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  • 1. Berggren, Magnus
    et al.
    Borgh, Markus
    Schuldt, Christian
    Lindström, Fredric
    Claesson, Ingvar
    Low-complexity network echo cancellation approach for systems equipped with external memory2011In: IEEE Transactions on Audio, Speech, and Language Processing, ISSN 1558-7916, E-ISSN 1558-7924, Vol. 19, no 8, p. 2506-2515Article in journal (Refereed)
    Abstract [en]

    Long delays and sparseness characterize impulse responses in telecommunication networks and a vast number of solutions for network echo cancellation have been proposed over the years. In this paper, an approach for detecting dispersive regions of a sparse impulse response and a proportionate normalized least mean square (PNLMS)-based selective updating approach are combined with an adaptive double-talk detector to form a complete solution for echo cancellation. The proposed solution has low computational complexity and is targeted for systems equipped with external memory.

  • 2. Berggren, Magnus
    et al.
    Lindström, Fredric
    Waye, Kerstin Persson
    Claesson, Ingvar
    Analysis of How the Noise Level Depends on Different Activities in a Child Day-Care Center2008Conference paper (Refereed)
    Abstract [en]

    In child day-care centers the noise level can rise to high levels and in some cases become so high that the people present risk hearing damage. The purpose of this investigation was to study how the noise level depends on the different activities during the day. The study was performed at a child day-care center and 6 children and 5 adult female teachers participated. The participants had a microphone attached next to the ear connected to a wearable digital recorder. A total of 32.5 hours of data was recorded. By listening tests the recorded data could be sorted by activity and by number of people present in the same room as the test subject. Activities were classified as belonging to one of the following: outdoor activity, indoor play, singing, storytelling and gathering. Further, by listening, the data was classified in small group/large group (3 or less/more than 3). The results show that the average noise level (LAeq) for outdoor activity was the highest and was measured to 88.1 dBA (average over 7h52min). Singing was 81.5 dBA (1h26min), indoor play 81.3 dBA (19h21min), storytelling 76.6 dBA (1h09min) and gathering 75.0 dBA (2h44min). The noise level difference between all activities except between singing and indoor play and gathering and storytelling could be verified using t-test (p<0.001). Further, the results showed that the average noise level was 86.6 dBA (14h11min) for the large group and 79.6 dBA (18h21min) for the small group. This difference, of 7.0 dB was statistically validated (p<0.001) using t-test.

  • 3. Berggren, Magnus
    et al.
    Stjernberg, Louise
    Lindström, Fredric
    Claesson, Ingvar
    Audio Processing Solution for Video Conference Based Aerobics2010Conference paper (Refereed)
    Abstract [en]

    In this paper an audio processing solution for video conference based aerobics is presented. The proposed solution leaves the workout music unaltered by separating it from the speech and processing each signal separately. The speech signal processing is also performed at a lower sample rate, which saves computational power. Real time evaluation of the system shows that high quality music as well as a good two-way communication is maintained during the aerobic session.

  • 4. Borgh, Markus
    et al.
    Berggren, Magnus
    Schüldt, Christian
    Lindström, Fredric
    Claesson, Ingvar
    An improved adaptive gain equalizer for noise reduction with low speech distortion2011In: EURASIP Journal on Audio, Speech, and Music Processing, ISSN 1687-4714, E-ISSN 1687-4722, Vol. 7Article in journal (Refereed)
    Abstract [en]

    In high-quality conferencing systems, it is desired to perform noise reduction with as limited speech distortion as possible. Previous work, based on time varying amplification controlled by signal-to-noise ratio estimation in different frequency subbands, has shown promising results in this regard but can suffer from problems in situations with intense continuous speech. Further, the amount of noise reduction cannot exceed a certain level in order to avoid artifacts. This paper establishes the problems and proposes several improvements. The improved algorithm is evaluated with several different noise characteristics, and the results show that the algorithm provides even less speech distortion, better performance in a multi-speaker environment and improved noise suppression when speech is absent compared with previous work.

  • 5.
    Magnus, Berggren
    et al.
    Blekinge Institute of Technology, School of Engineering, Department of Electrical Engineering.
    Nilsson, Kristian
    Blekinge Institute of Technology, School of Engineering, Department of Electrical Engineering.
    Håkansson, Lars
    Blekinge Institute of Technology, School of Engineering, Department of Electrical Engineering.
    Agnesson, Helen
    Hedsten, Stefan
    Noise measurements in incubators at neonatal intensive care unit2012Conference paper (Refereed)
    Abstract [en]

    The purpose of this study was to investigate the noise properties and levels of common noise sources in a neonatal intensive care unit (NICU) and in particular inside and around an incubator. Many previous studies have been made on noise levels in NICU, frequently focusing on A-weighted sound levels. In this study it was not assumed that infant's hearing follows the same equal loudness curve as adults and hence instead of A-weighting, short time averaged sound spectra in the frequency range 20 Hz to 20 kHz was logged to identify the frequency distribution of specific noise generating events. It was seen that alarms and CPAP air-flow increased the noise level by up to 8 dB outside but was barely noticed inside when considering the un-weighted noise level. However, by analyzing individual frequencies, most events were noticeable inside the incubator. For instance, frequencies above 1 kHz were increased by 10 dB inside and 11 dB outside the incubator when CPAP was turned on. Opening and closing the incubator increased the un-weighted noise level by 8 dB inside and 7 dB outside.

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