Publications related to Acoustic impedance

Impact of beam-coupling impedance on the Schottky spectrum of bunched beam

Tatiana Pieloni, Nicolas Frank Mounet, Christophe Emmanuel R. Lannoy

The Schottky monitors of the Large Hadron Collider (LHC) can be used for non-invasive beam diagnostics to estimate various bunch characteristics, such as tune, chromaticity, bunch profile or synchrotron frequency distribution. However, collective effects, ...

Iop Publishing Ltd2024

Acoustic Levitation apparatus (Robotics Practicals)

Mahmut Selman Sakar, Lorenzo Francesco John Noseda, Amit Yedidia Dolev, Bora Yalcin

The following data contain the information and files, which are required to recreate and build the experimental setup that is described in the Laboratory manual. Further details can be found in the associated publication “A graduate laboratory experiment t ...

Zenodo2023

Low frequency sound field reconstruction in a non-rectangular room using a small number of microphones

Hervé Lissek, Vu Thach Pham

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 microp ...

2020

Development of a plasma electroacoustic actuator for active noise control applications

Ivo Furno, Hervé Lissek, Alan Howling, Pénélope Leyland, Stanislav Sergeev, Gennady Plyushchev

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 condi ...

2020

Distributed analyses using distinct classes of Brillouin scatterings in optical fibres

Desmond Chow Ming Chia

Brillouin scattering is an interaction between light and sound in a material. This inelastic light scattering had been observed in the first optical fibres that were used in cross-continent communication. Via Brillouin scattering, the guided light wave in ...

EPFL2018

Room Modal Equalisation with Electroacoustic Absorbers

Etienne Thierry Jean-Luc Rivet

The sound quality in a room is of fundamental importance for both recording and reproducing processes. Because of the room modes, the distributions in space and frequency of the sound field are largely altered. Excessive rise and decay times caused by the ...

EPFL2016

Experimental assessment of low-frequency electroacoustic absorbers for room modal equalization in actual listening rooms

Hervé Lissek, Etienne Thierry Jean-Luc Rivet, Sami Driss Karkar, Véronique Adam

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 behavior of the original music content. While usual absorption techniques have severe li ...

AES2016

Through the Hourglass: A Faithful Audiovisual Reconstruction of the Old Montreux Casino

Martin Vetterli

In architecture, space is traditionally understood as a cumulus of forms, colors and textures that form a conceived area, or-in other words-architectural space design is mainly achieved by following visual concepts. The human experience of space, however, ...

Springer2015

Electroacoustic absorbers for the low-frequency modal equalization of a room: what is the optimal target impedance for maximum modal damping, depending on the total area of absorbers?

Hervé Lissek, Etienne Thierry Jean-Luc Rivet, Sami Driss Karkar, Véronique Adam

Electroacoustic absorbers consist of loudspeakers, shunted with an electrical circuit designed to obtain a given acoustic impedance. Their design and principles are now well understood. Unidimensional experiments, using plane waves under normal incidence i ...

2014

Equation of state of liquid mercury to 520 K and 7 GPa from acoustic velocity measurements

Livia Eleonora Bove Kado

Ultrafast acoustics measurements on liquid mercury have been performed at high pressure and temperature in a diamond anvil cell using picosecond acoustic interferometry. We extract the density of mercury from adiabatic sound velocities using a numerical it ...

American Institute of Physics2014

Design of a built-in electroacoustic resonator for active noise reduction

Hervé Lissek, Romain Boulandet, Etienne Thierry Jean-Luc Rivet

The paper focuses on the design of a built-in electroacoustic device for active noise reduction purposes. The device basically encompasses a loudspeaker connected to a synthetic electrical impedance that enhances its ability to dissipate part of the incomi ...

2013

Advanced control for modifying the acoustic impedance at the diaphragm of a loudspeaker

Hervé Lissek, Romain Boulandet, Etienne Thierry Jean-Luc Rivet

The control of low-frequency sound fields can be addressed efficiently through acoustic impedance matching. Basically, the diaphragm of electroacoustic transducers are used as refracting surface that controls the reaction of the boundaries in any surroundi ...

2012

The LHC Transverse Coupled-Bunch Instability

Nicolas Frank Mounet

In this thesis, the problem of the transverse coupled-bunch instabilities created by the Large Hadron Collider (LHC) beam-coupling impedance, that can possibly limit the machine operation, is addressed thanks to several new theories and tools. A rather com ...

EPFL2012

Tunable Electroacoustic Resonators through Active Impedance Control of Loudspeakers

Romain Boulandet

The current trend for multipurpose rooms requires enhanced acoustic treatments capable to meet ever more demanding specifications in terms of performance, compactness and versatility. The reason is the variety of activities to be hosted and the correspondi ...

EPFL2012

Electroacoustic absorbers I: bridging a gap between active acoustic feedback control and shunt loudspeakers

Hervé Lissek, Romain Christophe Rémy Fleury, Romain Boulandet

Variable acoustic properties can be obtained at the diaphragm of an electroacoustic transducer, with the help of very basic control strategies, among which is the simple electrical shunting of the transducer. These shunt techniques are compared to active a ...

2011

Acoustic impedance synthesis at the diaphragm of moving coil loudspeakers using output feedback control

Hervé Lissek, Romain Boulandet

This paper discusses a time-domain technique for synthesizing acoustic impedance at the diaphragm of a loudspeaker using a proportional-plus-derivative output feedback. The dynamics of electroacoustic transducers such as moving-coil loudspeakers can be rea ...

2011

Design of switching amplifier used in negative impedance dispoal for the active control of transducer's acoustic impedance

Hervé Lissek, Romain Boulandet, Pavel Mokry

We present a concept of "active material" with variable acoustic properties, being constituted of an electroacoustic transducer which acoustic impedance can be changed by an active mean. Among the different ways to obtain variable acoustic properties on an ...

2009

Source coding in sensor networks

Robert Konsbruck

Wireless sensor networks have emerged as versatile tools to monitor the evolution of physical fields over large areas by means of self-powered and low-cost sensing devices. Although their development was originally motivated by military applications, they ...

EPFL2009

From the electrical shunting of a loudspeaker to active impedance control

Hervé Lissek, Florian Sandoz

Variable acoustic properties can be obtained on an electroacoustic transducer’s voicing face by very basic control strategies, among which are the shunting of the loudspeaker (shortcut, variable electric load, or negative resistance disposals). It is prove ...

2008

Factoring end-user expectations into the sound design process of computer keyboards

Hervé Lissek, Romain Boulandet

The poor acoustic comfort of usual commercial products is often perceived as annoying. Today, more and more companies have realized that sound can be an important component of product attributes and image. They are interested in having acoustic guidelines ...

2008