An Experimental Study of the Sound Insulation Performance and Sound Defect Using Sound Intensity According to the Composition of Balcony Windows

Transcription

1 An Experimental Study of the Sound Insulation Performance and Sound Defect Using Sound Intensity According to the Composition of Balcony Windows Tae Hee Kim 1.a, Il Kyung Kang 1.b, Ho Kyoo Jo 1.c 1 Institute of Technology and Quality Development, Hyundai E&C, Yongin, Korea, a taeheekim@hdec.co.kr, b ikkang@hdec.co.kr, c hkcho@hdec.co.kr ABSTRACT According to the statistics of housing construction in Korea, more than 78% of housing is apartment. Apartment housing is usually located near road because of ease accessibility for public transportation. Therefore it is continuously causing complaints from traffic noise and outdoor environment noise. Mainly, noise transmitted from outdoor is blocked by building facade such outer wall, windows and so on. Especially the existence of the balcony as a neutral zone has an effect on reducing the noise. But, since the expanded balcony is allowed by laws, the deletion of the balcony space results in reducing the sound insulation performance. Accordingly, in order to reduce the noise of interior space, the sound insulation performance of window is very important. In this research, 7 types of windows are investigated by sound insulation performance in reverberant rooms. And sound intensity measurement between reverberant room and anechoic room is performed to find the sound defect area of windows. If the air-tightness of the window profile is assured, the sound insulation performance of the window depends on the composition of windows such as the thickness of the glass and air space between glasses. Actually predicted results are similar to the measured data. The sound defect identification using sound intensity is confirmed in this research. KEYWORDS: Balcony Windows, Sound Insulation Performance, Sound Intensity, Sound Defect 1. INTRODUCTION According to the research on the actual condition of noise by the Ministry of Environment of Korea, the 257 regions of the 25 major cities excess the criterion of the outdoor environmental noise (65dB(A) in day and 55dB(A) at night). While apartment is mainly residential type in Korea, quite a number of people have potential to expose the noise inducing the disturbance of the rest and sleeping. Therefore, At the region for exceeding criterion, the central and local government make certain of installation of soundproof facilities such as noise barrier and legislate the indoor noise limit below 45dB(A) at living room. If apartment is constructed from road at a long distance, the environment noise criterion can be satisfied and soundproof facilities is not necessary. Actually apartment housing is usually located near road because of building site is insufficient and accessibility for public transportation is ease. Accordingly, the occupants of apartment continuously complain traffic noise and outdoor environment noise. In past day, the existence of the balcony as a neutral zone has an effect on reducing the noise. But, since the expanded balcony is allowed by laws, the balcony is amended a living space. The deletion of the balcony space results in reducing the sound insulation performance. Accordingly, in order to reduce the noise of interior space, the sound insulation performance of window is very important. 643

2 This study aims to offer the basic information on development of the window systems that reduce the noise transmission through the windows and to make comfortable indoor environment. 2. MEASUREMENT OVERVIEW In this study, two reverberant rooms are used to measure the sound reduction index of windows. A reverberant room and an anechoic room are used to identify the sound defect parts of the balcony window systems such as double glazed window, triple glazed window and fair glass double window. As shown in Table 1, the specification of the test rooms is described. Sound reduction index( of balcony windows is tested by Korea Industry Standard, International Standard Organization and ASTM(see Figure1 and Figure2). As shown in figure 3, test specimens located between anechoic room(receiving room) and reverberant room(source room) are measured by sound intensity method. Though the test and the analysis by sound intensity method is more complicated than the conventional method, sound intensity method has the many advantages of obtaining highly accurate result, understanding the acoustical characteristic of the specimen and identifying the sound defects. Especially, in this measurement (ISO ), the time and space integrated sound intensity level L IN is measured, and the time and space integrated sound pressure level L P is measured simultaneously. Then calculate the surface pressure-intensity indicator from: F PL = L L [db] (2) P IN If the measured intensity is negative or if F PL is not satisfactory (i.e. if F PL > 10 db for a sound reflecting test specimen, or if F PL > 6 db for a test specimen with a sound absorbing surface in the receiving room), increase or decrease the space between specimen surface and sound intensity probe. So the distance between the microphone and test specimen surface is determined by 30cm. This distance between the evenly divided 104 subareas is the same. Table 1. The classification of test rooms Note 1 st Reverberant room 2 nd Reverberant room Anechoic room Shape pentangular heptahedron pentangular heptahedron hexahedron Volume 340m 3 314m 3 384m 3 Surface area 295m 2 276m 2 320m 2 Use Source room/ Receive room Receive room Receive room Figure1. installed specimen Figure2. Sound intensity measurement The compositions of windows system and test specimen symbols are shown in Table 2 and Table 3. Double glazed window and fair glass double window is widely used in Korea. Triple glazed window is 644

3 developed to improve the sound insulation performance and the condensation problem. The elevation and section of window systems are shown in Figure3 and Figure4. Table2. The composition of window systems Double glazed window Note Tilt & turn Thickness and types of glass(mm) 6mm heat strengthened glass + 12mm airspace + 6mm low-e glass Thickness(mm) (included Frame) 24 Triple glazed window Tilt & turn 6mm low-e glass + 12mm airspace + 6mm plain glass + 12mm airspace + 6mm low-e 42 Fair glass double window Sliding 5mm heat strengthened glass + 12mm airspace + 5mm low-e glass : 22mm (outer window) 5mm Plain glass + 6mm airspace + 5mm Plain glass : 16mm (inner window) Table3. The symbol of test specimens Manufacturer A type of window system Test specimen symbols A Double glazed window A-DGW B Double glazed window B-DGW C Fair glass double window C-FGW Double glazed window C-DGW D Fair glass double window D-FGW Double glazed window D-DGW E Triple glazed window E-TGW (a) Elevation Figure 3. A-Double glazed window (b) Section 645

4 (a) Elevation Figure 4. C-Fair glass double window (b) Section 3. EXPERIMENTAL RESULT 3.1 Sound Reduction Performance (1) Double glazed window and triple glazed window The sound reduction index of 4 types of double glazed windows and a triple glazed window is shown in Figure8. Although it make a little difference between each frequency band, the patterns of sound insulation performance is similar. In general, the sound insulation performance of windows and walls depend on the resonance at low frequency and coincidence effect at high frequency. The lowest mass-air-mass resonance, for normal sound incidence angle is calculated by 1.8ρ c 2 ' 1 0 o m1 + f0 = ' 2π d 1 m m m ' 2 ' 2 ' ' where, m 1 and m 2 are the surface masses of the panels(kg/m 2 ), ρ o (=1.2kg/m 3 ) is the density of the air, c o is the speed of the air and d is the thickness of the cavity(m). Thus, the mass-air-mass resonance frequency can occur typically in the range f 0,,5 f 0 when the cavity is empty. In this test result, the predicted resonance frequency by (2) is around 220Hz. As are shown the Figure 5, the resonance frequency of double glazed windows is shown below 220Hz, but that of triple glazed window is not occurred. And the coincidence frequency of 6mm-thickness-glass is 2200Hz, all double glazed systems and triple glazed Figure 5. Comparison of the sound insulation performance of window occur at 2000Hz(1/3 fair glass double windows octave band centre frequency). (2) 646

5 To some extent, predicted results of double glazed windows are similar to the measured data. Also, the coincidence frequency of 6mm thickness of glass is in accord with that of double and triple glazed windows. (2) Fair glass double window The comparison to the sound insulation performance of 2 types of fair glass double windows is shown in Figure 6. At all measurement frequencies, the sound insulation performance of C-FGW is higher than that of D-FGW. It can be explain in differing to the details of frame and air tightness between test specimens, in spite of the same composition of fair glass double window systems. In case of fair glass double window, it is not found that the coincidence frequency falling sound insulation performance. It is deduced that there is more than 100mm air space between glasses. To improve sound insulation performance of window systems, this is another way to increase the air space. 3.2 Sound Intensity Sound Reduction Index[dB] C-FGW D-FGW Frequency[Hz] Figure6. Comparison of the sound insulation performance of fair glass double windows To distinguish the sound defect of window systems, sound intensity method is used. It is shown to the distribution of sound intensity level at each subarea (see Figure 7). In case of double glazed window, there is the diffraction effect at low frequency. At high frequency, the sound transmitted from glass which occupies considerable area of specimen is higher than that the sound transmitted from the frame. Significantly, 2000Hz frequency band, which is included the natural frequency of the glass, the emitted sound intensity level is the highest. Such radiated sound pattern of triple glazed window is the same as that of double glazed windows Figure 7. The sound intensity measurement result at 2000Hz of B-DGW 647

6 5. CONCLUSIONS The results from the experiment and the analysis are as follows : 1) At each measured frequency, sound insulation performance has the difference between fair glass double windows. It is considered that the low air-tightness and the break caused by differing from the detail of the profile and the break drop sound insulation performance. 2) In case of fair glass double window, the dip decreasing sound reduction index is not appeared. It is inferred that 100mm-thickness-air space between the inner window and the outer window cancels the drop of sound insulation performance at the specified frequencies such as resonance frequency and coincidence frequency. In addition, it improves the sound insulation performance. 3) The sound insulation performance is similar with fair double glazed windows. The predicted results by thickness of glass and air space have some analogy to the measured results. It is concluded sound insulation performance of double glazed window depends on the composition of window, especially thickness and material characteristics of glass. 4) By using the sound intensity method, we can research the sound defect lowering sound insulation performance. While sound leak is transmitted significantly through the glass part in double and triple glazed window, it is not obvious that sound leak is transmitted through any specific area of fair glass double window. In this study, all 7 type of window system commonly used in apartment is measured. For in-depth study and research, hereafter, we plan to measure various performance test (e.g., thermal insulation performance, condensation test) of balcony windows. REFERENCES ISO 140-3:1995 Acoustics-Measurement of sound insulation in buildings and of building element Part 3: Laboratory measurements of airborne sound insulation of building elements ISO :2000 Acoustics-Measurement of sound insulation in buildings and of building elements using sound intensity Part 1 : Laboratory measurements The ministry of environment, Improvement of Sound Insulation Performance in Balcony of High Rise Apartments, pp Kim,T.H., Shin,I.S., Cho, C.G., and Sohn,J.Y., Sound insulation performance of lightweight wall panels, soundproof doors and windows in a mockup of broadcasting studio, the proceeding of Architectural Institute of Korea, v.21 n.2( ), pp Hongisto,V., Lindgren,M., and Helenius,R., Sound insulation of double walls-an experimental parametric study, Acta Acoustics United with Acustica, Vol.88(2002), pp Fahy, F.J., Sound intensity, E&FN SPON, 1995, pp