a review of experimental techniques for nvh analysis on a commercial vehicle

Abstract Noise and vibration of automotive vehicles are an increasingly important issue in the automobile industry, for implications on both environmental noise pollution and comfort perceived by driver and passengers. Since noise and vibration performances affect the overall image of a vehicle, they are now considered important factors in the entire vehicle design process. In this regard, an accurate experimental evaluation of vehicle noise and vibration levels in both stationary conditions and urban driving conditions are often necessary for undertaking a refinement process of vehicle sound quality, satisfying the development targets. This paper provides a review of the main experimental techniques adopted for the measurement and analysis of noise and vibration in a commercial vehicle. In order to monitor sound generation in terms of both air-borne and structure-borne noise, the source, transfer path and receiver have to be investigated by noise measurement. For this purpose, different techniques can be employed. Some of them make use of instrumentation (i.e. condenser microphone, sound level meter, sound intensity probe, acoustic holography) which requires particular measurement environments, as it ensures sufficient measuring accuracy only in free field or anechoic conditions. On the contrary, the more innovative pressure-velocity sound intensity method can be used for in-situ tests, without the need to create acoustically treated environments. At the same time, vibration measurements by using proper transducers allow to minimize the structure-borne vibration transmitted from vehicle power plant to chassis and body structure. Experimental modal analysis is another standard tool in vehicle NVH development for determining the dynamic characteristics of a system, and therefore for reducing the risk of failure or excessively high structural vibration or sound pressure levels. Hence, in present work, noise and vibration frequency spectra of experimentally analyzed case studies are given, to illustrate how accurate experimental tests are fundamental for identifying the generation causes of typical noise and vibration problems

Experimental Acoustic Measurements in Far Field and Near Field Conditions: Characterization of a Beauty Engine Cover

Present work focuses on experimental acoustic characterization of an engine beauty cover in far field and near field conditions. Specifically, a comparison between results coming from the two different experimental measurement techniques is presented. Experimental campaign has been carried out on a car engine compartment at different operating conditions, by using on one hand a typical pressure microphone for far field measurements accordingly the related prescribed standards, and on the other hand the more innovative Microflown p-u intensity probe (pressure – particle velocity sensor) for near field measurements. In the latter case, experimental tests have been conducted adopting the Scan & Paint method, based on the acquisition of sound pressure and particle velocity by manually moving the probe across the sound field whilst filming the event with a camera. Differently obtained results have been then analyzed highlighting the peculiarities of each of the two techniques. Finally, evaluating noise emissions with and without cover presence, it has been possible to verify the acoustic performances of the component, identifying a less performing acoustic behavior of the material at some specific frequencies. Hence, future developments could regard the possibility to implement an optimization process through the analysis of different materials and configurations, in order to improve cover acoustic insulation properties at the frequencies of interests

Acoustic optimization of a high-speed train composite sandwich panel based on analytical and experimental Transmission Loss evaluation integrated by FE/Test correlation analysis

Present work purpose is to optimize the acoustic attenuation properties of a composite sandwich panel used for a high-speed train structure, choosing the best panel configuration which allows to improve the performances. Firstly, Nilsson’s analytical formulation for Transmission Loss (TL) evaluation has been implemented and experimentally validated on a typical material used for high-speed railway applications, highlighting the opportunity to use a different material to satisfy the new required design specifications. Different materials and stratifications have been then considered and TL parameter of each configuration have been calculated using Nilsson’s formulation, characterizing acoustic behavior in the frequency domain. Once found the composition which ensures the best compromise between high acoustic insulation and low weight, the panel has been physically realized. Finally, an experimental and a numerical modal analysis have been performed on it. Starting from both FE simulation and impact testing outcomes, a correlation study through the computation of the Modal Assurance Criterion (MAC), has been carried out. A good agreement between numerical and experimental analyses has been found, obtaining a reliable FE model for future improvements

Automotive Materials: An Experimental Investigation of an Engine Bay Acoustic Performances

In this work an extensively experimental analysis aimed to verify the sound insulation properties of the engine bay of a commercial passenger car is carried out, evaluating the possibility to adopt different sound absorbing materials, to be applied under engine cover nylon skin, in the place of commonly used polyurethane foams. Experimental tests were performed on the vehicle at different stationary operating conditions, employing typical pressure microphones for far field measurements, according to the related prescribed standards. A limited number of materials has been initially selected through a preliminary analysis, and then employed for creating different engine cover configurations, which were subsequently tested in real engine operating conditions. For a good understanding of the obtained results, an experimental investigation through an innovative in situ impedance method aimed to assess acoustic properties of each considered material has been also performed. Among all the tested materials, only one able to ensure better acoustic performance at mid and high frequencies with respect to the already existing cover configuration, has been finally identified, after considering other selection criteria such as an adequate high temperature resistance and the most cost-effective solution. Future analyses will regard investigations on the use of additional materials, for solving problem in attenuating engine noise also at low frequencies

Acoustic Optimization of a High-speed Train Composite Sandwich Panel Based on Analytical and Experimental Transmission Loss Evaluation Integrated by FE/Test Correlation Analysis

Abstract Present work purpose is to optimize the acoustic attenuation properties of a composite sandwich panel used for a high-speed train structure, choosing the best panel configuration which allows to improve the performances. Firstly, Nilsson's analytical formulation for Transmission Loss (TL) evaluation has been implemented and experimentally validated on a typical material used for high-speed railway applications, highlighting the opportunity to use a different material to satisfy the new required design specifications. Different materials and stratifications have been then considered and TL parameter of each configuration have been calculated using Nilsson's formulation, characterizing acoustic behavior in the frequency domain. Once found the composition which ensures the best compromise between high acoustic insulation and low weight, the panel has been physically realized. Finally, an experimental and a numerical modal analysis have been performed on it. Starting from both FE simulation and impact testing outcomes, a correlation study through the computation of the Modal Assurance Criterion (MAC), has been carried out. A good agreement between numerical and experimental analyses has been found, obtaining a reliable FE model for future improvements

EXPERIMENTAL ANALYSIS OF INNOVATIVE ACOUSTIC MA-TERIALS FOR ENGINE NOISE CONTROL IN VEHICLES

Due to the continuous evolution of vehicle noise regulations, the automotive industry is increasingly looking for more efficient engine bay design solutions to control noise coming from the engine. To this aim, proper acoustic treatments and covers made of multilayered trimmed panels need to be se-lected. Hence, present study reports the results of an experimental investigation aiming to characterize the acoustic properties of innovative absorbing materials to be used in a new identified engine encap-sulation solution. Both sound absorption and sound insulation properties of several selected materials were measured by using an impedance tube. A sound intensity method, as specified by ISO 15186 standard, was finally utilized to assess the sound insulation performance of prototypes of the acous-tically-treated component. In the paper, the acoustic performances of the tested materials are com-pared with reference to standard polyurethane foam based materials, in order to identify more efficient engine encapsulation solutions both in terms of acoustic performance and ease of industrialization

Prescription appropriateness of anti-diabetes drugs in elderly patients hospitalized in a clinical setting: evidence from the REPOSI Register

Diabetes is an increasing global health burden with the highest prevalence (24.0%) observed in elderly people. Older diabetic adults have a greater risk of hospitalization and several geriatric syndromes than older nondiabetic adults. For these conditions, special care is required in prescribing therapies including anti- diabetes drugs. Aim of this study was to evaluate the appropriateness and the adherence to safety recommendations in the prescriptions of glucose-lowering drugs in hospitalized elderly patients with diabetes. Data for this cross-sectional study were obtained from the REgistro POliterapie-Società Italiana Medicina Interna (REPOSI) that collected clinical information on patients aged ≥ 65 years acutely admitted to Italian internal medicine and geriatric non-intensive care units (ICU) from 2010 up to 2019. Prescription appropriateness was assessed according to the 2019 AGS Beers Criteria and anti-diabetes drug data sheets.Among 5349 patients, 1624 (30.3%) had diagnosis of type 2 diabetes. At admission, 37.7% of diabetic patients received treatment with metformin, 37.3% insulin therapy, 16.4% sulfonylureas, and 11.4% glinides. Surprisingly, only 3.1% of diabetic patients were treated with new classes of anti- diabetes drugs. According to prescription criteria, at admission 15.4% of patients treated with metformin and 2.6% with sulfonylureas received inappropriately these treatments. At discharge, the inappropriateness of metformin therapy decreased (10.2%, P < 0.0001). According to Beers criteria, the inappropriate prescriptions of sulfonylureas raised to 29% both at admission and at discharge. This study shows a poor adherence to current guidelines on diabetes management in hospitalized elderly people with a high prevalence of inappropriate use of sulfonylureas according to the Beers criteria

VIBRO-ACOUSTIC ANALYSES IN VEHICLES: EXPERIMENTAL ENGINE NOISE EVALUATION AND PASSIVE CONTROL, SOUND QUALITY ASSESSMENT BY MEANS OF NEURAL NETWORKS ALGORITHM

The NVH (Noise, Vibration & Harshness) comfort of a vehicle represents a key factor in vehicle development process nowadays, since it strongly affects customer judgement and expectations. This in terms of noise levels reduction and pleasantness of sound perception for user comfort, as well as noise pollution to the environment. In the automotive panorama, development cycles are getting tighter, giving NVH engineers less time to deal with typical today’s challenges concerning fuel economy, cost-effective and light-weight design. Increasingly advanced vibro-acoustic experimental and virtual tools can help the vehicle development process from its early stages, favouring synergy with all automotive research activities. The studies presented in this thesis follow the main pillars of a joint effort. In a first analysis, the use of alternative sound absorbing materials for engine noise passive control was explored to then identify the optimal trade off in terms of cost-effective solution and acoustic performance. The subsequent studies, in addition to assess the potential of natural gas vehicles for traffic noise mitigation, rely on the interior acoustic comfort characterization and Neural Networks algorithms-based analysis, carried out through a wide experimental campaign for several diesel engine vehicles, tested in parallel to evaluate emission levels across different driving cycles and conditions

EDUCATION AND THE CARE MAINSTREAMING INTO THE FEMININE BIOGRAPHIES.

This research investigates a varied patchwork of feminine experiences, realized in a socio-educational context. These real-lives are witnessed by the protagonists themselves. In this survey we want to emphasize their story (Selvaggio 2013). The gathered material - between 2013 and 2014 - is in a narrative form according to the biographical method and life stories (Selvaggio 2011; Merrill, West 2012). The aim is to speak for those women who tell us experiences of their real-life, experiences which have a particular meaning by the point of view of the responsibility both for themselves and in the world. Our observation and our reflection focus on the relationship between gender and care (Balbo 2008, 2013). In fact, the common denominator of the various stories narrated by these women is the capability of our protagonists to transcend their reality in a different ways. They make decisions and choices using their care feeling. Their ca pability is declined (Sen 2010) as a daily virtue, an eminently political capability (Nussbaum 2011). In these stories the care concerning others and the self-realization desire are connected and crossed in a modus vivendi that emphasized their own freedom (Gilligan 2014). From the gender point of view, this represents the main aspect of these many real-lives told by our women. The interviewed women, in fact, show us their way to re-appropriate of the care, reinventing it with self-determination and resilience actions