Simon Benacchio

Experimental Demonstration of the Modification of the Resonances of a Simplified Self-Sustained Wind Instrument Through Modal Active Control

This paper reports the experimental results of modifying the resonances of wind instruments using modal active control. Resonances of a simplified bass clarinet without holes (a cylindrical tube coupled to a bass clarinet mouthpiece including a reed) are adjusted either in frequency or in damping in order to modify its playing properties (pitch, strength of the harmonics of the sound, transient behaviour). This is achieved using a control setup consisting of a co-located loudspeaker and microphone linked to a computer with data acquisition capabilities. Software on the computer implements an observer (which contains a model of the system) and a controller. Measuring and adjusting the transfer function between the speaker and microphone of the control setup enables modifications of the input impedance and the radiated sound of the instrument.

Active control and sound synthesis—two different ways to investigate the influence of the modal parameters of a guitar on its sound

The vibrational behavior of musical instruments is usually studied using physical modeling and simulations. Recently, active control has proven its efficiency to experimentally modify the dynamical behavior of musical instruments. This approach could also be used as an experimental tool to systematically study fine physical phenomena. This paper proposes to use modal active control as an alternative to sound simulation to study the complex case of the coupling between classical guitar strings and soundboard. A comparison between modal active control and sound simulation investigates the advantages, the drawbacks, and the limits of these two approaches.

Modal proportional and derivative state active control applied to a simplified string instrument

This study proposes an application of modal active control to musical string instruments. Its aim is to control the modal parameters of the soundboard in order to modify the sound of the instrument. Using both state and derivative state modal control, a method is given, from the modeling of the active structure through to the design of the control system. Issues such as the identification of the structure’s characteristics or the stability of the control system are dealt with for this original control method. Then, this technique is applied to a model of a simplified string instrument soundboard. Time simulations are conducted to study its effect on the instrument vibration. They show that, thanks to soundboard modal active control, it is possible to modify the amplitude of the sound harmonics to change the timbre as well as the sound level of the instrument.

Modal active control applied to simplified string musical instrument

This study aims to control the vibrational eigenmodes of soundboards in order to modify the timbre of string instruments. These structures are wooden plates of complex shape, excited by a string through a bridge. Their modal parameters are first identified using modal analysis algorithms on experimental measurements. Then a digital controller is designed using these parameters and classic active control methods. The effects of this controller are first studied thanks to time simulation. Prior to applying experimentally this controller, an optimization procedure is carried out to determine the quantity, dimensions and positions of sensors and actuators needed for the control. These best possible specifications are obtained according to the controllability, observability and other optimization criteria. Finally, a real time system using the control procedure is tested on a simplified musical instrument. The experiment is conducted on a rectangular spruce plate, clamped at its boundary and excited by means o...

Earplug comfort: From subjective assessment on the field to objective measurement and simulation using augmented artificial heads

For several years, lack of comfort has been pointed out as a major reason of earplug poor efficiency as noise control solution. The great complexity of comfort makes it difficult to predict it in the earplugs design phase. It is rather considered in an empirical way by the manufacturers using trial-and-errors approaches based on subjective assessment over a panel of subjects. Furthermore, because comfort is not quantified, Occupational Health and Safety (OHS) practitioners cannot select earplugs ensuring wearer comfort. To address these issues, a major international research project funded by two OHS institutes (IRSST in Canada and INRS in France) and involving several Universities (in Canada and England) started in 2017. The main objectives are to: (1) improve the understanding of earplugs comfort as perceived by field workers with consideration of all comfort components, (2) develop laboratory tools (augmented experimental and virtual artificial heads) to measure physical design variables related to the auditory, physiological, and functional components of comfort and (3) design a battery of hybrid objective/subjective comfort indices to quantify / measure / predict the different components of comfort. The aim of this presentation will be to present the project and first results.For several years, lack of comfort has been pointed out as a major reason of earplug poor efficiency as noise control solution. The great complexity of comfort makes it difficult to predict it in the earplugs design phase. It is rather considered in an empirical way by the manufacturers using trial-and-errors approaches based on subjective assessment over a panel of subjects. Furthermore, because comfort is not quantified, Occupational Health and Safety (OHS) practitioners cannot select earplugs ensuring wearer comfort. To address these issues, a major international research project funded by two OHS institutes (IRSST in Canada and INRS in France) and involving several Universities (in Canada and England) started in 2017. The main objectives are to: (1) improve the understanding of earplugs comfort as perceived by field workers with consideration of all comfort components, (2) develop laboratory tools (augmented experimental and virtual artificial heads) to measure physical design variables related to the...

Application of a registration method on magnetic resonance images to evaluate the displacement field of a human subject ear canal due to various earplug insertions

Earplugs are a usual way to protect workers subjected to noise exposure. However, the efficiency of these hearing protection devices is often affected by induced discomforts. A factor suspected to impact both acoustical and physiological comfort attributes of earplugs is the deformation they apply on the ear canal walls. As the geometry of both open and occluded ear canal is difficult to obtain, the ear canal deformation due to earplug insertion is not trivial to evaluate. Current medical imaging techniques and image post-processing methods are promising tools to investigate this deformation. In a previous study of the authors, an approach using registration methods on medical images had been proposed to estimate the ear canal displacement field induced by earplug insertion. This approach had been validated in the case of computed tomography scans of a human-like artificial ear occluded by a controlled-shape custom molded earplug. In the present study, this approach is used to evaluate the ear canal displ...

Estimation of the ear canal displacement field due to in-ear device insertion using a registration method on a human-like artificial ear

ABSTRACT Passive and active in‐ear devices (IED) occluding the ear canal are commonly used to (i) protect people from high noise levels (earplugs), (ii) assist people suffering from hearing impairment (hearing aids) or (iii) help people in listening from their sound systems (earbuds). However, the usability and/or efficiency of IEDs can be greatly affected by several discomfort components (physical, acoustical and functional). The mechanical pressure exerted by the IED onto the ear canal walls is greatly suspected to affect the aforementioned comfort components. This physical characteristic is closely related to the displacement field induced by the IED insertion, which has to be known for a better understanding of perceived discomfort. Thus, this paper proposes to validate a method based on medical images to estimate the displacement field of the ear canal walls due to the insertion of an IED. The approach is validated on a human‐like artificial ear with canal geometry deformed using two custom molded IEDs with controlled shapes. These geometries are obtained using computed tomography imaging and the displacement field is computed using a registration method. The errors due to the ear canal segmentation and to the registration steps are small enough to compute a relevant estimation of the expected displacement field. Results show that the amplitude of the displacement and its location into the ear canal can be evaluated with an accuracy of±0.2mm and±0.4mm respectively. Preliminary results on images with a degraded resolution indicate that the proposed approach used to assess the displacement field of the ear canal walls using computed tomography images could be applied on magnetic resonance images, which is a preferred method to image human subject ear canals for future investigations. HIGHLIGHTSThe geometries of an open and occluded artificial outer ear are obtained using CT imaging.The displacement field due to the in‐ear device insertion is estimated using a registration method.The results show that the proposed method is relevant to estimate the ear canal displacement.The method is tested and promising for an application to real human ears using MR imaging.

MRI investigation of the ear canal deformation due to earplugs: A first step toward understanding wearing comfort

The effective protection of earplugs is related to the acoustical attenuation but also to the comfort they provide. Earplugs are acoustic seals used to reduce sound transmission in the ear canal. A perfect contact between ear canal and earplug should ideally avoid acoustic leaks leading to under-protection. Practically, this acoustic seal is achieved applying a greater or lesser deformation on the ear canal walls which depends on the earplug insertion and type. However, a too large deformation can modify the acoustic attenuation and cause physical pain due to mechanical pressure exerted onto ear canal walls leading the wearer to take earplugs off and reducing their protection. This study aims at investigating the ear canal deformation of one human subject due to insertion of various earplugs known for providing different levels of protection and different levels of comfort. The shape of the open and occluded right and left ear canals of the subject is measured using MRI technology. The deformation along t...

Modal active control: A tool to finely adjust the sound of string instruments

Controlling the vibratory properties of musical instruments is an important challenge for musical acousticians, musicians, and instrument makers. The latter try to control these properties modifying mechanical parameters of instruments like their shape or their materials to obtain some expected sound attributes. Musicians also modify the vibratory properties of their instruments to change their sound using mutes, for example. Musical acousticians try to modify these properties because it is an intuitive way to investigate the relationship between the instrument mechanisms and their sound attributes. Inspired by industrial techniques, active control was revealed as a convenient way to answer to the latter goal. Moreover, modal active control is a preferred method for the application to musical instruments since their modal parameters are believed to be good descriptors of their vibratory properties. This study aims at applying modal active control on string instruments. First, the possibilities offered by ...

Combined state and state derivative control applied to musical string instruments

In the following study, the state derivative control is used to complete the usual state control. This combined method allows the control of the vibration amplitude of a structure while ensuring the stability of the feedback loop. Firstly, this article presents the approach which leads to development of a combined control method. Then, simulations are presented in trivial examples to illustrate this method. Finally, an application on simulated simplified soundboard is tested and advantages and difficulties linked to the use of this method on an experimental case are shown.