Design and modeling of a periodic single-phase sandwich panel for acoustic insulation applications

Sandwich and composite panels are widely adopted in acoustic applications due to their sound insulation properties that overcome mass-law-based partitions in medium–high frequency regions. A key aspect in the design procedure of acoustic panels is the control of the resonance-dominated region of the sound transmission loss (STL) curve. Within that frequency range, such systems usually show acoustic weakness and poor insulation performances with respect to standard single-layer solutions. In the present contribution, we want to highlight an innovative approach to the sandwich partition concept. A novel single-phase sandwich panel is realized by adopting a periodic repetition of a properly designed unit cell. The resulting internal truss structure is self-sustained, and its mechanical stiffness can be tuned to maximize the STL in the resonance-dominated region. A set of parametric analyses is reported to show how the topology of the unit cell affects the noise reduction properties of the panel. Experimental validation is performed on a nylon 3D-printed prototype. The proposed panel is then integrated with some locally resonant elements that can be adopted to further improve the low-frequency STL of the solution. Industrial and production considerations are also taken into account during the design process to make the solution industrially valid with a circular economy focus

PPARα transcriptionally induces AhR expression in Caco-2, but represses AhR pro-inflammatory effects

International audienceIn this work we demonstrate that Caco-2 cell treatment with WY-14643 (a potent PPARa agonist) causes an increase in AhR expression. Luciferase assays and directed mutagenesis experiments showed that induction mainly occurred at transcriptional level and involved a PPRE site located within the AhR promoter. These results were further confirmed by the use of PPARa knockout mice in which AhR induction by WY14643 was abrogated. In addition to CYP1 regulation, AhR has been described as being involved in inflammation , so we also studied the effect of AhR regulation by PPARa on the expression of some inflammation target genes. 3-Methylcho-lanthrene (a potent AhR agonist) increased the expression (mRNA) of the major inflammatory targets IL-1b and MMP9. WY-14643 co-treatment abrogated the 3-methylcholanthrene pro-inflammatory effect. Hence the anti-inflammatory effect of PPARa overrides the pro-inflammatory effect of AhR

Interaction with a High- versus Low-Competence Influence Source in Inductive Reasoning

International audienceLiterature on inductive reasoning shows that when testing hypotheses, people are biased toward the use of confirmatory strategies (P. C. Wason, 1960). In the present article, the authors presented 2 studies showing how people use confirmation and disconfirmation strategies during actual interaction in problem solving. Study I showed that participants were able to learn to use disconfirmation when confronted with a low-competence, nonthreatening partner. When the partner was high in competence (thereby threatening the participant's competence), participants used confirmation, even when the partner used disconfirmation. In Study 2, the authors aimed at generalizing the aforementioned results by exploring the hypothesis that disconfirmation stems from the possibility of diverging from norms. Participants who were confronted with the violation of a conversational norm used a high proportion of disconfirmation, whatever the source of influence. When there was no violation but there was a low-competence partner, the proportion of disconfirmation was high; when there was no violation but there was a high-competence partner, the proportion of disconfirmation was low. The authors discussed the interpersonal functions of confirmation and disconfirmation

From mechanics to acoustics: Critical assessment of a robust metamaterial for acoustic insulation application

The increasing popularity of sandwich and composite double panel structures stems from their better sound insulation properties over a wide frequency range with respect to their single panel counterparts. However, in the design of such multi-layer panels particular attention must be paid to the resonance dominated region of the Sound Transmission Loss (STL), where the Mass-Spring-Mass resonance causes a frequency region of poor acoustic performance. In the present contribution, a metamaterial unit cell endowed with an ultra-wide band gap is integrated with faceplates to create a novel acoustic insulation sandwich panel. The panel is realized with a single material and with a properly designed mechanical stiffness that does not affect results in terms of acoustic wave attenuation over a wide frequency range, making at the same time the internal core self-sustained. The STL of the panel is numerically evaluated through a plane wave tube model. The solid-air interaction in terms of resonance frequencies is critically assessed and accurately described by the proposed lumped-parameter model. The model represents a simple tool to predict and optimize the behaviour of the panel in the resonance dominated region of the STL. The acoustic performances of the panel are validated through an experimental campaign on a Nylon prototype, which is 3D printed through Selective Laser Sintering technique

DEVICE FOR REDUCING FAN-GENERATED NOISE

The present invention relates to a device (10) for reducing fan-generated noise, comprising: a plurality of grid elements (201, 902) identifying a main development plane, and empty portions (202) delimited by the grid elements (201, 902) and configured for the passage of an airflow through the device (10), wherein each of the grid elements (201, 902) comprises a respective inner cavity (501, 903) delimited by side walls, the side walls defining at least one tube opening (401) facing a respective one of the empty portions (202) and substantially orthogonal to the main development plane, the inner cavity (501, 903) being acoustic resonant for reducing the fan-generated noise. The device (10) has a substantially circular overall shape (101, 102, 103, 104) having a substantially circular outer edge (203), first grid elements (201) of the grid elements (201, 902) having their main direction of development aligned to the outer edge (203), the first grid elements (201) being tangentially arranged and aligned with each other on concentric circumferences in the substantially circular overall shape (101, 102, 103, 104)

ACOUSTIC ATTENUATION DEVICE FOR PROPAGATED SOUND THROUGH SURFACES

The present invention relates to un acoustic attenuation device (100) for propagated sound through surfaces. The acoustic attenuation device is of the layered type and comprises an innermost connection layer (101), adapted to associate the acoustic attenuation device (100) with at least one surface. The acoustic attenuation device (100) further comprises an intermediate layer (102), comprising a plurality of attenuation modules (103), each of which comprises at least one movable element (201) defined by at least one first opening (202), the at least one movable element (201) being adapted to vibrate relative to the at least one first opening (202) in a resonant manner when hit by the propagated sound, to attenuate the propagated sound by mechanical dissipation. The acoustic attenuation device (100) further comprises an outermost layer (104), comprising at least one closure surface (105) defining at least one cavity (301) facing the movable elements (201) and adapted to encapsulate the movable elements (201) of the attenuation modules (103) of the intermediate layer (102), to further attenuate the propagated sound by sound-absorbing effect