40 research outputs found
RTF-Based Binaural MVDR Beamformer Exploiting an External Microphone in a Diffuse Noise Field
Besides suppressing all undesired sound sources, an important objective of a
binaural noise reduction algorithm for hearing devices is the preservation of
the binaural cues, aiming at preserving the spatial perception of the acoustic
scene. A well-known binaural noise reduction algorithm is the binaural minimum
variance distortionless response beamformer, which can be steered using the
relative transfer function (RTF) vector of the desired source, relating the
acoustic transfer functions between the desired source and all microphones to a
reference microphone. In this paper, we propose a computationally efficient
method to estimate the RTF vector in a diffuse noise field, requiring an
additional microphone that is spatially separated from the head-mounted
microphones. Assuming that the spatial coherence between the noise components
in the head-mounted microphone signals and the additional microphone signal is
zero, we show that an unbiased estimate of the RTF vector can be obtained.
Based on real-world recordings, experimental results for several reverberation
times show that the proposed RTF estimator outperforms the widely used RTF
estimator based on covariance whitening and a simple biased RTF estimator in
terms of noise reduction and binaural cue preservation performance.Comment: Accepted at ITG Conference on Speech Communication 201
Comparison of Binaural RTF-Vector-Based Direction of Arrival Estimation Methods Exploiting an External Microphone
In this paper we consider a binaural hearing aid setup, where in addition to
the head-mounted microphones an external microphone is available. For this
setup, we investigate the performance of several relative transfer function
(RTF) vector estimation methods to estimate the direction of arrival(DOA) of
the target speaker in a noisy and reverberant acoustic environment. More in
particular, we consider the state-of-the-art covariance whitening (CW) and
covariance subtraction (CS) methods, either incorporating the external
microphone or not, and the recently proposed spatial coherence (SC) method,
requiring the external microphone. To estimate the DOA from the estimated RTF
vector, we propose to minimize the frequency-averaged Hermitian angle between
the estimated head-mounted RTF vector and a database of prototype head-mounted
RTF vectors. Experimental results with stationary and moving speech sources in
a reverberant environment with diffuse-like noise show that the SC method
outperforms the CS method and yields a similar DOA estimation accuracy as the
CW method at a lower computational complexity.Comment: Submitted to EUSIPCO 202
Wide-area monitoring and control of future smart grids
Application of wide-area monitoring and control for future smart grids with substantial
wind penetration and advanced network control options through FACTS and HVDC
(both point-to-point and multi-terminal) is the subject matter of this thesis.
For wide-area monitoring, a novel technique is proposed to characterize the system dynamic
response in near real-time in terms of not only damping and frequency but also
mode-shape, the latter being critical for corrective control action. Real-time simulation
in Opal-RT is carried out to illustrate the effectiveness and practical feasibility of the proposed
approach. Potential problem with wide-area closed-loop continuous control using
FACTS devices due to continuously time-varying latency is addressed through the proposed
modification of the traditional phasor POD concept introduced by ABB. Adverse
impact of limited bandwidth availability due to networked communication is established
and a solution using an observer at the PMU location has been demonstrated.
Impact of wind penetration on the system dynamic performance has been analyzed along
with effectiveness of damping control through proper coordination of wind farms and
HVDC links. For multi-terminal HVDC (MTDC) grids the critical issue of autonomous
power sharing among the converter stations following a contingency (e.g. converter outage)
is addressed. Use of a power-voltage droop in the DC link voltage control loops
using remote voltage feedback is shown to yield proper distribution of power mismatch
according to the converter ratings while use of local voltages turns out to be unsatisfactory.
A novel scheme for adapting the droop coefficients to share the burden according
to the available headroom of each converter station is also studied.
The effectiveness of the proposed approaches is illustrated through detailed frequency
domain analysis and extensive time-domain simulation results on different test systems
NASA Tech Briefs, March 1988
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