Acoustic Insulation Performance Research Articles

Uncertain sound transmission loss of composite laminated plates with embedded viscoelastic damping layer

Laminated composite structures have been widely applied in the engineering field due to their excellent capacities such as high specific stiffness, high specific strengths and tailorable anisotropic elastic properties. Embedding the viscoelastic damping layers into the laminated composites to construct co-cured composite damping structures provides an effective way to improve the sound insulation capability. In this paper, a semi-analytical model is proposed to investigate the sound transmission loss (STL) of composite laminated structure with embedded viscoelastic damping layer considering its frequency-dependent characteristic. Furthermore, Polynomial Chaos Expansion (PCE) method in conjunction with the semi-analytical model is employed for uncertainty propagation analysis of sound transmission loss of the composite laminated plates subjected to uncertain parameters of frequency-dependent interleaved viscoelastic damping layer. Moreover, numerical simulations are conducted to demonstrate the impacts of the uncertain parameters of the embedded viscoelastic damping layer on the STL of the composite laminated plate. Finally, experiments are carried out to investigate the uncertain acoustic insulation performance of composite laminated plates with embedded damping layer. Key words: Laminated composite structure; Sound transmission loss; Uncertainty analysis; Damping layer; Frequency-dependent properties

Sound transmission loss analysis of double-walled sandwich functionally graded carbon nanotube-reinforced composite magneto-electro-elastic plates under thermal environment

Sandwich structures with functionally graded (FG) cores have gained interest in vibroacoustic applications. This article considers the vibroacoustic properties of double-walled sandwich magneto-electro-elastic (MEE) plates with a functionally graded carbon nanotube-reinforced composite (FG-CNTRC) core layer in a thermal environment. A coupled multiphysics model is developed based on third-order shear deformation theory (TSDT) and acoustic-structure interaction. Special attention is paid to the transmission loss of this arrangement for simply supported and clamped boundaries for four different kinds of CNT distributions, namely, UD, FG-V, FG-O, and FG-X. Sound velocity potential, normal velocity continuity conditions, and Hamilton's principle are used to generate the coupled vibroacoustic equations, which are then solved using the Galerkin method. The effects of boundary conditions, CNT distributions, cavity depth, multiphysics coupling fields, and temperature on the STL are comprehensively studied. The results provide guidelines for tailoring the dynamic response of these materials to achieve enhanced acoustic insulation performance. It enhances fundamental understanding and enables the engineering design of multilayered composite panels with optimized vibration and noise control capabilities.

Development of eco-friendly wall insulation layer utilising the wastes of the packing industry

Efficient thermal insulation materials considerably lower power consumption for heating and cooling of buildings, which in turn minimises CO2 emissions and improves indoor comfort conditions. However, the selection of suitable insulation materials is governed by several factors, such as the environmental impact, health impact, cost and durability. Additionally, the disposal of used insulation materials is a major factor that affects the selection of materials because some materials could be very toxic for humans and the environment, such as asbestos-containing materials. Therefore, there is a continuous research effort, in both industry and academia, to develop sustainable and affordable insulation materials. In this context, this work aims at utilising the packing industry wastes (cardboard) to develop an eco-friendly insulation layer, which is a biodegradable material that can be disposed of safely after use. Experimentally, wasted cardboard was collected, cleaned, and soaked in water for 24 h. Then, the wet cardboard was minced and converted into past papers, then cast in square moulds and left in a ventilated oven at 75 °C to dry before de-moulding them. The produced layers were subjected to a wide range of tests, including thermal conductivity, acoustic insulation, infrared imaging and bending resistance. The obtained results showed the developed material has a good thermal and acoustic insulation performance. Thermally, the developed material had the lowest thermal conductivity (λ) (0.039 W/m.K) compared to the studied traditional materials. Additionally, it successfully decreased the noise level from 80 to about 58 dB, which was better than the efficiency of the commercial polyisocyanurate layer. However, the bending strength of the developed material was a major drawback because the material did not resist more than 0.6 MPa compared to 2.0 MPa for the commercial polyisocyanurate and 70.0 MPa for the wood boards. Therefore, it is recommended to investigate the possibility of strengthening the new material by adding fibres or cementitious materials.

Numerical and experimental investigation of sound transmission through roller shutter boxes

Roller shutter boxes are essential components of building facades, providing crucial thermal and acoustic insulation. Conventional laboratory tests have been traditionally used to evaluate the sound transmission of roller shutter boxes. However, these tests can be expensive and lack repeatability and reproducibility, especially in the low-frequency range. To overcome these limitations, this study aims to introduce an advanced numerical model capable of accurately predicting the vibroacoustic response of roller shutter boxes and optimizing their acoustic insulation performance. The proposed numerical approach utilizes the finite element method to model the various solid and fluid domains within the roller shutter box structure. To capture the behavior of the poroelastic layers, a mixed displacement–pressure formulation of the Biot poroelasticity equations is employed. Excitation of the structure is achieved using a diffuse field comprising a superposition of plane waves with random phases and directions, while the resulting sound radiation is computed utilizing the infinite elements method. To validate the proposed numerical model, a comparison is made with results obtained from laboratory tests, and the experimental protocol is thoroughly described. The practical application of the proposed numerical method extends to the investigation of several influential factors on the acoustic behavior of roller shutter boxes, including assembly conditions, the positioning of poroelastic layers, and the inclusion of heavy masses.

Polyimide/SiO2 composite aerogels with excellent thermal and sound insulation properties prepared by confined filling method

Aerogels have enormous potential in integrated thermal insulation and noise reduction applications. According to the knowledge of the favorable mechanical and acoustic properties of honeycomb structures. We employed anisotropic “honeycomb-like” polyimide (PI) aerogels as the matrix and utilized a confined filling strategy to directionally filled continuous SiO2 aerogels into the PI aerogel matrix. This resulted in the creation of an exceptional organic–inorganic composite aerogel (PISis) with outstanding thermal and acoustic insulation performance. The radial thermal conductivity of PISis ranged from 22.37 to 27.65 mW·m−1·K−1, and the initial decomposition temperature was approximately 524–557 °C. In the frequency range of 500–6300 Hz, the average sound transmission loss (STL) of the 18 mm thick composite material reached 30.67 ∼ 31.89 dB, and the compressive strength at 10 % strain is 0.416 MPa. The PISis exhibits a density ranging from 0.1012 to 0.1302 g/cm3. These make it an ideal lightweight, high-strength, and efficient material for thermal and acoustic insulation.

Improving the noise insulation performance of vibro-acoustic metamaterial panels through multi-resonant design

In the search for lightweight solutions with favourable noise and vibration attenuation, locally resonant vibro-acoustic metamaterials have emerged as a promising candidate due to their stop band behaviour. When used in a sound transmission context, vibro-acoustic metamaterial panels allow to greatly improve the acoustic insulation in a targeted frequency range. However, their peak insulation is typically followed by a strong insulation dip, which hampers their broad applicability. Recently, a dip reduction concept was proposed to reduce this insulation dip using multiple resonances. Although promising, this concept has not yet been demonstrated on a realizable metamaterial panel of representative dimensions. Therefore, this work extends and demonstrates the concept of dip reduction to address the sound insulation dip of a realizable metamaterial panel, while preserving peak insulation performance and total mass addition. To this end, a design framework is presented based on lumped parameter and finite-element model optimizations to efficiently achieve practically realizable dip-reduced metamaterial panel designs. A multi-resonant metamaterial panel is realized and its acoustic insulation performance compared to a conventional metamaterial panel of similar total mass. Acoustic insertion loss measurements demonstrate a clearly improved insulation dip, while peak insulation performance is preserved.

Hierarchical polyimide-polyborosiloxane host-guest structure with impact resistance, acoustic and thermal insulation performance for electro-stability applications

The ubiquitous existence of mechanical impact, sound pollution and thermal damage conferred severe risks to both individuals and devices, which catalyzed increasing demand for advanced protective materials. Though biomimetic structures have motivated the development of high-performance protective composites against a simple threat, the realization of multi-mode interference protection remained a challenging issue. This work proposed a host-guest structural composite, consisting of viscoelastic polyborosiloxane (PBS) dispersively distributed in porous polyimide (PI) matrix. The resulting PI-PBS composite presented effective impact force attenuation (85.8%-92.3%), arising from the multi scale energy dissipation mechanism of strain-rate enhancement, structural densification and synergistic stress transfer, which was intuitively demonstrated by an innovative mechano-discoloration approach. The viscous dissipation effect endowed PI-PBS with extraordinary acoustic insulation effectiveness in a wide frequency region (1–6.3 kHz). Due to the low thermal conductivity (0.051 W/(m·K)), PI-PBS presented good thermal insulation performance over a wide temperature range (∼ −80 – 300 °C). The structure dependence of thermal conduction behavior was revealed via FE simulation, while demonstrating various applications in dynamic infrared thermal camouflage. PI-PBS, as a functional wrapping, provided reliable guarantee for electrical stability of conductive elements against impact, ultrasonic and thermal interferences, which indicated significant value in electromagnetic shielding, sensing and electrothermal fields. Therefore, PI-PBS could assist in efforts to lighten, integrate and intelligentize protective materials in the future.

Low-frequency sound insulation of honeycomb membrane-type acoustic metamaterials with different interlayer characteristics

The membrane-type structure that can achieve excellent sound insulation characteristics under lightweight conditions is widely concerned, but it generally involves a small mass block attached to a thin membrane. Although this kind of design can obtain better acoustic insulation performance, the mass block will cause installation and manufacturing issues in industrial applications. This paper presents a multilayer honeycomb membrane-type acoustic metamaterial with an interlayer structure. Similar to the mass block, the interlayer structure makes less sound energy transmitted by varying the eigenmode characteristics of the membrane. Considering the integrated design of the interlayer structure, the issues of installation and manufacturing are solved and the sound transmission loss is enhanced on the fixed overall dimension and small additional mass. The results indicate that the design of interlayer structures can break the bottleneck of ultrathin and lightweight requirements. Meanwhile, the symmetry of interlayer position can lead to the shift in transmission loss valley to a higher frequency, achieving high sound insulation in a wide frequency range.

Acoustic properties of glued laminated bamboo and spruce-pine-fir

Noise pollution has become a worldwide issue, which has a negative effect on human health. The sound reduction index and absorption coefficient of glued laminated bamboo (glubam) and spruce-pine-fir (SPF) were firstly measured in this study by using the impedance tube method. The effect of moisture content on the acoustic performance of these materials was also investigated. Experimental results revealed that for thick-strip glubam and SPF, the higher moisture content, the higher sound reduction index but lower sound absorption coefficient. However, moisture content does not have an obvious effect on acoustic properties of thin-strip glubam. By comparing with other materials, it can be found that glubam and SPF have relatively high normal-incidence transmission loss but low absorption coefficient and noise reduction coefficient. Glubam shows the similar but even better acoustic insulation performance than SPF, which confirms the possibility of using glubam as an alternative of wood materials. Moreover, a finite element model was built up to simulate the measurement of sound transmission loss in an impedance tube. Some parametric studies were then conducted using the finite element model to prove the effectiveness of increasing thickness, using composites and double-layer panels on improving the soundproof performance of materials.

Bio-based aggregate in the production of advanced thermal-insulating concrete with improved acoustic performance

Concrete is the most utilized man-made building material and its global production reaching 25 billion tons per year represents a huge burden on our environment. Unsurprisingly, a lot of effort is dedicated to searching for suitable replacing materials of concrete constituents, e.g. of mineral aggregate that usually forms 70–80 vol% of fresh concrete mix, not only to reduce the depletion of our natural resources, but, at the same time, to improve some of the concrete properties. For example, dense building materials are not very effective in acoustic-insulation performance. In this context, renewable resources can provide a possible solution in the preparation of advanced concrete composites that will help to reduce noise originating in high populated urban and/or industrialized areas. This paper is focused on the application of carbonized lightweight bio-based aggregate (BA), having about 63 % lower thermal conductivity compared to the traditional ones, in the manufacturing of lightweight concretes which, related to BA quantity in mixes, dispose with considerably mitigated thermal transport properties and enhanced acoustic-insulation function. Traditional dense aggregate was replaced with the bio-based alternative in the amount of 0–100 vol% and the batch water content was adjusted to keep similar consistency (class S4) of fresh concrete mixes. After 28 days of water curing, the development of dry bulk density, open porosity, flexural and compressive strengths as well as thermal and acoustic performance in the dependence on bio-based aggregate content were determined on hardened specimens. Experimental investigation revealed significant lightening effect of BA particles having a honeycomb-like porous structure and thus promoting the high thermal and acoustic performance of developed concretes. Accordingly, hardened concrete samples with alternative aggregate content only showed 7.5 times lower thermal transport and about 16.2 % improved acoustic performance compared with ordinary dense concrete. In addition, lower BA dosages (up to 50 vol%) allowed to produce concretes disposing sufficient strength parameters – average flexural strength about 6.5 MPa and compressive strength about 27.0 MPa maintaining their usage for structural purposes. Furthermore, bio-based aggregates are sorted among renewable resources that may mitigate environmental impacts connected with the quarrying of traditional filling materials, and thus contribute to higher sustainability of concrete production.

Bioinspired periodic panels optimized for acoustic insulation.

The design of structures that can yield efficient sound insulation performance is a recurring topic in the acoustic engineering field. Special attention is given to panels, which can be designed using several approaches to achieve considerable sound attenuation. Previously, we have presented the concept of thickness-varying periodic plates with optimized profiles to inhibit flexural wave energy propagation. In this work, motivated by biological structures that present multiple locally resonant elements able to cause acoustic cloaking, we extend our shape optimization approach to design panels that achieve improved acoustic insulation performance using either thickness-varying profiles or locally resonant attachments. The optimization is performed using numerical models that combine the Kirchhoff plate theory and the plane wave expansion method. Our results indicate that panels based on locally resonant mechanisms have the advantage of being robust against variation in the incidence angle of acoustic excitation and, therefore, are preferred for single-leaf applications. This article is part of the theme issue 'Wave generation and transmission in multi-scale complex media and structured metamaterials (part 2)'.

Improving the sound absorption of a highly deformable nanocomposite foam based on ethylene-propylene-diene-monomer (EPDM) infused with multi-walled carbon nanotubes (MWCNTs) to absorb low-frequency waves

In this study, an elastomeric nanocomposite foam was fabricated on the basis of ethylene-propylene-diene-monomer (EPDM) rubber filled with multi-walled carbon nanotubes (MWCNTs) to absorb low-frequency acoustic waves. The effects of adding MWCNTs on the cellular structure, viscoelastic behavior, and sound absorption characteristics were studied. Samples containing slight loadings of MWCNTs with increased damping factor and decreased pore sizes showed high viscose motions with superior sound absorption characteristic. The results revealed that the nanocomposite foam sample with only 0.1 phr (parts per hundred rubber) MWCNTs offered the best sound absorption coefficient with a sharp peak (0.98) within the frequency range of 500–1000 Hz. This can be justified by the dissipation of acoustic energy through vibration and deformation of the flexible cell walls due to the highly elastic matrix, high porosity and airflow resistivity of the fine partially reticulated cellular structure. With further MWCNTs loadings beyond the optimum level, the cell size was reduced dramatically, leading to reduction in porosity and excessive increase in air flow resistivity. These factors resulted in poor sound absorption feature. Moreover, the sound insulation performance of the nanocomposite foams was characterized, and it revealed the improving effect of MWCNTs, especially in high loading, by yielding a sound reduction index equal to 27–33 dB. According to the obtained results, the potential role of MWCNTs in the improvement of the acoustic absorption and sound insulation performance of EPDM foam can be inferred. Thus, a lightweight sound absorber with high resistance to harsh environmental conditions and excellent low-frequency sound absorption can be achieved by the infusion of nanoparticles.

The Prediction and Analysis of Acoustic Metamaterial Based on Machine Learning

Low-frequency noise is regarded as special environmental noise problem which has a serious impact on people’s lives. The traditional technology cannot effectively insulate the low-frequency noise, while the emergence of acoustic metamaterial makes it come true. This paper studies the acoustic insulation of membrane-type acoustic metamaterial. Due to different weights of the factor, an analytical method based on analytic hierarchy process (AHP) is proposed to analyze the affecting factors of acoustic insulation performance. The orthogonal array results show that the main factors affecting acoustic insulation are membrane thickness, membrane preload force and attached mass. A factor-weighted k-Nearest Neighbor (kNN) classification approach is proposed to predict different levels of acoustic insulation, which also provides a reference for the analysis of acoustic insulation. The experimental results demonstrate that when k = 3, the maximum classification accuracy of acoustic insulation is 98.2% by using AHP-kNN approach, which makes the accuracy for acoustic insulation is higher than other three baselines.

Acoustic and thermal performance of polypropylene nonwoven fabrics for insulation in buildings

Thermal insulation and acoustic absorption materials play a significant role in the characteristics of energy-saving and comfortable modern buildings. However, these two types of materials are generally developed independently. This study highlights the potential of lightweight polypropylene nonwoven fabrics for building applications and investigates how fabric structure affects thermal and acoustical properties. An industrial-scale melt spinning machine was used to produce polypropylene fibers at linear densities of 1.4 and 1.8 dtex. A semi-industrial needle punching line was used to fabricate nonwoven samples with three thicknesses (2, 3, and 4 cm), four porosities (0.83, 0.88, 0.93, and 0.96), and different in- and through-plane fiber orientation distributions. Totally, 31 samples were produced and their sound absorption and thermal insulation performance were assessed using impedance tube and guarded hot plate techniques. Accordingly, the thermal conductivity (Keff) and sound absorption average (SAA) of the samples could be engineered in the range of 0.0270–0.0404 W m-1K-1 and 0.270–0.675, respectively. It was found that fabrics made of finer fibers provide superior acoustic absorption and thermal insulation performance. An increase in through-plane fiber orientation adversely affected the thermal insulation properties, while its effect on acoustic properties depends on the porosity of samples and the sound frequency. The results of statistical analysis showed that in-plane fiber orientation does not have a significant effect on sound absorption behavior, except at frequencies between 4000 and 6300 Hz. It was also found that in-plane fiber orientation does not significantly affect the thermal insulation properties. The best acoustic and thermal performance were achieved by fibrous samples of layered structure made of 1.4 dtex fibers with a thickness of 3 cm (Keff =0.0278 W m-1K-1, SAA = 0.552) and 4 cm (Keff =0.0277 W m-1K-1, SAA = 0.675). The performance of these samples was compared with some commercial products and literature data. The results pointed to the superior acoustic and thermal properties of the designed samples.

Study of an insulating hemp-based bio-material: mechanical, thermal and acoustic properties

Currently there is a need to develop more sustainable and renewable materials compromised with the environment. From these needs, hemp stalk has great potential because it is mostly a waste material. Moreover, hemp shives are a lightweight material with a high insulating property. This study aims to increase the knowledge in a material made solely from stalk and ECF (elementary chlorine free) bleached eucalyptus kraft pulp and a second 100% recycled material where the kraft pulp is replaced by recycled cardboard fiber, also a vegetable coating is added to protect against moisture. The hemp/fiber ratio influence is studied. Samples are evaluated in terms of mechanical behaviour (compression and shear), thermal and acoustic insulation. To study the thermal insulation, a testing camera is used where the heat transfer through the material is measured in order to study the thermal resistance. A Kundt tube is used in the acoustic insulation study to calculate the absorption of sound waves in a range from 0 to 6500 Hz. The results show that by increasing the percentage of hemp, the mechanical properties increase (compression and shear). Also, the eucalyptus pulp acts as a binder between the shives; nevertheless, if there is not enough, the material is not stable. Therefore, a maximum of 70 wt.% of hemp is recommended. In the case of thermal insulation, better thermal resistance is obtained in the case of 60 wt.% of hemp, while in acoustic insulation a higher percentage of hemp have a high performance, reaching attenuation values greater than 0.8 for frequencies greater than 1000Hz. The carboard sample improves the shear and acoustic insulation performance. The coating improves the thermal resistance but worsens the acoustic insulation.

Research and design of broadband muffler based on second-order Helmholtz resonators

Noise is always a serious factor affecting people's quality of life. The most common sound-absorbing materials are porous materials, which work based on the principle that sound waves entering into the pores inside the material are subjected to air friction and viscous resistance, thus converting sound energy into heat. Porous materials have excellent performance of absorbing medium-frequency and high-frequency sound , but they are required to be thick enough to control the low-frequency sound waves with large wavelengths, which limits the application of porous materials in low-frequency noise control. In recent years, acoustic artificial structures have become a research hotspot, which can realize exotic effective acoustic parameters based on periodical structure or local resonance. Acoustic artificial structure provides a new material basis for noise control, in which Helmholtz resonator plays an important role because of its simple geometry. In this study, a broadband muffler is designed based on the second-order neck embedded Helmholtz resonator. In order to achieve low-frequency and broadband sound insulation with a limited number of units and structure length, the second-order resonator is chosen as a basic structure unit, which has a stronger low-frequency noise reduction capability and has one high-frequency transmission loss peak more than a conventional Helmholtz resonator. The acoustic characteristics and insulation performance of second-order resonators are analyzed through theoretical calculation, simulation calculation and experimental test. Then, based on the theoretical model and empirical rules, a broadband muffler composed of nine second-order resonators is designed by carefully adjusting the geometry parameters of each resonator. The three-dimensional printed resonators are installed on the side wall of a square standing wave tube for experimental measurement. In the experiment, the transmission loss curve of the muffler is measured by the two-load method. The result shows that the designed muffler has good sound insulation performances in a frequency range of 267–927 Hz, with the whole transmission loss above 20 dB and the maximum sound insulation up to 60 dB. The experimental result is consistent with the calculation result and simulation result. The muffler has simple structure and high practicability, which will have a wide application prospect in noise control engineering.

Towards aeroacoustic measurements under hyperbaric condition

Full scale experimental aeroacoustic measurements are often impractical due to the prohibitively high costs associated with full scale models and large facilities capable of far-field acoustic measurements. Although small scale models can provide useful acoustic data, this scaling is limited by the inability to achieve full scale equivalent aerodynamic conditions at smaller scale. However, aerodynamic similarity can theoretically be achieved using much smaller models under hyperbaric conditions. While promising, microphones and anechoic materials used in acoustic experimentation are not explicitly designed for use in such conditions, and so their behavior must be verified. To characterize the response of condenser microphones at elevated pressures, a pistonphone style calibrator was developed to operate over a range of pressures. Likewise, for the anechoic materials, an impedance tube was developed to evaluate their performance at elevated pressures. The performance of these systems under atmospheric pressure and hyperbaric conditions is discussed, along with details of the experimental method, and observed microphone response, and acoustic insulation performance at high pressure.

Sustainable Acoustics for Powertrain Noise Reduction

<div class="section abstract"><div class="htmlview paragraph">A common way to reduce the noise of automotive powertrains, both with internal combustion engine (ICE) and electric driveline, is to cover their noise radiating areas. However, the parts used for this purpose, besides being effective from the NVH standpoint, also have to fulfil several non-NVH requirements. For ICE, they have to provide a certain level of thermal insulation while favoring the reduction of fuel consumption and CO2 emissions. For electric powertrains, lightweight, environmental footprint and sustainability become preponderant in the design of engine covers. Combining these multidimensional requirements, a new fiber-based mono-material product for engine-mounted applications is proposed. It is able to provide optimum noise protection in the passenger cabin and greater driving comfort while keeping high level of sustainability, good heat resistance and relatively low weight. This paper deals with the acoustic benchmarking of the newly developed product against various more traditional solutions available on the market. Using an experimental approach, the newly developed solution is positioned against the other bills of materials, in terms of acoustic absorption and insulation performance first at material level. Then, an acoustic performance comparison is carried out at part level on an electric motor mock-up.</div></div>

The impact of the cracks in the window

When we talk about the acoustic insulation performance of a building facade, we know that its weakest link is the frame that makes it up. We soon know that great performance on the part of this component is necessary so that the facade assembly can obtain high levels of insulation. Although there are several lines and models of frames, each with two unique characteristics and varied acoustic performance, they have a similarity in their result curve. where at high frequencies it becomes a decisive point for your result. In this work, we will analyze the vulnerable points of a typology of mitering, focusing on its cracks and the impact that each one has on its result; as well as measures that can be taken so that the frame can acquire great acoustic performance, without changing the profile lines or glass thickness.

Influence of Waste Tire Rubber Particles Size on the Microstructural, Mechanical, and Acoustic Insulation Properties of 3D-Printable Cement Mortars

3D printing technologies of construction materials are gaining ground in the building industry. As well documented in the literature, these advanced manufacturing methodologies aim to reduce work-related injuries and materials waste, enhancing architectural flexibility which would enable more sophisticated designs for engineering and aesthetic purposes. In this framework, the development of functional and eco-sustainable printable materials represents an extremely attractive challenge for research, promoting digital fabrication to reach its maximum cost-effective and technological potentials. The use of recycled tire rubber particles in 3D printable Portland-based compounds is an exclusive contribution in this field. This line of research aims to integrate the well-known engineering performances of rubber-cement materials with the advanced peculiarities of additive manufacturing methodologies. As an innovative contribution, the authors propose here a detailed study on the possible relationship between rubber particle size and technological properties of the 3D printable mix. Specifically, two groups of continuous size grading polymer aggregates (0-1 mm rubber powder and 1-3 mm rubber granules as fine and coarse fractions, respectively) were analyzed in terms of impact on rheology, print quality, microstructure, mechanical properties, and acoustic insulation performance. Concerning the print quality, rubber aggregates altered the fluidity of the fresh mix, improving the adhesion between the printed layers and therefore enhancing the mechanical isotropy in the post-hardening sample. A remarkable influence of the rubber gradation on the compounds’ behaviour was found in hardened properties. By comparing the rubberized compounds, the fine polymer fraction shows greater interfacial cohesion with the cement paste. However, more significant mechanical strength loss was found due to a greater reduction in density and increased porosity degree. On the other hand, mortars doped with larger rubber particles tend to have a higher unit weight, finest pore distribution, minor mechanical strength drop, and higher ductility but worse interface binding with the matrix. Regarding the acoustic insulation properties, a proper balance between rubber powder and granules in the mixes allows to obtain comparable/superior performance compared to plain mortar but the effect of the aggregate size is strongly dependent on the sound frequency range investigated. Future findings revolve around applicability studies of these formulations in civil and architectural fields, benefiting from the design flexibility of 3D printing. Doi: 10.28991/cej-2021-03091701 Full Text: PDF