On the influence of the air flow resistivity on the measurement of the dynamic stiffness of underlays for floating floors

The dynamic stiffness of underlays is a required quantity to predict the reduction of impact and airborne noise transmitted through floating floors. The measurement of the dynamic stiffness is standardized in ISO 9052–1 using a floating floor section of 200 mm edge length. If open pore insulating materials are used for the underlay, the air flow and its flow resistivity have a significant impact on the dynamic stiffness. The standard ISO 9052–1 therefore calculates the dynamic stiffness based on three distinct intervals of the flow resistivity. This contribution analyses and discusses the mathematical origin and practical consequences of these three standardized intervals and proposes an improvement for a revision of the standard. The current physical model is expanded to examine if the results, that are gained from the geometrically reduced systems of the standard, can be transferred to room sized systems.

Studi eksperimental terhadap porositas dan hambat alir udara pada komposit penyerap suara

In this paper, we present a comprehensive analytical and experimental investigation for the determination of the air flow resistivity and porosity of sound absorber composite. The ratio of the volume fraction of fiber and polyester resin is 15, 25, 35, 55 and 65 (%).The dimensions of the absorbent composite sample are 29 mm x 20 cm (diameter x thickness). Porosity and Air flow resistivity of composites have been investigated. The results showed that the porosity of the composites increased with increasing amount of fiber due to the interface between fiber and resinless dense. In contrast, the air flow resistivity values are lower with a denser resin and fiber interface.Keywords: Air Flow Resistivity, Fibrous composite, Porosity, Sound Absorber

Studi eksperimental terhadap porositas dan hambat alir udara pada komposit penyerap suara

In this paper, we present a comprehensive analytical and experimental investigation for the determination of the air flow resistivity and porosity of sound absorber composite. The ratio of the volume fraction of fiber and polyester resin is 15, 25, 35, 55 and 65 (%).The dimensions of the absorbent composite sample are 29 mm x 20 cm (diameter x thickness). Porosity and Air flow resistivity of composites have been investigated. The results showed that the porosity of the composites increased with increasing amount of fiber due to the interface between fiber and resinless dense. In contrast, the air flow resistivity values are lower with a denser resin and fiber interface.

Studi eksperimental terhadap porositas dan hambat alir udara pada komposit penyerap suara

In this paper, we present a comprehensive analytical and experimental investigation for the determination of the air flow resistivity and porosity of sound absorber composite. The ratio of the volume fraction of fiber and polyester resin is 15, 25, 35, 55 and 65 (%).The dimensions of the absorbent composite sample are 29 mm x 20 cm (diameter x thickness). Porosity and Air flow resistivity of composites have been investigated. The results showed that the porosity of the composites increased with increasing amount of fiber due to the interface between fiber and resinless dense. In contrast, the air flow resistivity values are lower with a denser resin and fiber interface.

Noise attenuation performance of warp knitted spacer fabrics

The development of functional textile structures is important to improve noise attenuation of human life in automotives, residential and occupational environments. In this research, an attempt has been made to find the suitability of three-dimensional (3D) knitted spacer fabrics for sound absorption. Hence, an experimental and analytical investigation on the sound absorption behavior of warp knitted spacer fabrics was conducted. Due to their porous nature, interconnected pores, bulkier and 3D structure, the spacer fabrics have the ability to attenuate more sound energy than conventional materials. This research examined the acoustic properties of spacer fabrics in relation to material parameters such as thickness, density and surface structure and structural characteristics such as massivity, porosity, tortuosity and air flow resistivity. The sound absorption coefficient of the test samples was measured using the impedance tube method by ASTM E-1050 in the frequency range of 50–6400 Hz. The results showed that the acoustic insulation of spacer fabric improves with their thickness and massivity, reduction in their porosity, tortuous path and high air flow resistance. Advance statistical evaluation and two-way analysis of variance is used to analyze the significance of the combined effect of various factors on air flow resistivity and the noise reduction coefficient. These findings are important requirements for the design of spacer fabrics for noise control in the automobile upholstery, buildings, auditoriums, etc.

Inverse estimation of the Dunn and Davern model coefficients for jute material using the particle swarm optimization method

Today many different natural materials are being effectively used in the acoustics and noise control domain. In this study, the acoustical characterization of three different types of natural jute felt material is performed by an experimental method and by using the Dunn and Davern model, along with an inverse characterization method. There are many empirical models available in the literature which describes the acoustical behavior of specific material accurately, as they are specially developed for that material. In this study, the possibility of using only the air flow resistivity based Delany–Bazley model and the Dunn–Davern model for acoustical performance prediction of jute material is tested. However, these two models do not show good matching with the experimental data throughout the frequency range of interest. Particularly in the low frequency region, the level of mismatch between experimental and model data is high. Therefore the inverse prediction of the coefficients [Formula: see text] in Dunn–Davern model using the particle swarm optimization (PSO) method is conducted, and new coefficients for jute material are found. These new coefficients better predict the acoustical performance of jute felts and reduce the mismatch level in the low-frequency region.

Experimental study of wood acoustic absorption characteristics

The objective of this study was to determine normal impedance on the surface as well as sound absorption coefficients for several wood species from Europe and from the tropical zone. The mathematical models of Miki, Attenborough, and Allard – dealing with acoustic properties of porous materials – have also been compared. The air flow resistivity exhibits a distinct link between fiber dimensions and wood porosity. The highest sound absorption coefficient was found for oak, ash, sapeli, and pine woods at 2 kHz frequency. The Attenborough model provides results closest to laboratory measurements, although it still requires significant improvements. The Miki and Allard models have some drawbacks and should be applied with reservation for the determination of wood acoustic properties.