The indoor air quality inside living spaces is a fundamental factor in providing adequate comfort. In order to do this, a minimum air exchange must be ensured. This can be obtained by means of ...natural or mechanical ventilation or using the Controlled Mechanical Ventilation system (CMV). CMV ensures better energy performance, as in the winter period, the warm air that comes out of the building preheats the cold air that enters, and the opposite occurs in the summer period. A possible problem with CMV is the noise of the fans due to the movement of air and to the electric motor rotation. This work presents the results of acoustic measurements performed on an apartment equipped with CMV, operating in a single and simultaneous mode. Acoustic simulations are also presented using raytracing software on three typical apartments. The acoustic simulation carried out using an adequately calibrated 3D model has proved to be a valid support for the study of noise in rooms connected by doors and corridors. By differentiating the fan speed of the CMV, a considerable acoustic comfort improvement was obtained in the bedrooms and in the living room/kitchen. Class I for living rooms and class I or II for bedrooms according to the EN 16798-1 standard were achieved through speed optimization.
The appropriate acoustic insulation project of building façades is of importance for the design of highly comfortable living environments. In some countries, national regulations require maximum ...noise levels inside rooms, or minimum sound insulation limits, to be respected. The acoustic insulation design of a façade is usually performed according to the ISO 12354-3 standard, which presents a calculation method based on the geometry of the room, the shape of the façade, the areas and the acoustic performances of the individual elements. The prescribed limits must be experimentally verified according to methods derived from international standards. However, the current versions of such standards do not provide details on how to perform the measurements and the calculation of the sound insulation for corner rooms. An important remark is that, depending on the position of the sound source used for the measurements, different results of the standardized sound insulation are obtained. This article proposes a new method for calculating the façade insulation of corner rooms by introducing the acoustic attenuation due to the diffraction of the corner and the distance of the sound source from the façades, estimated through simulations and experimentally validated.
Equipment, sound sources, operators, microphone placement, calculation techniques, and thermal–humidity measurement conditions all have an impact on the measurement of impulse responses when several ...channels are present. However, the thermal–humidity variable, which is a significant component of these factors impacting the assessment of acoustic characteristics, is commonly overlooked in research. The effects of altering temperature, relative humidity, and air velocity on acoustic parameters are investigated in this paper through experimental activities carried out in an experimental room. The patterns of fluctuation of a range of room acoustic characteristics are examined, data are acquired, and statistical analyses based on R (language and environment for statistical computing and graphics) are generated in order to ascertain the relationship between the variation of acoustic parameters and the variation of thermo-hygrometric parameters. Finally, a statistical analysis reveals relationships between thermal and hygrometric variables and interior acoustic characteristics.
Cross-Laminated Timber (CLT) is a building technology that is becoming increasingly popular due to its sustainable and eco-friendly nature, as well as its availability. Nevertheless, CLT presents ...some challenges, especially in terms of impact noise and airborne sound insulation. For this reason, many studies focus on the vibro-acoustic behavior of CLT building elements, to understand their performance, advantages and limitations. In this paper, a 200 mm CLT floor has been characterized in the laboratory, according to ISO standards, by three noise sources: dodecahedron, standard tapping machine and rubber ball. In order to understand the vibro-acoustic behavior of the CLT floor, measurements through the analysis of sound pressure levels and velocity levels, measured by dedicated sensors, were performed. Analysis was carried out in order to understand what is prescribed by the prediction methods available in the literature and by the simulation software. Then, a specific prediction law for the CLT floor under investigation was derived. Finally, an analysis on sound radiation index is provided to complete the vibro-acoustic study.
Composite panels are being increasingly used in many applications because they can combine several interesting properties, such as high load-bearing capacity, low weight, and excellent thermal ...insulation. Different core materials can be used for composite sandwich panels, like polystyrene, mineral wool, polyurethane, glass wool, or rigid phenolic foam, which is considered the rigid plastic foam with the best fire-proof properties. During the research and development phase, the use of simulation tools is often required for the improvement of the mechanical behavior of the material. The aim of the paper is to characterize some vibro-acoustic parameters of a sandwich material with phenolic open-cell foam core. The sound transmission loss of the structure is calculated based on its flexural behavior, represented through a frequency-dependent “apparent” bending stiffness which is estimated by natural frequency vibration tests on beam specimens. The comparison between sound transmission loss predictions and measurements in sound transmission suites according to ISO 10140-2 is presented and discussed. Finally, the early-stage prediction potentiality of the mathematical model is investigated when only nominal information is available on the constituent layers, showing that particular attention should be paid to the modifications introduced by the manufacturing process.
•A comprehensive vibro-acoustic analysis of a timber floor is provided.•Two new correlation models are found, between vibrations levels.•Frequency trends of the radiation efficiency are ...determined.•Equivalent Young’s moduli are provided for three different noise sources.•Standard models are tested and verified.
In recent years, the use of sustainable construction materials has increased significantly. It is of paramount importance to increase the general knowledge of acoustic behaviour of these materials. This research presents the results of a comprehensive acoustic investigation of a 200 mm timber slab. Excitations using different acoustic sources are performed. The results to this investigation are reported in this paper, focusing on the sound reduction index, impact noise reduction, static and frequency-dependant Young’s modulus, vibration and modal mapping and radiation efficiency. Finally, a correlation between impact noise levels caused by the tapping machine and the rubber ball is provided.
Timber is growing more popular as a construction material nowadays. Indeed, it is sustainable, user-friendly and widely available. However, homeowners of timber buildings still complain of perceived ...indoor noise, specifically upon impact. Thus far, very little research has been conducted into this issue. This paper reports the results of the acoustic measurement campaign, conducted in a laboratory, on 14 different floating floors laid on a 200 mm cross-laminate timber slab. Results clearly demonstrate that neither the literature nor existing standards are applicable, as both refer to bare heavyweight floors (like concrete). Hence, new models for the prediction of noise reduction are proposed and validated using the tapping machine and the rubber ball as impact sources. Proposed models are then compared to literature measurements, confirming their effectiveness and their capability of predict impact noise reduction of a floating floor (concrete screed coupled with resilient layer) laid on a cross laminated timber floor.
•Analytical modelling of floating floor on CLT structures is presented.•Literature and standards models demonstrated to be inapplicable.•New models are proposed and validated.•Achieved mean standard deviation is less than 1 dB.•New references curves are provided for frequency-dependent prediction.
Clay hollow brick walls are still popular in building industry, but the prediction of their sound insulation properties is not straightforward due to their inhomogeneous and anisotropic ...characteristics. In this article, a classic approach has been used to determine the sound transmission coefficient of brick walls, assuming an orthotropic behaviour and deriving the mechanical and dynamic characteristics from datasheet information. Different types of walls with horizontal and vertical mortar joints have been analysed. Experimental measurements of the sound reduction index carried out according to ISO 10140-2 standard have been performed, and the resulting values are compared with the predictions in the proposed model. It was found that the sound reduction index can be fairly predicted in the low-frequency range and it is correctly predicted in the mass law region, whereas in the high-frequency range the inner block structure is responsible for a loss of performance which is difficult to predict with the analytical methods.
The internationally recognized procedure ISO 354:2003 for measuring sound absorption coefficients under diffuse field conditions is now under revision. The main reason for this revision is the ...limited reproducibility of absorption coefficients measured in different laboratories that may have significant implications spanning from room acoustic design to material selection. A network of Italian laboratories have come together to carry out an Inter-Laboratory Test (ILT) to assess and compare the measurement uncertainties resulting from the application of the current version of ISO 354:2003 and of the new ISO/CD 354:2019. After detailing the methodological aspects, the paper presents the results of the measurements, discussing the compliance of the laboratories to the standard requirements and new qualification tests, and, more importantly, providing a quantitative estimation of their effects on measurement uncertainty and accuracy.
Gypsum board walls are widely used in today’s buildings. A possible way to considerably increase the sound insulation performances of such lightweight walls is to apply double-layer gypsum panels ...screwed together. Being the boards separated by a thin air gap, there is no shift of the critical frequency from the single-layer case. Moreover, it is possible to obtain an improvement of the sound insulation performances provided by the additional mass given by the double layer. The thin air layer is, however, responsible for a loss of acoustic performance due to the cavity resonance effect in the frequency range between 800 and 1600 Hz. In this article, the increase in the acoustic insulation achieved through the use of coupled gypsum boards is studied and a modelling technique based on the transfer matrix method is used to simulate the acoustic behaviour of the resulting structure; in particular, the thin air layer between the coupled boards is modelled. The simulations are compared with laboratory measurements carried out according to the international standard series ISO 10140. The transfer matrix approach is found to be suitable to describe the problem, provided that a modified model for the air gap between the boards is applied.
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