1,721,015 research outputs found
The influence of base structure on acoustic performance enhancement through additonal layers
No full textIn the field of noise control engineering, multilayer systems are widely utilised to mitigate noise radiation and improve sound insulation. The effectiveness of additional layers in enhancing acoustic performance significantly relies on the characteristics of the underlying base structure. In fact, evaluating the acoustic efficacy of lining systems in building construction requires standardised heavyweight and lightweight elements as base structures. This study aims to conduct a comprehensive analysis of the relationship between the characteristics of the base structure and the design of multilayer systems as a mitigation strategy. Through parametric analysis of a simulated dataset, this study endeavours to provide valuable insights for accurately evaluating global acoustic performance and developing tools handy in designing optimal multilayer system configurations for effective noise control in building constructions. This paper presents preliminary results aimed at identifying critical parameters for predicting the sound insulation improvement of lining systems
The use of façade sun shading systems for the reduction of indoor and outdoor sound pressure levels
No full textExternal shading devices are widely used in recent buildings because they reduce the greenhouse effect due to the solar irradiation through transparent surfaces and the glare effects in interiors. The acoustic effects of these devices have not been well investigated in the literature. In this article, we use a bi-dimensional pressure acoustics finite element model of a shading device attached to a building facade, in frequency domain, to analyse the effects both in the indoor and in the outdoor environments. The finite element model was validated with experimental measurements carried out in a semi-anechoic chamber and then extended to an urban scale to evaluate the effect in the reduction of outdoor noise due to traffic. To improve the acoustic effect of the shading device, a sound absorbing material was added to the bottom side of each louvre. Results of the simulations show that external shading devices tend to increase the sound pressure level over the building facade, while the introduction of the sound absorbing material behind each louvre reduces this problem. The dependencies of the sound pressure level reduction to the geometrical factors of the shading device were investigated by means of the finite element model. The installation of louvres on a building facade can affect also the sound pressure level over a facade of a building placed 20 m away, across a road. In this article, both the effect over the facade of the opposite building and the effect over the urban area between the two buildings are analysed
Building materials: Influence of physical, mechanical and acoustic properties in sound prediction models
No full textSeveral models to compute the sound reduction index of a building partition, based on different approaches, can be found in the literature. Building construction involves a great variety of materials, and regardless of the chosen sound transmission simulation prediction approach, their elastic and physical properties, which are necessary as input data, have a strong influence on the accuracy of the predicted results. In this article, the influence of such properties is investigated, by means of a prediction model based on the method proposed by the recently updated standard EN ISO 12354. Moreover, the reliability of different prediction models and the consistency of their results have been tested, by simulating several building partitions made of various materials, both homogeneous and non-homogeneous
Prove interlaboratorio per la determinazione dei valori di ripetibilità e riproducibilità nella misura del potere fonoisolante di pareti
No full textDetermination of the structural response of lightweight structures by means of sound pressure measurements
No full textFrom the dynamic response of a vibrating structure, it is possible to determine trustworthy insights about the acoustic and mechanical properties of that specific element. The structural wavenumber, propagating along a certain direction, can be determined from the dynamic response of the element, measured along a line of equally spaced points. Moreover, the radiation efficiency of the structure, for example, can be computed from the complex vibration velocity, measured over a grid of points on the surface of the element. Measurements of the vibrational filed are commonly performed by using accelerometers attached to the surface of the vibrating object. By using miniature transducers, it is possible to investigate a wide range of structures, even though non-contact transducers are sometime preferred, in order to avoid any small influence of added masses on the dynamic response of very lightweight elements. Optical methods have been widely used to overcome such issue, although they require very expensive equipment, such as a laser Doppler vibrometer. Near-field acoustic holography represents an alternative contactless approach, which allows the reconstruction of the structural dynamic response from the sound pressure measured with an array of microphones. In this study the possibility to accurately determine the structural response of a lightweight structure by measuring acoustic pressure in the vicinity of the vibrating surface has been investigated. The reliability of the results has been determined by comparing the structural response reconstructed from sound pressure measurement to the response directly measured by using accelerometers. Furthermore, the elastic properties of the structures, derived from their dynamic response, have also been compared
Experimental investigation of sound radiation: influence of structure-borne transmission
No full textDouble-leaf partitions constituted by plasterboard panels installed on steel studs creating an air-cavity or filled with sound absorbing material are widely employed in building constructions. It is well known that, due to the presence of the studs, the sound insulation of these structures is significantly lower than the theoretical value computed by neglecting mechanical connections. However, the influence of studs in the case of mechanical excitation and structure-borne sound transmission has not been thoroughly investigated. This study experimentally analyses the influence of studs on sound radiation, by comparing the radiation efficiency of a single plasterboard plate and a double-leaf partition. The vibration velocity was measured on the investigated structures, excited by an electro-dynamic shaker. The results highlight the importance of the studs' elasticity. At higher frequencies, lower vibrational levels are measured on the radiating panel of the double-leaf system. However, at the lower frequencies, the double-leaf partition exhibited a higher radiation efficiency, probably due to the modal behaviour of the system
Acoustic measurements in opera houses: comparison between different techniques and equipment
No full textA standardized measurement technique for the collection of a complete objective description of an opera house acoustics is proposed. The results obtained from measurements made in three different halls were compared between different hardware and software tools and between different measurement methods as well as between different positions in the halls, with and without the presence of musicians and audience. The only effective differences were found regarding the recording techniques, as the monaural measurements give appreciably different results from the average of left and right channel of binaural measurements. Slightly different results were also found between true impulsive sources and omni-directional loudspeakers
Using near-field acoustic measurements to characterise mechanical and acoustic properties of lightweight building structures
No full textThe evaluation of the vibrational field on a certain surface has a great importance in noise control engineering applications. It can be helpful, both for noise reduction purposes, and diagnostic purposes, in product optimisation, or in order to characterise the mechanical properties of the vibrating structure. Accelerometers are still the most used sensors to measure vibration. However, contactless transducers, such as scanning laser doppler vibrometers (LDV), have been widely used recently, presenting several advantages. Near-field acoustic holography may represent a valid alternative to LDV, in order to reconstruct the vibrational field on a surface from sound pressure measurements performed with an array of microphones. This paper presents the preliminary results, of a ongoing project regarding the use of near-field acoustic holography to characterise the elastic and acoustic properties of a lightweight building structure. The used test rig allows to scan the sound pressure over the vibrating surface on a grid of points, using an array of microphones. The panel's dynamic response was used to evaluate its elastic properties. The reliability of this experimental approach was assessed by comparing the results with the ones obtained using miniature accelerometers. These elastic properties were finally used as input data to model sound transmission through the plywood panel using the transfer matrix method, investigating the accuracy by comparing the numerical results with the experimental sound insulation
The acoustics and restoration of ''Salone Pedrotti'' in Pesaro
No full textThis paper deals with the experimental results gathered in order to define the acoustic
characteristics of the “Salone Pedrotti” in Pesaro, before its restoration.
The hall is rectangular, with about 800 divided seats between the stalls and the two galleries.
It is one of the few examples of shoe-box halls in Italy.
To evaluate the acoustic characteristics of the hall, the main acoustic parameters in use today
were measured at various points.
The results of the measurements revealed values of the acoustic parameters which were very
close to those considered optimal for halls of this size and use. From the results of the
measurements, the great importance of the ceiling and the link between the top of the stage and
the loft, comes out. The wall separating these two parts is formed by a light structure made of
plaster and straw, unlike the heavy walls usually imposed by fire protection regulations. The
ceiling is therefore not only a passive element of acoustic reflection, but also an active element,
capable of radiating acoustic energy coming from the top of the stage.
In view of the required restoration of the ceiling, further studies are being carried out in
order to better understand the acoustic function of this element of the hall and to be able to give
valuable advice regarding the necessary interventions to safeguard this acoustic function and at
the same time strengthen the structure
FE-based approach to compute the sound transmission loss of building partitions
No full textThis paper investigates a numerical approach to compute sound transmission loss of building partitions and other structures. This method requires that, a unit cell, a small portion of the considered partition, is modelled by using the Finite Element Method (FEM), and coupled with semi-infinite fluid domains on both sides. On the sending side, the structure is excited by an acoustic plane wave. Bloch-Floquet periodic boundary conditions are applied in order to consider the structure of infinite extent. The infinite sound transmission coefficient of the considered partition is computed from the sound field variables obtained from the FE simulation. To increase the accuracy of the results below the critical frequency, the finite-size radiation impedance can be considered. The transmission loss computed with this approach is comparable with the results obtained by means of the transfer matrix method (TMM). In this study the validation of the results, obtained with the FE approach, and an assement of their accuracy were achieved by comparing them with the sound transmission loss computed using the TMM. Moreover, the influence on the results of practical aspects of the implementation of the model, such as dimension of the unit cell, the number of elements in the perfectly matched layer domains, the extension of the fluid domains and the size of the mesh were investigated by means of a parametric analysis
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