the controller in parallel with the acoustic feedback path, or using a dual-microphone reference sensing system. This paper presents a simple approach to reduce the acoustic feedback by using a basic feedforward controller in combination with a passive silencer. Simulations show that efficient acoustic feedback cancellation is achieved by using a passive silencer. In the experimental setup another advantage with using a passive silencer is that the frequency response function of the forward path, which is to be estimated, is smoother, i.e. most of the dominant frequency peaks in the frequency response function when not using a passive silencer is reduced. This in turn results in an acoustic path that is less complex to estimate with high accuracy using an adaptive FIR filter steered with the LMS algorithm.
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| 1686. |
- Larsson, Martin, et al.
(författare)
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A Module Based Active Noise Control System for Ventilation Systems, Part I : Influence of Measurement Noise on the Performance and Convergence of the Filtered-x LMS Algorithm
- 2009
-
Ingår i: International Journal of Acoustics and Vibration. - : International Institute of Acoustics and Vibration. - 1027-5851 .- 2415-1408. ; 14:4, s. 188-195
-
Tidskriftsartikel (refereegranskat)abstract
- Low noise level is an essential feature when installing ventilation systems today. To achieve attenuation over a broad frequency range, the passive silencers traditionally used to attenuate ventilation noise can be combined with an active noise control (ANC) system. To insure reliable operation and desirable levels of attenuation when applying ANC to duct noise, it is highly important to be able to suppress the contamination of the microphone signals due to the turbulent pressure fluctuations arising as the microphones are exposed to the airflow in the duct. This paper is the first in a series of two, that treats the problem of turbulence induced noise originating from the airflow inside the ducts. Part I is concerned with theoretical and experimental investigations of the influence of the turbulence induced noise on the adaptive algorithm in the ANC system. Part II is concerned with design and investigations of microphone installations for turbulence suppression and results concerning the performance of an ANC system with the different microphone installations are presented. Some of the results were obtained at an acoustic laboratory according to an ISO-standard. The attenuation achieved with ANC was approximately 15-25 dB between 50-315 Hz even for airflow speeds up to 20 m/s.
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| 1687. |
- Larsson, Martin, et al.
(författare)
-
A Module Based Active Noise Control System for Ventilation Systems, Part II : Performance Evaluation
- 2009
-
Ingår i: International Journal of Acoustics and Vibration. - : International Institute of Acoustics and Vibration. - 1027-5851 .- 2415-1408. ; 14:4, s. 196-206
-
Tidskriftsartikel (refereegranskat)abstract
- To utilize the full noise attenuation potential of an active noise control (ANC) system applied to duct noise, it is important to be able to minimize the turbulence induced noise in the microphone signals. This is the second paper in a series of two, that treats the problem of turbulence induced noise originating from the airflow inside the ducts, when applying ANC to ducts. Part I contains theoretical and experimental investigations of the influence of the turbulence induced noise on the filtered-x LMS algorithm used in the ANC system. Part II (the present paper) is concerned with design and investigations of microphone installations which produces a sufficient amount of turbulence suppression while also meeting industry requirements. These requirements are, for example, that the microphone installations should be based on standard ventilation parts, and that they should be easily installed and maintained. Furthermore, results concerning the performance of an ANC system with different microphone installations are presented. Some of the results were obtained at an acoustic laboratory according to an ISO standard. The attenuation achieved with ANC was approximately 15-25 dB between 50-315 Hz even for airflow speeds up to 20 m/s.
|
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| 1688. |
- Larsson, Martin, et al.
(författare)
-
A Module Based Active Noise Control System for Ventilation Systems, Part II : Performance Evaluation
- 2009
-
Ingår i: International Journal of Acoustics and Vibration. - : International Institute of Acoustics and Vibration (IIAV). - 1027-5851 .- 2415-1408. ; 14:4, s. 196-206
-
Tidskriftsartikel (refereegranskat)abstract
- To utilize the full noise-attenuation potential of an active noise control (ANC) system applied to duct noise, it is important to be able to minimize the turbulence-induced noise in the microphone signals. This is the second paper in a series of two, that treats the problem of turbulence-induced noise originating from the airflow inside the ducts, when applying ANC to ducts. Part I contains theoretical and experimental investigations of the influence of the turbulence-induced noise on the filtered-x LMS algorithm used in the ANC system. Part II (the present paper) is concerned with the design and investigations of microphone installations, which produce a sufficient amount of turbulence suppression while also meeting industry requirements. These requirements are, for example, that the microphone installations should be based on standard ventilation parts, and that they should be easily installed and maintained. Furthermore, results concerning the performance of an ANC system with different microphone installations are presented. Some of the results were obtained at an acoustic laboratory according to an ISO standard. The attenuation achieved with ANC was approximately 15-25 dB between 50-315 Hz, even for airflow speeds up to 20 m/s.
|
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| 1689. |
- Larsson, Martin, et al.
(författare)
-
A Module Based Active Noise ControlSystem for Ventilation Systems, Part I : Influence of Measurement Noise on the Performance and Con-vergence of the Filtered-x LMS Algorithm
- 2009
-
Ingår i: International Journal of Acoustics and Vibration. - : International Institute of Acoustics and Vibration (IIAV). - 1027-5851 .- 2415-1408. ; 14:4, s. 188-195
-
Tidskriftsartikel (refereegranskat)abstract
- Low noise level is an essential feature when installing ventilation systems today. To achieve attenuation over a broad frequency range, the passive silencers traditionally used to attenuate ventilation noise can be combined with an active noise control (ANC) system. To insure reliable operation and desirable levels of attenuation when applying ANC to duct noise, it is highly important to be able to suppress the contamination of the microphone signals due to the turbulent pressure fluctuations, which arise as the microphones are exposed to the airflow in the duct. This paper is the first in a series of two regarding the problem of turbulence-induced noise originating from the airflow inside the ducts. Part I is concerned with theoretical and experimental investigations of the influence of the turbulence-induced noise on the adaptive algorithm in the ANC system. Part II is concerned with the design and the investigations of microphone installations for turbulence suppression and the results concerning the performance of an ANC system with the different microphone installations are presented. Some of the results were obtained at an acoustic laboratory according to an ISO-standard. The attenuation achieved with ANC was approximately 15-25 dB between 50-315 Hz, even for airflow speeds up to 20 m/s
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| 1690. |
- Larsson, Matilda, et al.
(författare)
-
A novel measure to express tracking quality in ultrasound block matching
- 2010
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Ingår i: Proceedings - IEEE Ultrasonics Symposium. - 9781457703829 ; , s. 1636-1639
-
Konferensbidrag (refereegranskat)abstract
- Speckle de-correlation is a major problem in block matching based ultrasound methodologies as it limits the accuracy of the tracking result. It would be of benefit to have a quantitative measure expressing the local tracking quality as it would allow discarding unreliable motion estimates. We hypothesized that kernels showing sufficient gray scale pattern would more reliably track than kernels with more homogenous gray scale distributions. The aim of this study was to test this hypothesis in-silico. Ultrasound B-mode sequences were simulated from a kinematic model of the carotid artery. Two-dimensional motion was estimated using block matching with the normalized cross-correlation function as similarity measure. For each kernel, two measures of tracking quality were stored: the normalized cross-correlation coefficient (Ccc) and a measure of the amount of edges inside the kernel detected using a canny filter and counted on a pixel-by-pixel basis. As such, a quality measure (Cedge) between 0 (no edges) and 1 (nothing but edges) was obtained. Axial and lateral strains were subsequently obtained by linear regression in regions of interest (ROIs) with best/worst mean tracking quality scores. The root-mean-squared-error (RMSE) was significantly lower in regions with low Ccc (worst ROI) compared to ROIs with high Ccc. However, more edges in the kernel did indeed result in better overall tracking (lower RMSE). Thus, the proposed edge-detection method showed to be a better tracking quality measure than the commonly used Ccc.
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