A A A Effect of concrete topping on floor impact sound insulation perfor- mance of CLT floor Atsuo Hiramitsu 1 Building Research Institute 1, Tachihara, Tsukuba-City, Ibaraki, 305-0802, Japan Susumu Hirakawa 2 National Institute for Land and Infrastructure Management 1, Tachihara, Tsukuba-City, Ibaraki, 305-0802, Japan ABSTRACT The use of wood is being promoted to achieve the goals of the SDGs 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 is being promoted to make effective use of domestic timber. There have been many requests to show wooden structural materials when CLT is adopted in the building. This paper examined the approach to increase the floor impact sound insulation performance of the CLT floor without ceiling. First, the measurements of the driving-point impedance of test specimens were carried out. Then, the measurements of the floor impact sound insulation performance were carried out in the model build- ing using concrete floating floor or composite floor on the CLT floor panel with and without floor finishing. As a result, the performance of the concrete floating floor or composite 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 floor impact sound insulation performance was investigated. 1. INTRODUCTION The promotion of the utilization of wood contributes to the reduction of CO 2 and achieving the goals of the SDGs (Sustainable Development Goals). In Japan, “ the Act on Promotion of Utilization of Wood in Buildings and Other Structures to Contribute to the Realization of a Decarbonized Society ” was enforced, and a low-rise building is to be positively constructed of wood. CLT (Cross Laminated Timber) is being promoted to make effective use of domestic timber, and CLT has been standardized as a building material by JAS (Japanese Agricultural Standard). The acoustics environment perfor- mance of CLT buildings is lower than that of concrete construction buildings. Hence, it is important to study the acoustics environment performance of wooden CLT buildings 1-8 . This is especially be- cause the floor impact sound insulation performance is affected by the area density and stiffness of the floor structural frame. The floor impact sound insulation performance becomes many problems and troubles in timber construction buildings. 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). However, when the ceiling structure 1 hiramitu@kenken.go.jp 2 hirakawa-s92ta@mlit.go.jp 21-24 AUGUST SCOTTISH EVENT CAMPUS ? 02 ? GLASGOW is not constructed, there is no sound insulation effect by the ceiling structure. This paper examined the approach to increase the floor impact sound insulation performance of the CLT floor without ceilings. 2. FLOOR IMPACT SOUND REDUCTION IN TIMBER CONSTRUCTION BUILDING The basics of floor impact sound insulation measures for timber construction buildings are summa- rized in Table 1. The change in floor impact sound insulation performance can be estimated by the driving-point impedance change in the floor structure shown in Equations 1 and 2. This study focused on "3) Reduction by floor structure" in Table 1. Here, a method of placing concrete on the CLT floor was investigated as a way to increase the weight and stiffness of the floor structure. 𝑍 ൌ8 √𝐵𝑚 (1) (2) 𝐵ൌሺ𝐸𝐼ሻ where, Z b : Driving point impedance (kg/s) B : Bending rigidity of floor section (N/m 2 ) m : area density of floor structure (kg/m 2 ) E : Young's modulus of floor structure (N/m 2 ) I : Secondary moment of the cross-section of floor structure (m 4 ) Tabl e 1: Basics of floor impact noise measures for timber construction building. Basics of Counter- m e asure Examples of Countermeasures Consideration of lay- out planning of sound source room and sound re c eiving room Do not place rooms with large floor impact on the upper floors of rooms that require quiet conditions, etc. 1) 2) Reduction of impact input to the floor with floor finish structure Adoption of a dry-type double floor structure (the floating floor). Restrictions on the movement of people in the room. Prevention of falling objects, etc. Increase weight in the floor structure. Increase in driving-point impedance due to increase in floor rigidity, etc. 3) Reduction by floor structure Installing a ceiling that is vibrationally independent of the floor struc- ture. Insert sound-absorbing material into the ceiling, etc. 4) Insulation with the ceiling 5) Control of the sound receiving room Measures to reduce the vibration transmitted from the floor to the wall. Sound absorption in the sound receiving room, etc. 21-24 AUGUST SCOTTISH EVENT CAMPUS ? 02 ? GLASGOW 3. DRIVING-POINT IMPEDANCE OF CLT WITH CONCRETE TOPPING MEASURE- MENTS The driving-point impedances were measured for two types of specimens; a floating floor and a com- posite floor with concrete on the CLT panel. 3.1. Floating Floor The driving-point impedance measurements were carried out on 210 mm thick CLT panels (7 layers, 2,000 mm x 2,000 mm) for the specimens shown in Table 2. Specimen A0 is a bare CLT panel, specimens A1 and A2 are concrete placed directly on the CLT panel and specimens A3 - A6 are floating floors with a 96K glass wool for vibration isolation layer and the thicknesses of the glass wool and concrete were changed. For the floating floors, polyethylene film was installed under the concrete. The measurements were taken at two positions; near the position of excitation (top surface) and directly below the position of excitation (bottom surface). Table 2 shows the results of the driv- ing-point impedance level. As a result, the response impedance during impact time at the measure- ment position of bottom surface (radiating surface of floor impact sound), the value of specimen A6 is larger. These results indicate that 50 mm thick glass wool and 100 mm thick concrete are effective. Table 2: Outline of section specifications of specimen and measurement results of driving-point im- pedance level in a floating floor. Grass Wool Concrete Driving-point impedance level of top surface [dB] Driving-point impedance level of bottom surface [dB] A0 w/o w/o 95.8 98.5 A1 w/o t = 50 102.9 104.5 A2 w/o t = 100 110.9 111.1 A3 96K, t = 25 t = 50 95.9 121.4 A4 96K, t = 25 x 2 96.1 125.5 A5 96K, t = 25 t = 100 108.0 128.3 A6 96K, t = 25 x 2 107.8 135.9 3.2. Composite Floor Although the results of 3.1 showed that the floating floor is effective in increase floor impact sound insulation, a composite floor consisting of CLT panel and concrete was investigated to ensure the holding ultimate lateral strength. The composite floor was made of CLT and concrete using connect- ors made of steel plates and reinforcing bars. The driving-point impedance measurements were car- ried out on two types of 150 mm thick CLT panels (5 layers, 1,000 mm x 3,000 mm); specimen B1 without any connecters and specimen B2 with connecters installed at four diagonal quarter positions, excluding the center of the specimen. The top surface of the specimen was excitated with an impact hammer at the center of the specimen and the diagonal quarter position (1/4 position) and measure- ments were taken at two positions: near the point of shaking (top surface) and directly below it (bot- tom surface). Table 3 shows the results of the driving-point impedance level. When the connecter was impacted (1/4 position), there was an increase of only approximately 1 dB. 21-24 AUGUST SCOTTISH EVENT CAMPUS ? 02 ? GLASGOW Table 3: Outline of section specifications of specimen and measurement results of driving-point im- pedance level in the composite floor. Driving-point impedance level of bottom surface [dB] Impact position Driving-point impedance level of top surface [dB] B1 Center 109.2 109.3 Diagonal 1/4 position w/o connector 104.0 104.3 B2 Center 109.6 109.8 Diagonal 1/4 position w/ connector 105.4 105.4 4. FLOOR IMPACT SOUND INSULATION PERFORMANCE MEASUREMENTS 4.1. Six-story Wood-frame Model Building The measurements of the floor impact sound insulation performance were carried out in the six-story wood-frame model building 9 . In this model building, earthquake protection, fire resistance, worka- bility, durability, and sound insulation performance, etc. are verified. It is 7,280 mm wide, 5,005 mm deep and 17,309 mm in height. Each of the five floors (1st floor to 5th floor) has almost the same arrangement of living space, and there were two living areas (dwelling units, 3,640 mm wide and 2,502.5 mm deep) on each floor except for the 6th floor. The 6th floor has one living area. The five different separating floors exist on each floor, The 2nd floor is made of 210 mm thick CLT (7 layers), and the floor impact sound insulation performance was measured in one of the rooms on the 2nd floor. 4.2. Measurement Method The floor impact sound insulation performances were measured in conformity with the requirements of JIS A 1418-2: 2019 10 for the heavy-weight floor impact sound insulation and JIS A 1418-1: 2000 11 for the light-weight floor impact sound insulation. The impact sources for measurement of the heavy- weight floor impact sound were a car-tire source (a bang machine) and a rubber ball source, and of the light-weight floor impact sound source was a tapping machine. The impact positions were five positions, and the sound receiving positions were five positions. The floor impact sound insulations were evaluated with JIS A 1419-2: 2000 12 . A-weighted floor impact sound pressure levels by synthe- sis were also calculated; heavy-weight floor impact sound: 31.5 to 500 Hz octave band, light-weight floor impact sound: 125 to 2000 Hz octave band. 4.2. Floor Section Specification Table 4 shows the outline of section specifications of the specimen. Specimen No. 1 was originally constructed with triple-layer 21 mm thick fire-resistant gypsum boards on and bottom surfaces of the CLT floor panel, assuming a 2-hour fireproof construction. Specimens No. 2 and No. 3 were con- structed with a floating floor (the fireproofing layer of the bottom surface was removed for specimen No. 3), specimen No. 4 had the floating floor layer removed, specimen No. 5 had the bare CLT floor, and specimen No. 6 had the composite floor installed. For the composite floor, connectors were in- stalled at six locations. The concrete and the walls were separated by buffer material. Moreover, specimen No. 7 had a dry-type double floor structure on specimen No. 6. The cross-sectional speci- fications of the dry-type double floor structure (finished floor height: approximatly 155 mm) consist of wooden flooring (t=12), asphalt vibration-damping sheets (t=8) and particleboard (t=20) from the finished surface. 21-24 AUGUST SCOTTISH EVENT CAMPUS ? 02 ? GLASGOW Table 4: Outline of section specifications of the specimen. Top surface Bottom surface No.1 Structural plywood, t = 12 Fire-resistant gypsum board, t = 21 x 3 Fire-resistant gypsum board, t = 21 x 3 No.2 Floating floor Concrete, t = 100 Polyethylene film Polyurethane vibration isolation, t = 25 Structural plywood, t = 12 Fire-resistant gypsum board, t = 21 x 3 No.3 No.4 Structural plywood, t = 12 Fire-resistant gypsum board, t = 21 x 3 No.5 w/o w/o No.6 Composite floor Concrete, t = 100 Poly e thylene film Dry-type double floor structure Composite floor Concrete, t = 100 Polyethylene film No.7 4.3. Results and Discussions Figure 1 shows the measurement results of floor impact sound pressure level and Figure 2 shows the calculation results of floor impact sound pressure level difference from No. 5 (CLT bare floor). The performance of specimens No. 1, No. 4 and No. 5, which had not concreted, was low; perfor- mances were L r -70 to 75 of heavy-weight floor impact sound (car-tire source) and L r -90 to 95 of light- weight floor impact sound. The performances of specimens No. 2 and No. 3 with floating floors were high; performances were L r -60 of heavy-weight floor impact sound (car-tire source) and L r -70 light- weight floor impact sound. The amount of effect of the floating floor layer was similar to that of the concrete slab. The 21 mm thick fire-resistant gypsum boards installed on the bottom surface had little effect due to the small change in driving-point impedance, and specimen No. 2 showed dips in the 125 Hz and 500 Hz octave bands that appeared to be a resonance of the fire-resistant gypsum board. The performance of specimen No. 6, a composite floor, was lower than that of the floating floor, L r - 65 of heavy-weight floor impact sound (car-tire source) and L r -95 of light-weight floor impact sound, indicating that the performance was generally that of the cast concrete. After the construction of the dry-type double floor structure, the performances were L r -70 for heavy- weight floor impact sound (car-tire source) and L r -60 for light-weight floor impact sound, indicating that the light-weight floor impact sound insulation performance was improved, but the heavy-weight floor impact sound insulation performance was decreased. In the evaluation of Architectural Institute of Japan grades of the floor impact sound insulation for apartment house 13 , the heavy-weight floor impact sound insulation was outside the grade range of applicable grade and the light-weight floor impact sound insulation was Third Grade. The countermeasures are considered necessary to improve the floor impact sound insulation. 21-24 AUGUST SCOTTISH EVENT CAMPUS ? 02 ? GLASGOW 21-24 AUGUST SCOTTISH EVENT CAMPUS ? 02 ? GLASGOW 110 110 110 100 100 100 90 90 90 Floor impact sound pressure level [dB] Floor impact sound pressure level [dB] Floor impact sound pressure level [dB] 80 80 80 70 70 70 60 60 60 50 50 50 No.1(Lr-num:74, 72.4dBA) No.1(Lr-num:76, 75.0dBA) No.1(Lr-num:94, 92.3dBA) No.2(Lr-num:60, 58.2dBA) No.2(Lr-num:54, 53.4dBA) No.2(Lr-num:72, 69.2dBA) No.3(Lr-num:60, 57.6dBA) No.3(Lr-num:56, 53.2dBA) No.3(Lr-num:69, 67.1dBA) 40 40 40 No.4(Lr-num:72, 71.4dBA) No.4(Lr-num:72, 71.6dBA) No.4(Lr-num:90, 88.8dBA) No.5(Lr-num:75, 73.8dBA) No.5(Lr-num:74, 73.9dBA) No.5(Lr-num:97, 96.4dBA) No.6(Lr-num:66, 62.5dBA) No.6(Lr-num:62, 61.3dBA) No.6(Lr-num:93, 91.4dBA) No.7(Lr-num:68, 68.6dBA) No.7(Lr-num:59, 57.8dBA) No.7(Lr-num:62, 60.9dBA) 30 30 30 31.5 63 125 250 500 31.5 63 125 250 500 125 250 500 1000 2000 Figure 1: Measurement results of floor impact sound pressure level. (left: car-tire source, middle: rubber ball source, right: tapping machine) Octave band center frequency [Hz] Octave band center frequency [Hz] Octave band center frequency [Hz] 60 60 60 No.1 No.1 No.1 Floor impact sound pressure level difference from No. 5 [dB] Floor impact sound pressure level difference from No. 5 [dB] Floor impact sound pressure level difference from No. 5 [dB] No.2 No.2 No.2 No.3 No.3 No.3 50 50 50 No.4 No.4 No.4 No.5 No.5 No.5 No.6 No.6 No.6 40 40 40 No.7 No.7 No.7 30 30 30 20 20 20 10 10 10 0 0 0 -10 -10 -10 31.5 63 125 250 500 31.5 63 125 250 500 125 250 500 1000 2000 Figure 2: Calculation results of floor impact sound pressure level difference from No. 5 (CLT bare floor). (left: car-tire source, middle: rubber ball source, right: tapping machine) Octave band center frequency [Hz] Octave band center frequency [Hz] Octave band center frequency [Hz] Figure 3 shows the results of the reduction of transmitted floor impact sound pressure level of results of dry-type double floor structure to investigate the effect of the dry-type double floor structure on the floor impact sound insulation performance of a composite CLT floor. The positive values in Fig- ure 3 indicate that the construction of the dry-type double floor structure e improved the performance. Although the dry-type double floor structure on the CLT floor contributed to the improvement of heavy-weight floor impact sound insulation performance in the previous reports 3-7 , the performance of heavy-weight floor impact sound insulation performance decreased in this study. The values of the two standard heavy-weight impact sources in the 31.5 Hz and 63 Hz octave bands in Figure 3 were almost the same, while the rubber ball source tended to be larger above the 125 Hz octave band. These results are similar to those for concrete floors such as homogeneous concrete slabs. The performance of the light-weight floor impact sound insulation performance was improved by the installation of the dry-type double floor structure. 60 60 60 Reduction of transmitted floor impact sound pressure level [dB] Reduction of transmitted floor impact sound pressure level [dB] Reduction of transmitted floor impact sound pressure level [dB] 50 50 50 40 40 40 30 30 30 20 20 20 10 10 10 0 0 0 -10 -10 -10 -20 -20 -20 31.5 63 125 250 500 125 250 500 1000 2000 31.5 63 125 250 500 Figure 3: Reduction of transmitted floor impact sound pressure level of the dry-type double floor structure. (left: car-tire source, middle: rubber ball source, right: tapping machine) 5. CONCLUSIONS Octave band center frequency [Hz] Octave band center frequency [Hz] Octave band center frequency [Hz] This paper presents the driving-point impedance and the floor impact sound insulation performance of concrete poured CLT floor without a ceiling structure. As a result, the performance of the concrete floating floor or composite on the CLT floor showed that the performance was almost the same as the concrete floor itself. Moreover, it was shown that the heavy-weight floor impact sound insulation performance of composite CLT floor tends to be reduced by the construction of a dry-type double floor structure. 21-24 AUGUST SCOTTISH EVENT CAMPUS ? 02 ? GLASGOW 6. ACKNOWLEDGEMENTS This CLT model building was constructed under the fund by Ministry of Land, Infrastructure and Transport. This research was conducted as a part of the joint research of the Building Research Insti- tute (BRI) and the Japan CLT Association. 7. REFERENCES 1. Zeitler, B., Schoenwald, S., Sabourin, I. Direct impact sound insulation of cross laminate timber floors with and without topping. Proceedings of INTER-NOISE 14 , Melbourne, Australia, No- vember2014. 2. Hiramitsu, A., Harada, K., Noji, K. Improvement of Sound Insulation Performance of Cross Lam- inated Timber Separation Wall. Proceedings of International Western Pacific Acoustics Confer- ence 2015 , Singapore, Singapore, December2015. 3. Hiramitsu, A., Harada, K., Noji, K. Effect of difference in specification on sound insulation in cross laminated timber separation wall. Proceedings of International Congress on Acoustics 2016 , Buenos Aires, Argentine, September2016. 4. Hiramitsu, A., Otsuru, T., Tomiku, R., Harada, K. Improvement of floor impact sound insulation in cross laminated timber model building for experiment. Proceedings of INTER-NOISE 16 , Ham- burg, Germany, August2016. 5. Hiramitsu, A., Hirota, T., Miyauchi, J., Uematsu, T., Nabeta, Y. Experimental study on floor impact sound insulation and vibration characteristics in cross laminated timber building. Proceed- ings of INTER-NOISE 17 , Hong Kong, Hong Kong, August2017. 6. Hiramitsu, A., Tsuchimoto, T., Kurumada, S. Floor impact sound insulation and airborne sound insulation on CLT model building. Proceedings of INTER-NOISE 18 ; Chicago, USA, Aug- sut2018. 7. Hiramitsu, A., Tsuchimoto, T., Kurumada, S. Influence of floor finish structure on floor impact sound insulation in CLT model building. Proceedings of INTER-NOISE 19 ; Madrid, Spain, June2019. 8. Hiramitsu, A., Hirakawa, S., Tsuchimoto, T., Yamauchi, T. Effect of different types of ceilings on floor impact sound insulation performance in CLT model building. Proceedings of INTER- NOISE 21 ; Washington, America, August2021. 9. Hiramitsu, A., Tomita, R., Hirakawa, S., Sato, M. K. Floor impact sound insulation of the six- story wood-frame model building. Proceedings of International Congress on Acoustics 2019 , Aachen, Germany, September2019. 10. Acoustics – Measurement of floor impact sound insulation of buildings – Part 2: Method using standard heavy impact sources, Japanese Industrial Standard JIS A 1418-2: 2019, Japanese In- dustrial Standards Committee, 2019. 11. Acoustics – Measurement of floor impact sound insulation of buildings – Part 1: Method using standard light impact source, Japanese Industrial Standard JIS A 1418-1: 2000, Japanese Indus- trial Standards Committee, 2000. 12. Acoustics – Rating of sound insulation in buildings and of building elements – Part 2: Floor im- pact sound insulation, Japanese Industrial Standard JIS A 1419-2: 2000, Japanese Industrial Standards Committee, 2000. 13. Architectural Institute of Japan, Floor Impact Prevention Design of Building, Tokyo, Gihodo Shuppan, 2009. 21-24 AUGUST SCOTTISH EVENT CAMPUS ? 02 ? GLASGOW Previous Paper 247 of 769 Next