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Identifier |
000381055 |
Title |
Directional coding of audio signals using a circular microphone array |
Alternative Title |
Κωδικοποίηση κατευθυντικής πληροφορίας ηχητικών σημάτων χρησιμοποιώντας μαι κυκλική συστοιχία μικροφώνων |
Author
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Αλεξανδρίδης, Αναστάσιος Ι
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Thesis advisor
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Μουχτάρης, Αθανάσιος
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Abstract |
Microphone arrays have attracted great attention in the last decades. The main reason is
their ability to perform sound source localization and beamforming. Moreover, based upon the
knowledge of sound propagation, microphone arrays have great potential in the field of noiserobust
speech capture and hands-free signal acquisition. Microphone arrays—and particularly
circular arrays—are already used in several modern speech communication systems, such as
teleconferencing and next generation hearing aids.
In this thesis, we focus on recording and reproducing the spatial characteristics of an arbitrary
sound field, and propose a new method for extracting and coding the directional information of
audio and speech signals using a circular array of microphones. Our method is computationally
efficient—it consumes approximately 50% of real-time—and thus is suitable for real-time implementations.
We model the sound field based on estimating the Direction-of-Arrival (DOA) of all
simultaneously active sound sources and separating the source signals through spatial filtering
with a fixed superdirective beamformer. In contrast to previous work, our DOA estimation procedure
is not based on a strict W-disjoint orthogonality assumption for the sound sources (i.e., we
do not assume that each time-frequency element is dominated by only one sound source), which
is expected to make the modelling of the sound field more accurate. The separated source signals
are downmixed into one audio signal, and as a result, the sound field is encoded using one monophonic
audio signal and side-information. To reduce the bitrate requirements, the monophonic
audio signal can be encoded with any compression algorithm, such as MP3. We also propose an
efficient lossless compression scheme for the side-information. The recorded sound field is reproduced
using amplitude panning for loudspeaker reproduction or Head-Related Transfer Function
(HRTF) filtering for reproduction via headphones.
In order to evaluate the performance of our proposed method, we conducted listening tests
using microphone array recordings in simulated and real environments. We considered both reproduction
over headphones and loudspeakers, while the recordings included both speech and
music signals of stationary and moving sources. Our approach was compared with other recently
proposed microphone array based methods for spatial audio. Our listening test results reveal
that our method achieves excellent reconstruction of the sound field while maintains the sound
quality at very high levels. Lastly, we investigated the effects of coding the audio signal with
an MP3 encoder and found that coding the downmixed signal at 64 kbps results in unnoticeable
degradation in the spatial impression and sound quality of the reconstructed sound field,
compared with not applying any compression.
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Language |
Greek, English |
Subject |
Beamforming |
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Spatial audio |
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Σχηματισμός λοβού |
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Χωρικός ήχος |
Issue date |
2013-07-19 |
Collection
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School/Department--School of Sciences and Engineering--Department of Computer Science--Post-graduate theses
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Type of Work--Post-graduate theses
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Permanent Link |
https://elocus.lib.uoc.gr//dlib/b/b/9/metadata-dlib-1383895130-102812-4712.tkl
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Views |
584 |