Hervé Lissek

École Polytechnique Fédérale de Lausanne | EPFL · Signal Processing Laboratory LTS2

A transmission-line acoustic metamaterial is an engineered, periodic arrangement of relatively small unit-cells, the acoustic properties of which can be manipulated to achieve anomalous physical behaviours. These exotic properties open the door to practical applications, such as an acoustic leaky-wave antenna, through the implementation of radiatin...

The optical dispersive prism is a well-studied element, which allows separating white light into its constituent spectral colors, and stands in nature as water droplets. In analogy to this definition, the acoustic dispersive prism should be an acoustic device with capability of splitting a broadband acoustic wave into its constituent Fourier compon...

A one-dimensional acoustic negative refractive index metamaterial based on the transmission line approach is presented. This structure implements the dual transmission line concept extensively investigated in microwave engineering. It consists of an acoustic waveguide periodically loaded with membranes realizing the function of series “capacitances...

The acoustic impedance at the diaphragm of an electroacoustic transducer can be varied using a range of basic electrical control strategies, amongst which are electrical shunt circuits. These passive shunt techniques are compared to active acoustic feedback techniques for controlling the acoustic impedance of an electroacoustic transducer. The form...

Head tracking combined with head movements have been shown to improve auditory ex-ternalization of a virtual sound source and contribute to the performance in localization. With certain technically constrained head-tracking algorithms, as can be found in wearable devices, artefacts can be encountered. Typical artefacts could consist of an estimatio...

An acoustic dimer composed of two electronically controlled electroacoustic resonators is presented with the view of exploring one-dimensional topological phenomena. Active control allows real-time manipulation of the metamaterial’s properties, including its mechanical mass, resistance, compliance, and internal coupling. The latter enables active t...

An acoustic dimer composed of two electronically controlled electro-acoustic resonators is presented in view of exploring one-dimensional topological phenomena.

Controlling audible sound requires inherently broadband and subwavelength acoustic solutions, which are to date, crucially missing. This includes current noise absorption methods, such as porous materials or acoustic resonators, which are typically inefficient below 1 kHz, or fundamentally narrowband. Here, we solve this vexing issue by introducing...

Reciprocity guarantees that in most media, sound transmission is symmetric between two points of space when the location of the source and receiver are interchanged. This fundamental law can be broken in non-linear media, often at the cost of detrimental input power levels, large insertion losses, and ideally prepared single-frequency input signals...

Waves, such as light and sound, inherently bounce and mix due to multiple scattering induced by the complex material objects that surround us. This scattering process severely scrambles the information carried by waves, challenging conventional communication systems, sensing paradigms, and wave-based computing schemes. Here, we show that instead of...

This paper presents an acoustic impedance control architecture for an electroacoustic absorber combining both feedforward and feedback microphone-based strategies on a current-driven loudspeaker. Feedforward systems enable good performance for direct impedance control. However, inaccuracies in the required actuator model can lead to a loss of passi...

This paper is focused on experimental characterization of new active liners technologies in acoustic flow duct facilities (FDF). These measurements have been performed in the NLR (Netherlands Aerospace Center). Different configurations of passive and active treatments have been tested using the same grazing flow conditions (Mach 0.3) in an aeroacou...

The estimation of the orientation of an object, and a human head in particular, can be defined by the Euler angles: the yaw, pitch and roll. The robust and drift-free estimation of those angles is usually achieved with the data from several sensors such as accelerometers, gyroscopes and magnetometers, processed with sensor fusion algorithms. Howeve...

Controlling audible sound requires inherently broadband and subwavelength acoustic solutions, which are to date, crucially missing. This includes current noise absorption methods, such as porous materials or acoustic resonators, which are typically inefficient below 1 kHz, or fundamentally narrowband. Here, we solve this vexing issue by introducing...

The pressure-based, current-driven impedance control technique known as “Electroacoustic Absorption” has offered new horizons for room modal equalization at low frequencies, steerable anomalous reflection, acoustic transmission attenuation and non-reciprocal wave propagation. Nevertheless, its level of performance is strongly limited by stability c...

The design and the grazing flow aeroacoustical characterization of a 2D active liner based on an array of electroacoustic absorbers are presented in this paper. The strategy stands on a pressure-based, current-driven digital architecture for impedance control with both local and non local architectures. A wind tunnel test rig is used for the in-flo...

Sound absorption at low frequencies still remains a challenge in both scientific research and engineering practice. Natural porous materials are ineffective in this frequency range, as well as acoustic resonators which present too narrow bandwidth of absorption, thus requiring alternative solutions based on active absorption techniques. In the pres...

In the majority of active sound absorbing systems, a conventional electrodynamic loudspeaker is used as a controlled source. However, particular situations may require an actuator that is more resistant to harsh environments, adjustable in shape, and lighter. In this work, a plasma-based electroacoustic actuator operating on the atmospheric corona...

This work focuses on the development of a plasma-based electroacoustic transducer for active noise control applications. The transducer is based on the atmospheric corona discharge in a wire-to-mesh geometry. The main motivation for plasma technology is its simple robust design and absence of moving parts in the actuator, which could be advantageou...

In the majority of active sound absorbing systems, a conventional electrodynamic loudspeaker is used as a controlled source. However, particular situations may require an actuator that is more resistant to harsh environments, adjustable in shape, and lighter. In this work, a plasma-based electroacoustic actuator operating on the atmospheric corona...

Sound absorption at low frequencies still remains a challenge in both scientific research and engineering practice. Natural porous materials are ineffective in this frequency range, as well as acoustic resonators which present too narrow bandwidth of absorption, thus requiring alternative solutions based on active absorption techniques. In the pres...

This paper presents an impedance control architecture for an electroacoustic absorber combining both a feedforward and feedback microphone-based system on a current driven loudspeaker. Feedforward systems enable good performance for direct impedance control. However, inaccuracies in the required actuator model can lead to a loss of passivity, which...

In binaural sound reproduction, it has been shown that externalization improves the listening comfort. Using individualized binaural room impulse responses, it is possible to simulate sound sources in a given room for a listener wearing headphones. However, in some real-time binaural sound applications such as miniaturized hearables, it is not alwa...

Active electroacoustic absorption is an efficient way to reduce noise propagation in cavities and ducts and is a promising technology for aircraft engine noise reduction. Hybrid sensor-/shunt-based impedance control has proved effective but requires a most accurate model of the electroacoustic actuator. Alternatively, by sensing the pressure on the...

Conventional loudspeakers generate sound through the vibration of a diaphragm, attached to a rigid frame through elastic suspensions. Although such construction is satisfactory for sound diffusion in steady environments, it is likely to fail in harsh conditions, which is often the case for active noise control applications. Plasma-based actuators a...

The SALUTE project aims at evaluating performance of metacomposites for acoustic smart lining in grazing turbulent flow. Theoretical and numerical investigations are carried out for designing innovative specimen. A specific focus is placed in the realization of prototypes for evaluating the metacomposite liner performances in 2D and 3D liners, its...

An accurate knowledge of the sound field distribution inside a room is required to identify and optimally locate corrective measures for room acoustics. However, the spatial recovery of the sound field would result in an impractically high number of microphones in the room. Fortunately, at low frequencies, the possibility to rely on a sparse descri...

The absorption of airborne noise at frequencies below 300 Hz is a particularly vexing problem due to the absence of natural sound-absorbing materials at these frequencies. The prevailing solution for low-frequency sound absorption is the use of passive narrow-band resonators, the absorption level and bandwidth of which can be further enhanced using...

The auditory system allows the estimation of the distance to sound-emitting objects using multiple spatial cues. In virtual acoustics over headphones, a prerequisite to render auditory distance impression is sound externalization, which denotes the perception of synthesized stimuli outside of the head. Prior studies have found that listeners with m...

Acoustic resonators play a key role in the development of subwavelength-sized technologies capable of interacting with airborne audible sound, from its emission and absorption to its manipulation and processing. Specifically, artificial acoustic media made from an ensemble of subwavelength resonators, namely, acoustic metamaterials and metasurfaces...

Absorbing airborne noise at frequencies below 300 Hz is a particularly vexing problem due to the absence of natural sound absorbing materials at these frequencies. The prevailing solution for low-frequency sound absorption is the use of passive narrow-band resonators, whose absorption level and bandwidth can be further enhanced using nonlinear effe...

Sound field reconstruction in rooms is a subject of high interest in the domain of acoustic research. At low frequencies, a thorough understanding of sound field distribution is the key to identifying imbalance and irregularities caused by the room which will eventually lead to the coloration of sounds. Traditionally, an accurate rendering of the s...

The auditory system enables listeners to estimate the localization of auditory events resorting notably to individual binaural cues and room reflections reaching the eardrum. For hearing-impaired listeners using hearing aids, those cues are possibly distorted or not available in various situations such as remote microphone systems. This can make au...

This communication proposes an electromechano-acoustic absorber model that couples three physical domains using plate vibration and sound radiation theories. The mechanical system is an elastically suspended plate specifically developed to favor the piston-like movement thereof. An electromechanical transducer is attached to the plate in order to t...

Quiet zones and other sound zones have been a strong topic of research for some time, due to the interest of creating separate sound environments in a same room, in a large open-space office for example. A number of solutions have been proposed over the last years. This paper further investigates the solution proposed by Boulandet et al. in 2017, g...

When waves impinge on a disordered material they are back-scattered and form a highly complex interference pattern. Suppressing any such distortions in the free propagation of a wave is a challenging task with many applications in a number of different disciplines. In a recent theoretical proposal, it was pointed out that both perfect transmission...

Characterization of sound fields in rooms has always been a challenging task. A faithful reconstruction of sound fields in rooms generally would require an impractically high number of microphones. At low frequencies, where sound field can be modeled as a finite superposition of modes, a combination of Matching Pursuit (MP) and Least-squares optimi...

Enhancing speech intelligibility for hearing-impaired subjects in complex acoustic conditions is still a challenging topic of research. To mitigate the detrimental effects of background noise and reverberation, current hearing instruments incorporate various hardware and software strategies, among which speech enhancement algorithms are of primary...

Beamforming is commonly used in devices such as in hearing instruments (HI) with a view to reducing noise. It consists in focusing on audio signals arising from a prescribed steering direction while suppressing those coming from other directions. The efficiency of beamformers on speech intelligibility has been demonstrated in various studies. Never...

Abstract This paper deals with active sound attenuation in lined ducts with flow and its application to duct modes damping in aircraft engine nacelles. It presents an active lining concept based on an arrangement of electroacoustic absorbers flush mounted in the duct wall. Such feedback-controlled loudspeaker membranes are used to achieve locally r...

We introduce an active concept for achieving acoustic metasurfaces with steerable reflection properties, effective over a wide frequency band. The proposed active acoustic metasurface consists of a surface array of subwavelength loudspeaker diaphragms, each with programmable individual active acoustic impedances allowing for local control over the...

Little is known about the perception of artificial spatial hearing by hearing-impaired subjects. The purpose of this study was to investigate how listeners with hearing disorders perceived the effect of a spatialization feature designed for wireless microphone systems. Forty listeners took part in the experiments. They were arranged in four groups:...

Acoustical behavior of a room for a given position of microphone and sound source is usually described using the room impulse response. If we rely on the standard uniform sampling, the estimation of room impulse response for arbitrary positions in the room requires a large number of measurements. In order to lower the required sampling rate, some s...

We introduce an active concept for achieving acoustic metasurfaces with steerable reflection properties, effective over a wide frequency band. The proposed active acoustic metasurface consists in a surface array of subwavelength loudspeakers diaphragms, each with programmable individual active acoustic impedances allowing for local control over the...

Theory shows that waves with constant intensity can perfectly transmit through a disordered medium with a tailored distribution of gain and loss. We present the first experimental realization of this concept using an acoustic waveguide.

Electroacoustic absorbers represent an interesting solution for low-frequency sound absorption in rooms. These systems simply consist of closed-box electrodynamic loudspeakers, whose acoustic impedance at the diaphragm is judiciously adjusted by connecting a passive or active electrical control circuit. This paper presents a method for designing di...

Low-frequency electroacoustic absorbers have recently been developed as asolution for the modal equalisation. Firstly investigated in waveguides, the technique consists in matching the acoustic impedance at a closed-box loudspeaker diaphragm to the characteristic acoustic impedance of air. Extending the results in a duct to rooms brings up several...

We investigate the possibility for acoustic waves to propagate with a constant amplitude in disordered media. We find that this remarkable property is possible if one adds a tailored distribution of gain and loss on top of the disorder, making the medium non-Hermitian. We present the theory of constant-amplitude acoustic waves in both cases of cont...

This paper presents a local control approach to generate remote quiet zones. To deal with situations where global control can hardly be achieved, it is proposed to use an arrangement of spot-type sound reducers as originally suggested by Olson and May. Assuming that cross-coupling between control units is weak, each can be controlled independently...

Recent studies have focused on developing metamaterials for acoustic applications, inspired by electromagnetics concepts. The acoustic leaky-wave antenna is amongst the most investigated. Despite the unfavourable properties of conventional matter and structures with respect to sound dispersion and radiation, interesting engineering processes have b...

Estimation of the location of sound sources is usually done using microphone arrays. Such settings provide an environment where we know the difference between the received signals among different microphones in the terms of phase or attenuation, which enables localization of the sound sources. In our solution we exploit the properties of the room t...

In animal communication, signal loudness is often ignored and seldom measured. We used a playback experiment to examine the role of vocal loudness (i.e., sound pressure level) in sibling to sibling communication of nestling barn owls Tyto alba. In this species, siblings vocally negotiate among each other for priority access to parental food resourc...

Acoustic liners are a widespread solution to reduce turbofan noise in aircraft nacelles, due to lightweight and relatively small dimensions for integration within nacelles. Although conventional liners might be designed so as to target multiple tonal frequencies, their passive principle prevents the adaptation to varying engine speeds and therefore...

In order to address optimal acoustic control in rooms, an accurate characterization of the room shape and wall properties is required. There are only a few approaches that model the wall impedances. Most of them rely on finite difference time domain methods, which are limited to shoebox-shaped rooms and only valid at low frequencies (non-rectangula...

It has been shown that acoustic waves with helical wavefronts can carry angular momentum, which can be transmitted towards a propagating medium. Such a wave field can be achieved by using a planar array of electroacoustic transducers, forming a given spatial distribution of phased sound sources which produce the desired helical wavefronts. Here, we...

An acoustic metasurface carpet cloak based on membrane-capped cavities is proposed and investigated numerically. This design has been chosen for allowing ultrathin geometries, although adapted to airborne sound frequencies in the range of 1 kHz (λ≈30 cm), surpassing the designs reported in the literature in terms of thinness. A formulation of gener...

This paper presents a concept of sensorless electroacoustic absorber for damping the low-frequency modes in a cavity such as a duct or a room. Taking advantage of the reciprocity of the voice coil transducer, it is shown that a synthetic electrical admittance can be designed so that the loudspeaker diaphragm is matched to a target specific acoustic...

In listening rooms, low-frequency modal resonances lead to uneven distributions in space and frequency of the acoustic energy, as well as an alteration of the temporal behaviour of the original music content. While usual absorption techniques have severe limitations for reducing the negative impact of room modes, the authors have previously propose...

This paper proposes a hybrid impedance control architecture for an electroacoustic absorber, that combines an improved microphone-based feedforward control with a currentdriven electrodynamic loudspeaker system. Feedforward control architecture enables stable control to be achieved, and current driving method discards the effect of the voice coil i...