Microphone array signal processing for robot audition

Robot audition for humanoid robots interacting naturally with humans in an unconstrained real-world environment is a hitherto unsolved challenge. The recorded microphone signals are usually distorted by background and interfering noise sources (speakers) as well as room reverberation. In addition, the movements of a robot and its actuators cause ego-noise which degrades the recorded signals significantly. The movement of the robot body and its head also complicates the detection and tracking of the desired, possibly moving, sound sources of interest. This paper presents an overview of the concepts in microphone array processing for robot audition and some recent achievements

The catalytic activity of the endoplasmic reticulum-resident protein microsomal epoxide hydrolase towards carcinogens is retained on inversion of its membrane topology

Diol epoxides formed by the sequential action of cytochrome P-450 and the microsomal epoxide hydrolase (mEH) in the endoplasmic reticulum (ER) represent an important class of ultimate carcinogenic metabolites of polycyclic aromatic hydrocarbons. The role of the membrane orientation of cytochrome P-450 and mEH relative to each other in this catalytic cascade is not known. Cytochrome P-450 is known to have a type I topology. According to the algorithm of Hartman, Rapoport and Lodish [(1989) Proc. Natl. Acad. Sci. U.S.A. 86, 5786-5790], which allows the prediction of the membrane topology of proteins, mEH should adopt a type II membrane topology. Experimentally, mEH membrane topology has been disputed. Here we demonstrate that, in contrast with the theoretical prediction, the rat mEH has exclusively a type I membrane topology. Moreover we show that this topology can be inverted without affecting the catalytic activity of mEH. Our conclusions are supported by the observation that two mEH constructs (mEHg1 and mEHg2), containing engineered potential glycosylation sites at two separate locations after the C-terminal site of the membrane anchor, were not glycosylated in fibroblasts. However, changing the net charge at the N-terminus of these engineered mEH proteins by +3 resulted in proteins (++mEHg1 and ++mEHg2) that became glycosylated and consequently had a type II topology. The sensitivity of these glycosylated proteins to endoglycosidase H indicated that, like the native mEH, they are still retained in the ER. The engineered mEH proteins were integrated into membranes as they were resistant to alkaline extraction. Interestingly, an insect mEH with a charge distribution in its N-terminus similar to ++mEHg1 has recently been isolated. This enzyme might well display a type II topology instead of the type I topology of the rat mEH. Importantly, mEHg1, having the natural cytosolic orientation, as well as ++mEHg1, having an artificial huminal orientation, displayed rather similar substrate turnovers for the mutagenic metabolite benzo[a]pyrene 4,5-oxide. To our knowledge this is the first report demonstrating that topological inversion of a protein within the membrane of the ER has only a moderate effect on its enzymic activity, despite differences in folding pathways and redox environments on each side of the membrane. This observation represents an important step in the evaluation of the influence of mEH membrane orientation in the cascade of events leading to the formation of ultimate carcinogenic metabolites, and for studying the general importance of metabolic channelling on the surface of membranes

Blind Speech Deconvolution via Pretrained Polynomial Dictionary and Sparse Representation. 18th Pacific-Rim Conference on Multimedia, Harbin, China, September 28-29, 2017

Blind speech deconvolution aims to estimate both the source speech and acoustic channel from the convolutive reverberant speech. The problem is ill-posed and underdetermined, which often requires prior knowledge for the estimation of the source and channel. In this paper, we propose a blind speech deconvolution method via a pretrained polynomial dictionary and sparse representation. A polynomial dictionary learning technique is employed to learn the dictionary from room impulse responses, which is then used as prior information to estimate the source and the acoustic impulse responses via an alternating optimization strategy. Simulations are provided to demonstrate the performance of the proposed method

Near-Perfect Reconstruction Oversampled Nonuniform Cosine-Modulated Filter Banks Based on Frequency Warping and Subband Merging

A novel method for designing near-perfect reconstruction oversampled nonuniform cosine-modulated filter banks is proposed, which combines frequency warping and subband merging, and thus offers more flexibility than known techniques. On the one hand, desirable frequency partitionings can be better approximated. On the other hand, at the price of only a small loss in partitioning accuracy, both warping strength and number of channels before merging can be adjusted so as to minimize the computational complexity of a system. In particular, the coefficient of the function behind warping can be constrained to be a negative integer power of two, so that multiplications related to allpass filtering can be replaced with more efficient binary shifts. The main idea is accompanied by some contributions to the theory of warped filter banks. Namely, group delay equalization is thoroughly investigated, and it is shown how to avoid significant aliasing by channel oversampling. Our research revolves around filter banks for perceptual processing of sound, which are required to approximate the psychoacoustic scales well and need not guarantee perfect reconstruction