DIME - Dept of Mechanical Engineering

Background. The conventional approach to coronary angiography exploits static perspective imaging over multiple cardiac cycles, using a limited number of empirically selected views. This approach entails both lack and redundancy of information and may result in suboptimal visualization of the individual lesion, contributing to diagnostic inaccuracy.

The paper describes the theoretical and numerical analysis of sound attenuation in a parallel-baffle rectangular duct. Insertion losses in a frequency range up to 8000 Hz were predicted by means of a FEM numerical model and by means of analytical models from Sabine and Kurze. The models were then validated in the frequency range from 125 to 8000 Hz by comparing theoretical and numerical results with experimental data obtained in accordance to EN ISO 11691 and EN ISO 7235 standards. The results of the comparison indicate that the behavior of such a dissipative/reactive silencer, with its internal-reflections and energy dissipation phenomena, can be predicted quite well by the FEM model on the whole frequency range. On the contrary, analytical models show little accuracy and such predictions are not always so accurate as design requires; besides, the complexity of the analytical approach tends to limit its application to the common design practice. Overall comparisons suggest that FEM modeling can be an accurate and inexpensive way to predict sound attenuation in parallel-baffle mufflers and fulfill the ever rising needs of proper methods in acoustic design of AC and ventilation plants.

Experimental data on acoustical performances, in particular on sound absorption of several green roof systems were evaluated and discussed. Measurements were performed on samples of three green roof systems, different for maintenance, plant setting and containment criteria, and categorized in extensive green roof (Sample A), semi-intensive green roof (Sample B) and common soil (Sample C). Experimental values of normal incidence acoustic absorption coefficient and acoustic impedance were evaluated for each sample in one-third octave frequency bands from 160 to 1600 Hz by using a standing wave tube. Then, diffusive sound absorption coefficients and normal and diffusive weighted sound absorption coefficients were calculated in the same frequency range. Results show that green roofs provide high sound absorption, mostly if compared with the typical performances of traditional flat roofs. Curves of sound absorption coefficients result strongly dependent on the stratigraphy. Comparison between the different systems performed on the base of weighted sound absorption coefficients shows a better behaviour for the Sample B. Results obtained suggest that green roof technology, in addition to energy and environmental benefits, can contribute to noise control in urban areas by means of high sound absorption performances in relation to the size of the surface area.

Ports and harbors are characterized by several complex operations, especially if compared with other logistic nodes. In these scenarios, noise pollution analysis is complicated due to the presence in the same area of several types of sound sources with different characteristics. Noise from port areas comes not only from ferries, ships and trade but also from industrial and shipyards activities as well as auxiliary services. In this way, noise pollution can produce negative effects both to the natural eco-system and to the urban population.
To assess and manage the environmental port noise, the ENPI CBC Med project MESP (Managing the Environmental Sustainability of Ports for a durable development) addresses the reduction of pollution from port activities through the implementation of a multidiscipli-nary approach, which encompasses technological, regulatory and administrative solutions.
The MESP project, starting from an analysis of the “status quo” of current ports condition both in the Northern and Southern part of the Mediterranean basin, aims to reach the identifi-cation of best practices, methodologies, technologies and procedures adaptable and transfera-ble in different Mediterranean port contexts which will be merged in certification processes for procedures and tools allowing to reach an higher level of sustainability and to decrease the pollution level, reinforcing, at the same time, competences of public-decision makers and local administrators.
Optimizing the noise characterization through environmental acoustical monitoring plans al-lows to identify, by means of sound level measurements and proper acoustic descriptors, the most critical noise zones, to recognize the causes producing them and to acoustically charac-terize sound sources (sound power, spectral characteristics, duration). Only in this way the activation of operative actions for the acoustical comfort improvement of critical areas can be successfully implemented. Therefore, management actions and intervention priorities against noise in port areas can be planned and developed by improving procedures, policies and tools.

Perforated facings used in lined ducts or sound absorbing panels can have various purposes: protecting the porous sound absorbing material from dust or grazing flow, acting as a rigid support for the porous material, or also affecting the behaviour of the "backing" material, modifying this way the acoustical performance of the porous layer. This paper describes the effect of perforated facings on sound absorption characteristics of samples made by polyester fibre, experimentally investigated in accordance with ASTM C384 04 standard by means of two Kundt's tubes with different diameters. The polyester (PET) fibre material had bulk density of 30 kg/m3 and melting point at 260°C. The analysis was performed for a sample thickness equal to 100 mm. The samples were faced by means of different metal plates perforated with circular holes. The holes diameter was equal to 2 mm for all facings, while the percent open area was varied from 4.9% to 30%. The perforated panels were positioned in adherence of the PET fibre material or at a distance of 2, 4, and 6 mm. The different behaviours due to the multiple combinations of percent open area and distance from the sample have been then analyzed and discussed.

Experimental data on acoustical performances, in particular on sound absorption of several green roof systems were evaluated and discussed. Measurements were performed on samples of three green roof systems, different for maintenance, plant setting and containment criteria, and categorized in extensive green roof (Sample A), semi-intensive green roof (Sample B) and common soil (Sample C). Experimental values of normal incidence acoustic absorption coefficient and acoustic impedance were evaluated for each sample in one-third octave frequency bands from 160 to 1600 Hz by using a standing wave tube. Then, diffusive sound absorption coefficients and normal and diffusive weighted sound absorption coefficients were calculated in the same frequency range. Results show that green roofs provide high sound absorption, mostly if compared with the typical performances of traditional flat roofs. Curves of sound absorption coefficients result strongly dependent on the stratigraphy. Comparison between the different systems performed on the base of weighted sound absorption coefficients shows a better behaviour for the Sample B. Results obtained suggest that green roof technology, in addition to energy and environmental benefits, can contribute to noise control in urban areas by means of high sound absorption performances in relation to the size of the surface area.

Experimental data on acoustical performances, in particular on sound absorption of several green roof systems were evaluated and discussed. Measurements were performed on samples of three green roof systems, different for maintenance, plant setting and containment criteria, and categorized in extensive green roof (Sample A), semi-intensive green roof (Sample B) and common soil (Sample C). Experimental values of normal incidence acoustic absorption coefficient and acoustic impedance were evaluated for each sample in one-third octave frequency bands from 160 to 1600 Hz by using a standing wave tube. Then, diffusive sound absorption coefficients and normal and diffusive weighted sound absorption coefficients were calculated in the same frequency range. Results show that green roofs provide high sound absorption, mostly if compared with the typical performances of traditional flat roofs. Curves of sound absorption coefficients result strongly dependent on the stratigraphy. Comparison between the different systems performed on the base of weighted sound absorption coefficients shows a better behaviour for the Sample B. Results obtained suggest that green roof technology, in addition to energy and environmental benefits, can contribute to noise control in urban areas by means of high sound absorption performances in relation to the size of the surface area.