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Guillaume Haiat
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Implants are routinely employed in orthopaedic and dental surgeries. However, risks of failure, which are difficult to anticipate, are still experienced and may have dramatic consequences. Failures are due to degraded bone remodeling at the bone-implant interface, a multiscale phenomenon which remains poorly understood. Implant stability is a key determinant for the surgical success and is determined by the quantity and biomechanical quality of bone tissue around the implant. The primary stability occurs at the moment of implant surgical insertion within bone tissue, while secondary stability is obtained through osseointegration process, a complex multiscale phenomenon, which strongly depends on primary implant stability. The objective of this presentation is to show how acoustical methods may be used in order to provide a better understanding of the multiscale mechanisms at work at the bone-implant interface. Moreover, we will show how acoustical techniques can be used to retrieve the primary and secondary stability of different implants. The first part of this presentation will describe a methodology combining experimental surgery and a multimodality approach. A dedicated coin-shaped implant model is used and has the advantage of providing reproducible and standardized conditions. We will show how quantitative ultrasound may be used to retrieve information on the evolution of the periprosthetic bone biomechanical properties.The second part of this presentation will focus on the development of non-invasive acoustical methods that may be used to retrieve implants stability. The first set-up uses quantitative ultrasound in order to assess dental implant primary and secondary stability. The second device consists in an impact hammer equipped with a piezoelectric sensor that allows to retrieve the primary stability of implants used in total hip replacement. The validation of both approaches has been done in vitro, in silico and in vivo.


Liu Bilong
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Improvement of sound insulation and absorption performance without increasing weight or thickness has always been the pursuit of the acoustical society. For an acoustical wave in the low frequency range, neither insulation nor absorption is easy to be dealt with by a thin structure, because the noise insulation is restricted by the so-called mass law and the absorption is limited by the reactance of structural input impedance. In both cases, to achieve effective results, the mass of structures need to be handled properly. This lecture outlines the ongoing effort to improve sound insulation and absorption for lightweight structures. Besides, examples on the vibro-acoustic properties of lightweight plates subject to typical excitations are presented, and novel structures designed for low frequency sound absorption are also reported and discussed.

Unique Vibration Phenomena in High-Speed, Lightweight, Compliant Gears

Robert Parker
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Gears have recently been aggressively adopted in large aircraft engines because they improve turbine and fan blade efficiency by better matching the optimal speeds of the associated shafts. The high operating speeds and extreme focus on weight reduction lead to gear vibration behaviors that are distinct from conventional gears. High speeds give high excitation frequencies, and lightweight, thin-walled gears have lower natural frequencies. This combination triggers resonance, gyroscopic effects, nonlinearity, vibration of the gears as elastically compliant bodies, and parametric instability. These behaviors are driving development of new models and analysis tools different than what is typical for conventional gears. This presentation will start with industrial examples motivating the work. Next, we describe modeling and analysis of gear vibration using analytical and finite element/contact mechanics methods, with special attention to planetary gears because they are the de facto standard in aerospace applications and because of their interesting dynamics arising from cyclic symmetry. These models, and their experimental validations, will be used to illustrate and explain, without emphasis on mathematical details, the unique vibration behaviors that occur and how the analytical/computational findings have powerful practical implications.


Meghan Clayard
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One of the most important things we do every day is understand spoken language. Identifying spoken words requires the rapid integration of multiple acoustic-phonetic cues in the richly multi-dimensional and transient speech signal. Every meaningful difference in sounds (e.g. the difference between the sounds at the beginning of 'peach' and 'beach') is signalled by multiple acoustic-phonetic cues (e.g. spectral and temporal differences) and often a single cue is not enough for unambiguous perception. Furthermore, the speech signal is notoriously variable and this variability stems from many sources including the talker (e.g. differences in vocal tract size, differences in dialect) and the context (e.g. the immediately following sound, speaking style). This variability and multidimensionality in the signal are part of the central challenge that human speech perception must solve and compared to automatic systems, humans are better able to deal with the variability in particular. This talk will present an overview of challenges related to multidimensionality and variability in spoken word recognition, including sources of variability, and what is known about the solutions, including the role of plasticity. It will also introduce some recent work in my lab investigating differences between individual talkers and listeners.


Raymond Panneton
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Porous materials everywhere in the Universe! At the Planck length scale (10e-33 cm), physicists describe space as a quantum foam. At the cosmic scale (> 10e26 cm), galaxies are distributed according to the structure of a cosmic foam. Closer to the human scale, natural porous media are formed (honeycomb, soil, rock, bone). This omnipresence and the remarkable properties of these media have long fascinated the engineers who have inspired them to create porous materials adapted to different applications of mechanical engineering: sound absorption and insulation, cooling of electronic components, implants and substitute bones, light structures, absorption of impacts, porous electrodes for fuel cells, filtration and purification of water. After an introduction of the porous media at these different scales, this presentation gives an overview of the porous materials used in noise control. This overview presents conventional and unconventional porous materials. Man manufactures conventional porous materials based on conventional chemical and physical processes and the mimicry of natural porous media. However, it seems that these materials have reached the physical limits of sound absorption and sound insulation. Moreover, their use becomes an important issue in terms of sustainable development. To obtain acoustic properties that go beyond those of conventional materials, and materials more in line with sustainable development, man must intervene by structuring the material and choosing materials safer for the environment. Metamaterials and materials designed using an ascending or a multiscale approach belong to the family of unconventional materials. Similarly, materials based on natural fibers and recycled materials belong to this family. The presentation mainly focuses on this family of materials and the underlying design methods, while presenting examples of applications and comparisons to conventional materials. In parallel, what makes a porous material a good acoustic absorber will be discussed and analyzed.

When Your Life and Ears Depend Upon Hearing Protection: The Conundrum of Auditory Situation Awareness and Attenuation

John Casali
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Prevention of noise-induced hearing loss via hearing protection devices (HPDs), together with con-comitant preservation of one's auditory situation awareness (ASA) and vigilance to the surrounding acoustic environment, is critical. Examples include construction workers who wear electronic ear-muffs but must hear backup alarms, emergency vehicle drivers who need hearing protection from the vehicle's siren but must also hear car horns and communications, and military personnel who wear gunfire-noise-protective headsets but must hear certain signals and speech. This paper re-views several ASA experiments on "augmented" HPDs, which rely on either passive (i.e., dynamic acoustic "valves" and filter) or active (i.e., battery-powered electronic) technologies, that are in-tended to provide "pass-through" hearing capability with concomitant hearing protection. Over the past decade, several in-field and in-lab experiments at Virginia Tech have demonstrated that certain augmented HPDs and Tactical-Communications-and-Protective-Systems (TCAPS) in fact do not provide natural hearing or "transparency," and have deleterious effects on ASA. Experimental stimuli have included vehicular warning alarms, military-relevant signals and other signatures of broadband, low-frequency, and high-frequency content. Measures of ASA performance have in-cluded: hearing threshold at detection, accuracy and response time in recognizing/identifying and localizing signals, and intelligibility of communications. Based on these experiments, an objective, repeatable test battery was developed for evaluating HPD and TCAPS effects on the ASA tasks of: Detection, Recognition/Identification, Localization (azimuth and frontal elevation), and COMmu-nication, known as "DRILCOM." Example results from the ASA testing using various signals are covered. Also, the interaction effects of HPD attenuation with the low-frequency interaural time difference (ITD) cues and high-frequency interaural level difference (ILD) cues that are so critical to localization are covered. It is postulated that standardized ASA testing of augmented HPDs and TCAPS, in similar fashion to commonplace and standardized attenuation testing, should be done before devices are deployed on personnel in dangerous environments.

NOTE: This work received the "Safe in Sound Award for Innovation in Hearing Conservation," awarded by the National Institute for Occupational Safety and Health (NIOSH) in February, 2016. See: http://www.safeinsound.us/winners.html

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