Sound Insulation Properties Research Articles

Non-Wovens as Sound Reducers

Abstract Within the present study, the effect of hemp (40 wt%) and polyactide (60 wt%), non-woven surface density, thickness and number of fibre web layers on the sound absorption coefficient and the sound transmission loss in the frequency range from 50 to 5000 Hz is analysed. The sound insulation properties of the experimental samples have been determined, compared to the ones in practical use, and the possible use of material has been defined. Non-woven materials are ideally suited for use in acoustic insulation products because the arrangement of fibres produces a porous material structure, which leads to a greater interaction between sound waves and fibre structure. Of all the tested samples (A, B and D), the non-woven variant B exceeded the surface density of sample A by 1.22 times and 1.15 times that of sample D. By placing non-wovens one above the other in 2 layers, it is possible to increase the absorption coefficient of the material, which depending on the frequency corresponds to C, D, and E sound absorption classes. Sample A demonstrates the best sound absorption of all the three samples in the frequency range from 250 to 2000 Hz. In the test frequency range from 50 to 5000 Hz, the sound transmission loss varies from 0.76 (Sample D at 63 Hz) to 3.90 (Sample B at 5000 Hz).

Investigation of sound absorption properties of nonwoven webs produced from chicken feather fibers

As a consequence of modern life and technology, noise causes many negative side effects, especially with regard to health. Today, the presence of acoustic problems in transport vehicles such as airplanes, cars and train wagons has become one of the major problems of modern life. Many methods and materials have been developed to provide acoustic comfort in indoor spaces. One of them is the development and application of sound-absorbing materials. Nonwoven webs, which are considered to be the most ideal materials for sound insulation, have micron-sized pores as well as large surface areas. Among these materials, materials with double-layered porosity have greater effect. In recent years, researchers are increasingly turning to the development of sound-absorbing materials from production waste and natural materials that are easily decomposed in the environment. In this study, the sound-absorbing properties of nonwoven webs produced from chicken feather fibers, a by-product in chicken production and a significant amount of waste, were investigated. For this purpose, nonwoven web samples with different parameters were produced by using different binding materials by using thermal bonding method. The sound absorption coefficient and sound transmission loss values of the samples were measured and evaluated. As a result of the analyses, the influence parameters such as thickness, bulk density and porosity on the sound insulation properties of the produced samples was revealed. The assumptions concerning the mechanism of sound insulation of nonwoven webs produced from chicken feather fibers are detailed. Studies have shown that nonwoven webs from chicken feather fibers can be used as soundproof materials because of their good sound-absorbing properties.

Driving-point mobility and sound insulation of structured sheet metal

In lightweight construction, the stiffness of plane sheet metal can be increased by the modification of the sheet metal with structures. The present study aims to determine the sound insulation and excitation properties of such structured metal sheets and the parameters which characterize them. The bidirectional structure of the investigated steel sheets is derived from equilateral hexagons with a bulge, arranged in a honeycomb manner. The acoustic properties of these metal sheets are examined in terms of the driving-point mobility and the sound transmission loss by using the finite element method (up to 16 kHz) as well as laboratory experiments (up to 12.5 kHz).The study shows that the resulting driving-point mobility depends on frequency as well as on structure size. Additionally, it was found that the location of excitation has a notable impact on the resulting mobility spectra. The sound reduction index of the structured sheet metals is similar to that of a plane reference plate for low frequencies up to 4 kHz. In a range of medium frequencies between approximately 5 kHz and 12.5 kHz, the sound reduction index of the structured plates is clearly below that of the reference plate.

Vibroacoustic behavior of orthotropic aerospace composite structure in the subsonic flow considering the Third order Shear Deformation Theory

An analytical model is performed across the aerospace composite structure to interpret acoustic transmission of the infinitely long doubly curved shell considering the effect of mean flow with the aid of Higher-order Shear Deformation Theory (HSDT). Accordingly, the displacements are extended up to cubic order of thickness coordinate based on Third-order Shear Deformation Theory (TSDT) known as HSDT including no effect of shear correction factor. Consequently, in order to present the Sound Transmission Loss (STL) of the present model, the excitation of the structure with an oblique plane sound wave is set in order. However, the acoustic transmission is performed by incorporating the both of shell equations and acoustic wave equations, simultaneously. In the next step, the accuracy as well as the reliability of the present model is provided by comparing the achieved results with those available in literature. Moreover, the present results illustrate the importance of investigating TSDT due to clarifying the more precise outcomes. Finally, the importance of the present model is cleared as a result of improving the mechanical and sound insulation properties particularly in low frequency zone by illustrating the STL comparison between the current structure and those structures without any curvature.

Bi-layer plate-type acoustic metamaterials with Willis coupling

Dynamic effective negative parameters are principal to the representation of the physical properties of metamaterials. In this paper, a bi-layer plate-type unit was proposed with both a negative mass density and a negative bulk modulus; moreover, through analysis of these bi-layer structures, some important problems about acoustic metamaterials were studied. First, dynamic effective mass densities and the bulk modulus of the bi-layer plate-type acoustic structure were clarified through both the direct and the retrieval methods, and, in addition, the intrinsic relationship between the sound transmission (absorption) characteristics and the effective parameters was analyzed. Furthermore, the properties of dynamic effective parameters for an asymmetric bi-layer acoustic structure were further considered through an analysis of experimental data, and the modified effective parameters were then obtained through consideration of the Willis coupling in the asymmetric passive system. In addition, by taking both the clamped and the periodic boundary conditions into consideration in the bi-layer plate-type acoustic system, new perspectives were presented for study on the effective parameters and sound insulation properties in the range below the cut-off frequency. The special acoustic properties established by these effective parameters could enrich our knowledge and provide guidance for the design and installation of acoustic metamaterial structures in future sound engineering practice.

Acoustic perfect absorption and broadband insulation achieved by double-zero metamaterials

We report the mechanism for simultaneous realization of acoustic perfect absorption (PA) and broadband insulation (BI) in the acoustic free field by a layered acoustic metamaterial (LAM). The proposed LAM comprises two critically coupled membrane-type acoustic metamaterials sandwiching a porous material layer. Both theoretical and experimental results verify that the proposed LAM sample can achieve nearly PA (98.4% in experiments) at 312 Hz with a thickness of 15 mm (1/73 of wavelength) and BI in the frequency range of 200–1000 Hz with an areal density of 2.2 kg/m2. In addition, the real parts of both the effective dynamic density and bulk modulus reach zero precisely at the critical frequency of 312 Hz, arising from the monopolar eigenmode of LAM. Our work advances the concept of synthetic design of sound absorption and insulation properties of multi-impedance-coupled acoustic systems and promotes membrane-type acoustic metamaterials to more practical engineering applications.

Sound Insulation Property Study on Nylon 66 Scrim Reinforced PVF Laminated Membranes and their Composite Sound Proof Structure

In this paper, we investigated the sound insulation property of nylon 66 scrim reinforced PVF laminated membranes and their corresponding composite structures with glass fiber felt and carbon fiber board. Sound transmission loss (STL) was measured by standing wave tube method. The results show that, with the decrease of nylon 66 gridlines spacing, STL of nylon 66 scrim reinforced PVF laminated membranes was improved. The sound insulation performance of laminated membranes with gridlines spacing of 3mm is the best, whose STL was up to 10dB at 6.3 kHz. Besides, STL was improved effectively as air layers were embedded into the composite sound proof construction consist of laminated membrane, glass fiber felt and carbon fiber board.

Sound and thermal insulation properties of flax/low melt PET needle punched nonwovens

ABSTRACTNoise pollution is an ever increasing problem in the world because of the industrial revolution. Recently, researchers have begun investigating natural fiber composites as potential materials for the manufacture of sound absorption structures. In this work, flax/low melting point polyester needle punched nonwoven fabrics were manufactured and characterized for sound and thermal insulation applications. Nonwovens were developed by blending flax fibers with low melt PET at three blend ratios (10%, 20%, and 30%) with 7 mm and 10 mm needle penetration depth. The test results showed that there was a decrease in thermal resistance value with increase in low melt PET % and needle penetration depth. The developed nonwovens had better sound insulation value at medium and high frequency. There was no significant change in sound insulation value with increase in low melt PET %.

Manufacturing and properties of ultra-low density fiberboards with an unsaturated polyester resin by a dry process

Although ultra-low density fiberboards (ULDFs) have good sound and thermal insulation performance, formaldehyde emission in the manufacturing process and in the subsequent use of the products limits their field of application. The objective of this study was to employ an unsaturated polyester resin (UPR) in the manufacturing of the boards as a substitute of formaldehyde-based adhesives in order to develop environment-friendly ULDFs. The effects of UPR dosage, fiber treatment agent, press time and fiber consumption on the properties of fiberboards were studied. Sound absorption and thermal conductivity were also measured to ensure sound and thermal insulation properties of the fiberboards. Board density, modulus of rupture and thickness swelling in 2 h were 320 kg/m3, 4.14 MPa and 3.75%, respectively, under optimal conditions such as 12% UPR dosage, 1% fiber treatment agent, 400 g fiber consumption and 210 s press time. Noise reduction coefficient and thermal conductivity of the boards were found within a range of 0.68–0.58 and 0.038–0.048 W/(m K), respectively, while the density of boards ranged from 150 to 400 kg/m3. Therefore, sound absorption property of the fiberboards developed in this study satisfies the requirement of high-efficiency sound absorption materials, which is close to the value (0.67) of ULDF having a density of 56.3 kg/m3 obtained by a wet process. Thermal insulation property of boards was close to that of commonly used insulation materials such as rock wool [0.036 W/(m K)] and glass fiber [0.045 W/(m K)]. In conclusion, fiberboards can be used for non-structural furniture materials, sound and thermal insulation materials in buildings because of their environmental friendliness, good mechanical properties, and excellent sound and thermal insulation properties.

Sound insulation properties of rubberized lightweight aggregate concrete

This study aimed to develop an effective surface pre-treatment method for recycled rubber particles to improve the sound insulation properties of rubberized lightweight aggregate concrete. In this study, the control lightweight aggregate concrete mixture was prepared using lightweight expand clay aggregate as the coarse aggregate and furnace bottom ash (FBA) as the fine aggregate. The results showed that when all the FBA was replaced by the recycled rubber aggregate, the overall sound reduction level was 32.5 dB (A), which was already significantly higher than the 15.5 dB (A) achieved by the control concrete mixture prepared without rubber aggregates. A simple cement slurry coating pre-treatment method was developed to modify the surface of the recycled rubber aggregate. 10.9 dB (A) and 14.8 dB (A) further noise reduction were achieved when FBA was replaced by 50% and 75% of the pre-treated rubber aggregates, respectively. The dynamic Young's Modulus of the concrete mixtures was tested and the surface bonding of the concrete mixtures prepared with the pre-treated/un-treated rubber aggregate was also investigated. The results suggested that the pre-treatment method resulted in weaker bonding between the rubber aggregates and the cement paste, and thus increased the vibration absorption capacity and enhanced the noise insulation properties of the concrete.

Continuous ultrasound‐assisted fabrication of lightweight polypropylene foam with low thermal conductivity and excellent sound insulation properties

Ultrasonic oscillation as a new polymer processing technology, was introduced into the polymer melt to improve the high melt strength Polypropylene (HMSPP) foaming ability, the effect of the ultrasonic oscillation power, Azodicarbonamide (AC) and talc content on the cell morphology, cell size, apparent density, cell density and nucleation density of the HMSPP foam was systematically studied. When the ultrasound and talc were introduced into the HMSPP melt, the HMSPP foam had a larger cell density and smaller the size as well as more uniform distribution. Interestingly, when the talc was introduced into the HMSPP, the cell morphologies changed from sphere to oval. Compared to the HMSPP foam without ultrasonic oscillation, the minimum thermal conductivity of the HMSPP foam with ultrasonic power 100 W reached 0.055 W/mK. When the talc was introduced into HMSPP melt, the average sound transmission loss value of the HMSPP foam were enhanced, and reached 30.37 dB, which was 13.7% higher than that of the HMSPP foam without talc and ultrasonic oscillation. The ultrasonic‐assisted extrusion foaming had a promising to construct a new method to continuously and rapidly fabricate polymer foam with low thermal conductivity and excellent sound insulation properties. POLYM. ENG. SCI., 58:1678–1684, 2018. © 2017 Society of Plastics Engineers

Sound insulation properties in low-density, mechanically strong and ductile nanoporous polyurea aerogels

Aerogels are quasi-stable, nanoporous, low-density, three-dimensional assemblies of nanoparticles. In this paper, an extremely high sound transmission loss for a family of ductile polyurea aerogels (e.g., over 30dB within 1 to 4kHz at bulk density 0.25g/cm3 and 5mm thickness) is reported. The fundamental mechanisms behind the aerogel acoustic attenuations are investigated. Sharing striking similarities with acoustic metamaterials, initially, aerogels are studied via a one-dimensional multi degree-of-freedom mass-spring system. Different effects such as spring constant disparity are investigated in regards to the structural vibration wave transmission loss. Results are given for different configurations consistent with the aerogel nano/microstructures. A significant wave attenuation is observed by considering a random spring distribution. In the next step towards modeling such a complex hierarchical and random structural material, the continuum Biot's dynamic theory of poroelasticity is implemented to analyze the experimental sound transmission loss results. In this framework, a two-dimensional plane strain analysis is considered for the interaction of a steady state time-harmonic plane acoustic wave with an infinite aerogel layer immersed in and saturated with air. The effects of bulk density and thickness on the aerogel sound transmission loss are elucidated. By comparing the theoretical results with the experimental observations, this study develops a qualitative/quantitative basis for the dynamics of the aerogel nanoparticle network as well as the air flow and solid vibroacoustic interactions. This basis provides a better understanding on the overall acoustic properties of the aerogels that might also be helpful in the design of the future hierarchical materials.

THE CONSTRUCTION OF A COMPOSITION BASED ON MAGNESIA BINDER WITH PEAT

Obtained building material based on magnesia binder with different content of peat (0 to 90 %), on a specially developed technique. As a binder used PMK 87, for mixing mixtures used aqueous solution of magnesium chloride and peat from the Ivanovo region. It were determined such physical and physico-mechanical properties of the investigated material as the compressive strength and the density. The strength characteristics of silicate bricks, ceramic bricks and the investigated material based on magnesia binder and peat was analyzed and compared. It is established that the samples of construction material with content of peat not exceeding 40 wt.% can be attributed to the materials of structural purpose by its compressive strength. Samples of the material with content of the peat 40% have a density 943,75 kg/m3, that provides good heat and sound insulation properties. It is revealed that the solution of the raw material mixture of magnesia binder, peat, the solution of bischofite is optimized to place, and the material gets at least 85% of its strength during 30 days.

LIGHTWEIGHT SLAB CAST OVER PRECAST JOISTS

Precast-monolithic house-building in domestic and world practice is a significant part in the mass construction. We propose a relatively large number of designs of precast-monolithic buildings, as well as its individual elements. Despite this, we cannot say that found the most effective constructive solutions able to satisfy the requirements of consumers (future residents) and builders. On this basis, we developed quite effective, from the point of view of construction and further operation, a constructive solution of light weight precast-monolithic overlap. Some features offered are overlapping: smaller mass, compared with beams of heavy concrete; increased heat and sound insulation properties; optimal use of the structural properties of heavy and light precast monolithic concrete and longitudinal reinforcement, depending on the stage of construction. The author has carried out in this article the results of numerical studies the proposed design of precast-monolithic overlap, confirming its compliance with the requirements of 1st and 2nd group of limit States.

A mobility based vibroacoustic energy transmission simulation into an enclosure through a double-wall panel.

Double-wall panels are known for their superior sound insulation properties over single wall panels as a sound barrier. The sound transmission phenomenon through a double-wall structure is a complex process involving vibroacoustic interaction between structural panels, the air-cushion in between, and the secondary acoustic domain. It is in this context a versatile and a fully coupled technique based on the finite-element-boundary element model is developed that enables estimation of sound transfer through a double-wall panel into an adjacent enclosure while satisfying the displacement compatibility across the interface. The contribution of individual components in the transmitted energy is identified through numerical simulations.

Analysis of impact sound insulation properties of wooden joist and cross laminated timber (CLT) floor constructions

During the last years, there has been an increased interest of developing lightweight constructions with improved sound insulation properties compared to previous, well-known solutions. There have been a progress on prediction tools as well as new solutions, for instance, from the WoodWisdom-Net project “Silent Timber Build.” Previous research establish the fact that including the frequency range below 100 Hz is crucial to get satisfying correlation between perceived and measured impact sound insulation quantities. Research work at SINTEF Building & Infrastructure concerning lightweight floor constructions include therefore frequencies down to at least 50 Hz. The paper will present analysis of a number of laboratory measurement results from joist floor constructions and CLT floor constructions. The paper will focus on the most challenging parameter, the impact sound insulation including the spectrum adaptation term CI,50-2500. Analysis will include parameters such as the mass of the floors, the height of the floors, and of course structural connections and properties of the resilient layers involved. Improved low frequency properties introduce of course more mass and or stiffness of the floor, but the result also show that optimization of the contributing components and material properties is necessary for the development of robust and environmental friendly solutions.

Impact of sound insulation quality in dwellings on its financial value

A lot of research has been already done on the assessment and improvement of sound insulation quality of partitioning elements in dwellings. Fewer studies have addressed the impact of acoustic improvements on those elements. Very little information is available on the impact of sound insulation properties on the global real estate value of dwellings as a hole. This contribution reports on the analysis of questionnaires and interviews concerning the overall satisfaction of dwellers about the acoustic comfort at their homes. The importance that people living in apartment flats in Slovakia give to their acoustic comfort at home is addressed, with the part of their budget that they would potentially consider to spend for improving it used as a measure.

Measuring the sound insulation of an external thermal insulation composite system (ETICS) by means of vibrometry

The impact of External Thermal Insulation Composite System (ETICS) on acoustic properties of external walls has been already examined. Probably the most fundamental research was carried out in Germany (Weber). The effect of thickness and dynamic stiffness of ETICS, as well as mass of external plaster, on decreasing of wall sound insulation was demonstrated. In this paper, the mass spring mass resonances (m-s-m) were investigated, in case of a massive external wall with ETICS. Application of ETICS increases the sound insulation of walls in the mass-law dominated frequency range by about 12 dB/oct. However, in the low frequencies ETICS decrease sound insulation due to resonant effects, which become very prominent in traffic noise situations. This contribution presents how vibrometry measurements can be useful for ETICS sound insulation properties measurement.

The sound insulation property of composite from waste printed circuit board and unsaturated polyester

The sound insulation property of Waste printed circuit boards (WPCBs)/unsaturated polyester (UP) composite plate has been investigated. The effect of WPCB particle size and mass ratio on the surface density, elastic modulus and weighted sound reduction index has been studied. The results showed that WPCB addition caused the surface density increase especially for coarse particle because of the metal particle existence. The elastic modulus value was susceptible to the UP sufficiency to high WPCB mass ratio. The WPCB-UP composite plate shows sound insulation application potential because the maximum weighted sound reduction index of composite plate with particle size <0.71 mm reaches 28.4 dB. The composite sound transmission loss, which is the sound insulation property at different frequency, was measured by the four-microphone impedance tube method in the frequency range from 100 to 3150 Hz. The theoretic resonance frequencies predicted by the stiffness and mass laws were close to the experimental ones. The STL difference in stiffness-controlled region was more obvious than that in mass-controlled region because the addition of WPCB leaded to much greater increase in the stiffness than that in surface density.

The cell growth-induced orientation of mica in lightweight flexible poly (vinyl chloride) foams and its enhancement on sound insulation

The lightweight flexible poly(vinyl chloride) (PVC)/mica composite foams with low density (0.51 g/cm3) which is 40–60% reduction and high sound insulation performance (an average STL of 28.3 dB) were prepared in this work. And the influences of mica content and foaming time on the cell morphology, mica distribution, and sound transmission loss (STL) were investigated. It was observed that the PVC/mica foams not only showed good sound insulation properties, but also maintained ultra-light in weight when the mica content was below 10 wt%. In addition, as the foaming time became longer, the cell density increased and the cell-wall thickness decreased. As a result, the bi-axial stretching induced by the cell growth would drive the mica platelets to orient along the thin cell walls, which significantly increased the sound insulation properties. Simultaneously, the flexibility and reusability of the foams were tested by cyclic compression. When the mica content was below 10 wt%, the PVC/mica composite foams showed low compressive stress and low permanent strain.