Publications by Olivier Roy | EPFL Graph Search

Robust Array Calibration Using Time Delays with Application to Ultrasound Tomography

Martin Vetterli, Olivier Roy, Ivana Jovanovic

Accurate calibration is a requirement of many array signal processing techniques. We investigate the calibration of a transducer array using time delays. We derive a strategy based on the mean square error criterion and discuss how time delays that are not ...

2011

Distributed audio coding for wireless hearing aids

Martin Vetterli, Olivier Roy

The aim of the invention is to provide inter-channel level differences ICLD related to audio signals for hearing aids. This aim is achieved by a method for computing ICLD from a first and second audio source signals, the first source signal being wired wit ...

2011

Robust Ultrasound Travel-time Tomography Using the Bent Ray Model

Martin Vetterli, Olivier Roy, Ivana Jovanovic, Ali Hormati

We present a bent ray reconstruction algorithm for an ultrasound tomography (UT) scanner designed for breast screening. The scanner consists of a circular array of transmitters and receivers which encloses the object to be imaged. By solving a nonlinear sy ...

Spie-Int Soc Optical Engineering, Po Box 10, Bellingham, Wa 98227-0010 Usa2010

Sound Speed Estimation Using Wave-based Ultrasound Tomography: Theory and GPU Implementation

Martin Vetterli, Olivier Roy, Ivana Jovanovic, Ali Hormati, Reza Parhizkar

We present preliminary results obtained using a time domain wave-based reconstruction algorithm for an ultrasound transmission tomography scanner with a circular geometry. While a comprehensive description of this type of algorithm has already been given e ...

Spie-Int Soc Optical Engineering, Po Box 10, Bellingham, Wa 98227-0010 Usa2010

Distributed Sensing of Signals Linked by Sparse Filtering

Martin Vetterli, Olivier Roy, Ali Hormati, Yue Lu

Certain aspects of the present disclosure provide methods for distributed sensing and centralized reconstruction of two correlated signals, modeled as the input and output of an unknown sparse filtering operation. ...

2010

Distributed Sampling of Signals Linked by Sparse Filtering: Theory and Applications

Martin Vetterli, Olivier Roy, Ali Hormati, Yue Lu

We study the distributed sampling and centralized reconstruction of two correlated signals, modeled as the input and output of an unknown sparse filtering operation. This is akin to a Slepian-Wolf setup, but in the sampling rather than the lossless compres ...

2010

Distributed Sensing of Signals Linked by Sparse Filtering

Martin Vetterli, Olivier Roy, Ali Hormati, Yue Lu

We consider the task of recovering correlated vectors at a central decoder based on fixed linear measurements obtained by distributed sensors. A general formulation of the problem is proposed, under both a universal and an almost sure reconstruction requir ...

2009

Distributed Sensing of Signals under a Sparse Filtering Model

Martin Vetterli, Olivier Roy, Ali Hormati, Yue Lu

We consider the task of recovering correlated vectors at a central decoder based on fixed linear measurements obtained by distributed sensors. Two different scenarios are considered: In the case of universal reconstruction, we look for a sensing and recove ...

2009

Rate-Constrained Collaborative Noise Reduction for Wireless Hearing Aids

Martin Vetterli, Olivier Roy

Hearing aids are electronic, battery-operated sensing devices which aim at compensating various kinds of hearing impairments. Recent advances in low-power electronics coupled with progresses made in digital signal processing offer the potential for substan ...

2009

Dimensionality Reduction for Distributed Estimation in the Infinite Dimensional Regime

Martin Vetterli, Olivier Roy

Distributed estimation of an unknown signal is a common task in sensor networks. The scenario usually envisioned consists of several nodes, each making an observation correlated with the signal of interest. The acquired data is then wirelessly transmitted ...

Institute of Electrical and Electronics Engineers2008

Distributed signal processing for binaural hearing aids

Olivier Roy

Over the last centuries, hearing aids have evolved from crude and bulky horn-shaped instruments to lightweight and almost invisible digital signal processing devices. While most of the research has focused on the design of monaural apparatus, the use of a ...

EPFL2008

Time of flight estimation method using beamforming for acoustic tomography

Martin Vetterli, Olivier Roy, Ivana Jovanovic, Ali Hormati

It is disclosed an acoustic tomography method to improve the time of flight estimation, said method comprising the steps of: sequentially triggering a set of N transmitters so as to generate a sequence of N acoustic waves through a volume being scanned; re ...

2008

Distributed Spatial Audio Coding in Wireless Hearing Aids

Martin Vetterli, Olivier Roy

The information content of binaural signals can be beneficial to many algorithms deployed in current digital hearing aids. However, the exchange of such signals over a wireless communication link requires transmission schemes that must fulfill demanding te ...

2007

The Effective Rank: A Measure of Effective Dimensionality

Martin Vetterli, Olivier Roy

Many signal processing algorithms include numerical problems where the solution is obtained by adjusting the value of parameters such that a specific matrix exhibits rank deficiency. Since rank minimization is generally not practicable owing to its integer ...

2007

Spatio-Temporal Sampling and Distributed Compression of the Sound Field

Martin Vetterli, Robert Konsbruck, Luciano Sbaiz, Olivier Roy, Emre Telatar, Thibaut Ajdler

We investigate how the sound field induced by an acoustic event evolves over space and time. The characteristics of its bidimensional Fourier spectrum are analyzed and spatio-temporal sampling results using an array of microphones are provided for differen ...

2006

Rate-Constrained Beamforming for Collaborating Hearing Aids

Martin Vetterli, Olivier Roy

Hearing aids are audio capture devices which aim at providing the hearing impaired with better audibility. Most of the state-of-the-art systems involve sensing devices that work independently. However, the availability of a wireless communication link betw ...

2006

Collaborating Hearing Aids

Martin Vetterli, Olivier Roy

Hearing aids are electronic, battery-operated sensing devices which aim at compensating various kinds of hearing impairments by means of appropriate signal processing. Most of today's hearing aid systems consist of two appliances working independently of e ...

2006

Distributed Compression in Acoustic Sensor Networks Using Oversampled A/D Conversion

Martin Vetterli, Olivier Roy

We address the problem of distributed compression in acoustic sensor networks. A typical scenario consists of a set of microphones that record a sound source located at some unknown position. The goal then is to convey the corresponding audio signals to a ...

2006

On the Asymptotic Distortion Behavior of the Distributed Karhunen-Loève Transform

Martin Vetterli, Olivier Roy

The ability to design efficient distributed communications systems heavily depends on a proper understanding of the distortion incurred by their constituting elements. To this end, we study the mean squared reconstruction error behavior of the distributed ...

2005