Floor Impact Sound Insulation Research Articles

Computational prediction of impact sound insulation of a timber floor excited by an ISO standard tapping machine

During the last decades, researchers have actively developed procedures to predict impact sound insulation of timber slabs and floors using the finite element method (FEM). Since the simulations have mainly been performed in the low frequencies, a full understanding of their suitability for research and development (R&D) purposes has not yet been created. The object of the study reported in this paper was to determine the applicability of a modern FEM simulation procedure for predicting the normalised impact sound pressure level Ln of a full timber floor, when information provided by material manufacturers is used as input data. Force excitation caused by the ISO standard tapping machine was determined utilizing explicit time integration and FEM. The modelling of sound radiation itself was performed in a frequency domain FEM analysis. The models of a timber floor in its construction stages were constructed before the laboratory measurements of impact sound insulation so that the set-up corresponded to a simulated R&D task. Based on the prediction results, the applied procedure was considered suitable for R&D purposes and needs for further studies were identified.

Review of floor impact sound insulation performance measurement evaluation methods and timber floor specifications in Japan

Since the 1970s, heavy-weight floor impact noise has been a concern in Japan, prompting the development of unique measurement and evaluation methods standardized by JIS (Japanese Industrial Standards). JIS A 1418-1 specifies the measurement method for light-weight floor impact sound insulation performance, while JIS A 1418-2 defines the measurement method for heavy-weight floor impact sound insulation performance. Two types of standard impact sources, namely car-tire impact source and rubber ball impact source, are specified for measuring the heavy-weight floor impact sound insulation performance. JIS A 1419-2 defines the evaluation method for floor impact sound insulation performance. These methods differ from the international ISO standards, making performance comparison challenging. This paper provides an overview of these Japanese methods. Furthermore, since the enforcement of "the Act on Promotion of Use of Wood in Buildings to Contribute to the Realization of a Decarbonized Society," construction of timber buildings has been promoted in Japan with the aim of encouraging wood usage and contributing to the SDGs (Sustainable Development Goals). However, the floor impact sound insulation performance of timber floors tends to be low, with various specifications for timber floor cross-sections differing among private companies. This paper introduces these specifications and also compares driving-point impedances.

Heavy-weight impact sound insulation characteristics related with vibrational properties of Korean domestic CLT slabs with different species and joint types

Korea has the world's most strict inter-floor noise regulations. In order to build an apartment house with more than 30 units, it must meet the minimum requirement of impact sound level, single number quantities of 49 dB. These regulations make it hard to expand residential tall wood building in Korea. For making quality satisfied CLT floors, as the preliminary investigations, the effects of wood species and CLT panel joints on the vibration and sound insulation performance of CLT were analyzed. The natural frequency range of the CLT slabs is from 20 Hz to 22 Hz. There were no significant differences depending on wood species and CLT panel joint type. As the stiffness of the slabs increased, the floor impact sound insulation performance also improved. The deflection model for CLT slabs was developed and validated with the actual deflection derived by acceleration spectrum. The measured value was 62 ~ 87% of the predicted value.

Floor impact sound insulation performance of Korean domestic cross-laminated timber floors and the influence of resilient materials' dynamic stiffness

In this study, the floor impact sound insulation performance of floors made of korean domestic cross-laminated timber panels and with a resilient layer under concrete topping was evaluated. The properties of resilient materials used in the floors were measured to evaluate their influence on floor impact sound insulation performance. The results indicate that the highest reduction levels were provided by glass fiber, expanded polystyrene and wood fiber, in diminishing order, for both heavy-weight and light-weight floor impact sounds. Through the evaluation of dynamic stiffness and single-number quantities, a high correlation was observed at 125 Hz and 500 Hz for heavy-weight floor impact sounds and across all octave bands for light-weight floor impact sounds. The analysis of dynamic stiffness and single number quantity revealed a high correlation in both heavy weight and light weight floor impact sound. Lower dynamic stiffness was confirmed to be advantageous for reducing floor impact noise.

Ribbed floors with optimized thickness distribution for maximized broadband impact sound insulation

Impact sound insulation of floors is one of the main concerns when designing multi-story buildings. While conventional floor systems use flat or regularly ribbed configurations, interesting opportunities to improve performance are given by enhancing the design of the load-bearing slab. In this work, we propose a methodology to maximize broadband impact sound insulation by designing slabs with a non-uniform material thickness distribution, which is numerically optimized. In the design process, efficient and accurate sound insulation predictions are employed through a detailed finite element floor model coupled with a diffuse room model. In particular, we minimize a Single Number Quantity (SNQ) that represents the aggregate broadband sound pressure level in the receiving room under point-load excitation. The design of single slab floors is considered first. Results indicate that, even if the optimization effectively minimizes the sound pressure level in the different third-octave bands, it does not lead to noteworthy decreases in the SNQ. The design of floating floors is then considered. In this case, a better overall performance is obtained, corresponding to significant improvements at low frequencies and a slight degradation at high frequencies, where, nevertheless, floating floors already perform well. This slight high-frequency decline is linked with the resonances of the thin sub-plate regions present between the optimized ribs, akin to what is observed in waffle ribbed floors. Finally, the robustness of the optimized results against changes in the initial guess is assessed by showing that no SNQ improvements are obtained when transitioning from flat to waffle ribbed initial design.

Computational prediction of impact sound insulation of a full-scale timber floor applying a FEM simulation procedure

During the recent decades, simulation procedures involving the finite element method (FEM) have been developed to enable prediction of impact sound insulation of timber slabs and floors. FEM simulations have previously been applied for timber floors mainly in low frequencies despite their evident ability to operate over a wide frequency range. Additionally, the validation processes have involved calibrations and experimental modal analyses which can seldom be performed in product development tasks concerning full structures. The purpose of this research was to study the applicability of a FEM simulation procedure to predict normalised impact sound pressure levels Ln of a full-scale timber floor if material data provided by the product manufacturers is used. The floor was studied at three construction stages where the FEM simulations were performed for the bare floor and the rib slab, and the floor covering was considered in the post-processing stage in case of the full floor. The impact force excitation generated by the ISO standard tapping machine was described with the recently published procedure involving explicit dynamics analysis. To serve the purposes of this study, the FEM models were fully constructed before the measurements were carried out. According to the results, the 1/3-octave Ln of the full floor and the floor without covering was predicted with a 0 to 9 dB accuracy depending on the frequency band and the single-number quantities with a 0 to 4 dB accuracy. The single-number quantities of the bare rib slab were underestimated with the simulations by 4 to 5 dB. Probable causes for the discrepancies between the simulation and measurement results pointed mainly to the uncertain material properties but possibilities for modelling inaccuracies could not be excluded.

Current Performance of Floor Impact Sound Insulation in Wooden Apartment Buildings in Hokkaido

In Hokkaido, Japan, technological developments have been introduced to improve the floor impact sound insulation performance in wooden apartment buildings. However, such technological developments are not widely used, especially in rental properties. To effectively disseminate the required technology, it is vital to report examples of implementation. Therefore, we measured the performance of five types of wooden apartment buildings with high sound insulation performance and analyzed the results. The main results are listed below. (1) A relatively high performance was obtained by installing a floating floor and an independent ceiling. (2) For heavy weight floor impact sound insulation of a car tire source, a floating floor with a surface density of 60 kg/m2 or higher could achieve a performance of Li,Fmax,r,H(1)-60 or higher. However, in the case of a rubber ball source, vibration radiation noise from the wall surface of the lower floor is large, so it is necessary to consider vibration countermeasures. (3) For light weight floor impact sound insulation, sufficient performance cannot be obtained even with a floating floor. Therefore, carpet or wooden soundproof flooring should be used. (4) The light weight floor impact sound pressure level is high when the floor area of the sound receiving room is small.

Comparison of measurement methods of room sound energy for sound insulation performance evaluation at low frequencies

In the field measurement of acoustic performances, such as sound insulation and floor impact sound insulation, sound pressure level is usually measured to find the sound energy in a closed space. However, the sound pressure level at low frequencies such as the 63 Hz band depends on the measurement position due to the influence of the room eigenmodes, which leads to large uncertainties of the measured average sound pressure levels in rooms. In this study, several measurement methods of sound energy were applied to the low-frequency sound field of a mock-up room that simulates a source room in an RC apartment. Along with the standard sound pressure level measurement, the low-frequency procedure according to ISO 16283 series and acoustic energy density measurement using the combined particle velocity-pressure sensor were conducted, and their accuracies were evaluated based on the average sound pressure obtained by the grid-point measurement over the entire room.

Study on Heavy Weight Impact Sound Insulation of CLT Floor Slab and Reduction Performance with Floor Structure

Strategies and challenge for carbon neutrality by 2050 had become important issues all over the world. In South Korea, as a move toward carbon neutrality, interest in wooden buildings is growing continuously. In order to spread the wooden buildings, especially wooden multi-residential buildings, high floor impact sound insulation performance is required. In this study, we investigated the floor impact sound insulation performance of floor slabs with cross laminated timber (CLT) panels produced in South Korea. Moreover, laboratory measurements were conducted to grasp the reduction effect by floor covering. As a result, the heavy-weight impact sound insulation performance of CLT bare slab of its thickness of 150 mm is almost 17 dB lower than that of RC slab according to ISO717-2. Concrete topping and damping material are found to be effective to both heavy and light weight floor impact sound insulation.

Development of a dry-type double floor with high vibration isolation for improvement of floor impact sound insulation performance on CLT buildings

To improve the floor impact sound insulation performance of cross laminated timber (CLT) buildings, a box-type test chamber made of CLT was constructed, and the countermeasure using a dry-type double floor was investigated. Several specimens with different area density and bending stiffness of double flooring structure were prepared, and the materials of flooring and elastic floor posts were adjusted so that the natural frequency of each specimen was about 14 Hz when the specimen was considered as a single-degree-of-freedom system. The dry-type double flooring structure affected the response at the natural frequencies not only of the slab but of walls. When installing the dry-type double flooring structure, the influence of acoustic radiation from the ceiling surface was relatively high at lower frequencies, while at higher frequencies, the influence from the walls was relatively high. The installation of the dry-type double flooring structure resulted in an improvement in floor impact sound insulation performance.

Case study of sound insulation performance of a first pure timber 3-story elementary school in Japan

In Japan, "the Act on Promotion of Use of Wood in Buildings to Contribute to the Realization of a Decarbonized Society" promotes the use of wood in buildings in general. The school buildings as public buildings are being promoted to be constructed with timber construction since timber school buildings effectively improve the educational environment. This paper presents the measurement results of the sound insulation performance in "the Uozu City Municipal Hoshinomori Elementary School", which is a first all-timber construction 3-story elementary school in Japan. By adopting a dry-type double floor structure for the floor finish structure and an independent ceiling for the ceiling structure, the floor impact sound insulation performances of the classrooms were Lr-60 for both heavy-weight floor impact sound and light-weight floor impact sound when evaluated using JIS A 1419-2. Moreover, the recommended reverberation time values of the Architectural Institute of Japan Environmental Standards were generally satisfied by installing dressed rockwool sound absorbing board on the ceiling.

Heavy-weight floor impact sound in the state of coupled vibration of floor slab and girder of a pure framed structure

Examples of poor heavy-weight floor impact sound insulation performance of pure framed structures with reinforced concrete were observed relative to the floor slab thickness. To investigate the cause of the poor performance, the floor vibration characteristics of actual pure framed structures were measured during heavy-weight impact. As a result, the floor vibration characteristics of the displacement of girders and the coupled vibration of the girders and floor slabs not seen in conventional floor structures surrounded by girders with reinforced concrete walls were observed. The propagation of the vibration of the floor slab was observed in more than the range surrounded by girders and in the next slab beyond the girders owing to the vibration of the girder itself. It was confirmed that these physical phenomena can be evaluated using a numerical calculation method. The effect of the changes in girder depth on the coupled vibration of the girder and floor slab was also investigated analytically. As a result, the coupled vibration of the girder and floor slab specific to pure framed structures that contribute to heavy-weight floor impact sound insulation performance was clarified physically.

Changes in heavy-weight impact sound isolation by construction stage in new residential buildings

In Korea, 63% of the population lives in residential buildings. Due to the prevalence of residential buildings, there are constant disputes and complaints related to floor impact sound. To address the floor impact sound problems, the Ministry of Land, Infrastructure, and Transport (MOLIT) announced strong legal regulations from 2022. The law holds construction companies liable for compensation if they fail to meet the minimum sound insulation standard. The existing construction methods for floor structures were unable to meet the required minimum sound insulation standards, leading to the need for improvements. The evaluation process was enhanced by changing the source from bang-machine to impact ball, leading to more accurate assessments of floor impact sound insulation. In response to the challenges faced with existing methods, the research paper developed and applied a composite floor structure using a new material with increased area density. The performance of each construction stage in the new composite floor structure was measured and evaluated according to the ISO 16283-2 (testing) and ISO 717-2 (evaluation) standards. The implementation of the new composite floor structure with increased area density resulted in a noise reduction of up to 10 compared to the bare slab. [Work supported by the Industrial Technology Innovation Program (20023556, Development of personalized noise mitigation technology and service based on noise simulation to solve the noise problem in personal space) funded By MOTIE, Korea.]

Effects of Impact Sound Insulation of Floor Covering on the Properties of Wood Organic Resilient Material

近年來樓板緩衝材多以玻璃棉、橡膠墊或發泡類等工業化之產品為主，在製程或回收利用上亦須依賴大量能源之供應。因此，本研究在地球永續與循環經濟之課題下，以栓皮櫟（Quercus suber）樹種作為研究對象，利用木栓層（Cork layer）組織特性，開發木質有機緩衝材，並搭配複合木地板之面材進行樓板衝擊音隔音性能之探討。研究結果顯示，在栓皮櫟樹皮顆粒使用比例為30 %時，衝擊音降低量預估值達22 dB，較10 %及20 %之比例條件佳，且低頻衝擊音降低量數值較常見之橡膠發泡與PU發泡佳，顯示本研究之木質有機緩衝材除符合生態綠建材之原則外，亦可提升建築樓板之隔音性能。In recent years, glass wool, rubber, and foam were the main materials used in floor resilient material, which consume a lot of energy in the process of recycling. Under the topic of earth sustainability and circular economy, in this study, we took Quercus suber as the research object, and use the organizational characteristics of the Cork layer to develop wood organic resilient material. We discussed the floor impact sound insulation performance of laminate wood flooring and wood organic resilient material. The result showed when using 30 % cork oak, the impact sound reduction value of the floor covering was 22 dB. The impact sound insulation performance of low frequencies of wood organic resilient material was better than rubber and foam. The wood-organic resilient material produced in this study was in line with ecological green building materials and improved the sound insulation performance of building floors.

A Study on Floor Impact Sound Insulation Performance of Cross-Laminated Timber (CLT): Focused on Joint Types, Species and Thicknesses

A Study on Floor Impact Sound Insulation Performance of Cross-Laminated Timber (CLT): Focused on Joint Types, Species and Thicknesses

Transfer Matrix approaches for the prediction of impact sound radiation from layered floors

In this work, an efficient and accurate framework for the prediction of the direct impact sound insulation of layered floors is presented. Both floor models of infinite lateral extent and with simply supported boundaries are considered. For the infinite floors, closed-form mechanical admittance expressions are provided which relate directly to the transfer matrix elements of the conventional transfer matrix method (TMM). For floors with simply supported boundaries, an image source argument is employed for underpinning the modal version of the TMM, or mTMM, which approximately accounts for the boundary conditions by considering admissible trace wavenumbers only. It is demonstrated that both for the TMM and the mTMM, the radiated sound power can be evaluated directly in the frequency–wavenumber domain from a simple integral. The accuracy of the mTMM is confirmed in a numerical verification using detailed finite element models. The method is also extensively validated with laboratory measurements for a set of five heavy floors with stiff and resilient layers. A very good agreement between measurements and mTMM predictions is generally observed. The TMM and mTMM approaches yield very similar results above the critical frequency of the base floor, yet at lower frequencies, the inclusion of the finite-size and boundary conditions effects make the mTMM substantially more accurate.

QUESTIONNAIRE SURVEY RESULTS ON CURRENT SOUND INSULATION PERFORMANCE AND SATISFACTION LEVELS IN MULTISTOREY DWELLINGS FOR SALE AND FOR RENT PART 1: CLARIFICATION OF OCCUPANT AND BUILDING ATTRIBUTES AND IDENTIFICATION OF CURRENT ISSUES ON SOUND INSULATION PERFORMANCE

A questionnaire survey was conducted for the clarification of the current state of satisfaction on sound insulation performance in the multistorey dwellings for sale and for rent. The result suggested that the situation was the same with the study completed in 1970s: the floor impact sound insulation performance was one of the most unsatisfied attributes. In addition, tendency of the room type (i.e. 1K or 3LDK), family structures (i.e. single or with kids) and architectural specification (i.e. structure types of the building) on the multistorey dwelling for sale and for rent was different.

Association between hearing threshold and low-frequency walking sounds on concrete floors

The sufficient frequency range to be measured for the rating of impact sound insulation of floors has been a relevant research question since the 1960's when the lower limit of the measured frequency range was set at 100 Hz. It has been long recognized that walking sounds at frequencies lower than 100 Hz might have a significant effect on the experienced impact sound insulation of floors. Recently, it has been suggested that the frequency range to be measured for the rating of impact sound insulation should be enlarged down to 20 Hz. This suggestion is based on studies concerning wooden buildings. It is not known whether such low-frequency walking sounds are generated by walking on concrete floors. The purpose of this preliminary study was to produce sound spectra of several living impact sound sources. The spectra of different sound sources were measured in a laboratory. The results show that, in the case of concrete floors, such low-frequency living sound spectra that would exceed the hearing threshold do not exist, or they are at least uncommon.

Numerical and experimental investigation of the narrow-band impact sound insulation of layered floors

Measurement results of the impact sound insulation of (floating) floors are generally limited to one-third octave bands. As a consequence, detailed information on modal behavior and on the influence of the impact source, are largely lost due to band-integration. To this end, narrow-band measurements are performed on five different layered floors. Various tapping machine locations are considered and the results are averaged over several receiver positions for each tapping machine location in order to reduce the influence of the spatial distribution of the sound pressure in the receiver room. A new prediction model for impact sound transmission, termed the modal TMM, or mTMM, is used to interpret and investigate the measurement results. This prediction method includes a detailed source model and accounts for the finite dimensions of the layered floors. The measurement results of the layered floors clearly indicate the importance of considering all five impact hammer locations of the tapping machine to achieve a high prediction accuracy, especially at low frequencies. The influence of the impact source and the modal behavior of the floor can lead to high peaks in the radiated sound power level.

Effect of concrete topping on floor impact sound insulation performance of CLT floor

The use of wood is being promoted to achieve the goals of the SDGs (Sustainable Development Goals) around the world. In Japan," the Act on Promotion of Utilization of Wood in Buildings" and" Other Structures to Contribute to the Realization of a Decarbonized Society" promotes the use of wood in buildings in general. In addition, CLT (Cross Laminated Timber) is being promoted in order to make effective use of domestic timber. There have been many requests to show wooden structural materials when CLT is adopted to the building (i.e., without ceiling and CLT panel itself is exposed). This paper examined the approach to increase the sound insulation performance of CLT floor without ceiling. The measurement of the floor impact sound insulation performance and driving-point impedance was carried out in the experimental building using concrete floating floor on top of the CLT floor panel with and without floor finishing. As a result, the performance of the concrete floating floor on the CLT floor showed that the performance was almost the same as the concrete floor itself. Moreover, the effect of the floor finishing on the concrete floating floor was investigated.