21 research outputs found
A generalized proportionate variable step-size algorithm for fast changing acoustic environments
This paper proposes a generalized proportionate variable step-size algorithm based on Affine projection. It controls the step size for each tap individually based on the gradient approximated by the difference between the current coefficient and an averaged filter coefficient with delay. This step-size control is specifically effective for tracking fast changing acoustic environments. It is shown that P-NLMS family and the ES algorithm are special cases of the proposed algorithm in terms of step-size control. Simulation results in the context of echo cancellation in artificial and real environments demonstrate that this step-size control combined with the Affine projection algorithm (APA) reduces the echo by up to 5 dB compared to the standard APA. The best tracking performance, without a priori knowledge on the acoustic environment, among the same family of algorithms is obtained
Optimal and Adaptive Microphone Arrays for Speech Input in Automobiles
In this chapter, speech enhancement and echo cancellation for hands-free mobile
telephony is discussed. A
number of microphone array methods have been tested and results from car
measurements are given. Traditional
methods such as linearly constrained beamforming and generalised sidelobe
cancellers are discussed as well as
array gain optimisation methods. An in-situ calibrated method which gives an
over all improved performance is
also presented. Algorithms such as LS and NLMS are used to find optimal
weights. The improved
performance using an LS-method is shown. This has however limitations in
realtime implementations because of
the numerical complexity. By introducing subband processing these limitations
can be avoided. The results show
a noise suppression of approximately 18 dB and hands-free loudspeaker
suppression of the same order