PROCEEDINGS of the
23rd International Congress on Acoustics
9 to 13 September 2019 in Aachen, Germany,QÀXHQFHRIVXVSHQGHGFHLOLQJW\SHRIUHVLGHQWLDOEXLOGLQJ
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Hansol Song 1; Jongkwan Ryu 2; Inho Kim 3; Yonghee Kim 4
1,2

Chonnam National University, Korea
3

4

POSCO E&C, Korea

Korea Conformity Laboratories, Korea

ABSTRACT
7KLVVWXG\LQYHVWLJDWHGWKHLQÀXHQFHRIVXVSHQGHGFHLOLQJW\SHRIUHVLGHQWLDOEXLOGLQJRQKHDY\ZHLJKWÀRRULPSDFWVRXQGWKURXJKÀRRULPSDFWVRXQGPHDVXUHPHQWVLQWHVWEXLOGLQJXVLQJrubber ball. In general, gypsum
ERDUGLVVXVSHQGHGXVLQJKDQJHUVIRUWKHFHLOLQJ¿QLVKLQJLQWKH.RUHDQUHVLGHQWLDOEXLOGLQJDQGDLUVSDFH
between slab and the suspended ceiling thus occurs. Three types of the suspended ceiling (perforated, soundabsorbenWDQGUHVRQDWRUFHLOLQJ ZHUHWHVWHGWRH[SORUHUHGXFWLRQRIÀRRULPSDFWVRXQGOHYHOLQFRPSDULVRQZLWKJHQHUDOJ\SVXPERDUG5HVXOWVVKRZHGWKDWWKUHHVXVSHQGHGFHLOLQJVVLJQL¿FDQWO\UHGXFHGE\3 to 4 dB
LQ VLQJOH QXPEHU TXDQWLW\ IRU UDWLQJ KHDY\ZHLJKW ÀRRU impact sound insulation. It was also found that
dominant frequency band of the reduction depended on the suspended ceiling types.
Keywords: Heavyweight floor impact sound, Suspended ceiling, Residential building

1. INTRODUCTION
In KoreaÀRRULPSDFWVRXQGVuch as children's jumping and running sounds, which has dominantsound energy in the low frequency, has been perceived as most irritating noise in apartment building[1,2] and causes social problems such as murder and arson case. Several surveys [3,4] in European
country also reported that the sound insulation in the lightweight as well as heavyweight building is
DQLPSRUWDQWIDFWRUIRUFRPIRUWDEOHOLYLQJHQYLURQPHQW7KLVÀRRULPSDFWQRLVHSUREOHPVLQ.RUHDLV
due to fact that there are too many apartment buildings over 60 % of all housing types, which has
relatively thin slab with 120–150mm thickness. Another reason is that people inside home do not wear
shoes and cause easily footstep noise with their bare feet. Accordingly, Korean government forced tohave legal minimum sODE WKLFNQHVV PP  DQG ÀRDWLQJ ÀRRU IRU DSDUWPHQW EXLOGLQJ ZLWK 5&5HLQIRUFHG &RQFUHWH  VWUXFWXUH VLQFH  6HYHUDO VWXGLHV RQ WKH ÀRDWLQJ ÀRRU ZLWK UHVLOLHQW
PDWHULDOVWRUHGXFHÀRRULPSDFWVRXQGKDYHEHHQFDUULHGRXW[5–12]. +RZHYHUWKHÀRDWLQJÀRor withthe resilient material resonates low-frequency sound below about 100 Hz especially for heavyweightÀoor impact sound in box-frame reinforced concrete structure [5,9]. In addition, the several studies[13–22] have been conducted for acoustical treatments on suspended ceiling panel with air gap understructural slab, which is usually used in Korea as well as the other countries. Previous studies[16,18,21] on the suspended ceiling found that air gap between slab and ceiling panel resonates lowfrequency sound below 150 Hz, which is due to air-spring effect. The degree of sound resonance in
low-frequency ranges varied with air gap thickness [16,18]. It was also reported that the suspended
ceilings have limitation on sound insulation because of the bending resonance frequency [13,14]. To
control the amplification of floor impact sound that occurs when installing ceiling, this study proposed
1shs206203@naver.com
2 jkryu@jnu.ac.kr
3
4

kiminho21@gmail.com
yhkim@kcl.re.kr

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three suspended ceiling types which are perforated ceiling, sound absorbent ceiling, and resonatorceiling. The present study analyzed the reduction performance of floor impact sound by the threesuspended ceilings in comparison with general gypsum board through floor impact sound experiments
in test building using rubber ball.

2. PERFORATED CEILING
2.1 Methods
In the ceiling, the general and perforated gypsum boards both with and without the sound absorbent
sheet (non-woven fabric, thickness: 1 mm) were suspended by timber hangers. The thickness of the
air gap between the slab and the gypsum board was 70 mm and 200 mm in the center and side areasof the coffered part, respectively. The perforated gypsum board (thickness: 12.5 mm and mass per unit
area: 8.7 ~ 9.7 kg/m2 ) consists of several holes of diameter 12 mm, and the percentage of perforated
area was about 13 %. Suspended ceilings were installed below the structural slab. The perforated
gypsum board with absorbent sheet attached under the gypsum board was constructed. The
hHDY\ZHLJKWÀRRULPSDFWVRXQGPHDVXUHPHQWVZHUHFDUULHGRXW for ceiling panel with perforated panel(absorbent sheet 1 mm + perforated gypsum board 12.5 mm). The measurement was also made for not
only ceiling with general gypsum board (thickness 12.5 mm) but also slab without the suspended
ceiling, and results were compared one another. The floor impact sound measurements were conductedin a test building (structure: box-frame constructed with reinforced concrete, slab thickness: 120 mm,
wall thickness: 150 mm, floor area: 3.5 × 5.8 m2, height: 2.6 m) for the cases of both with suspended
ceiling. The measurements were based on the standardized methods [23,24], such as using a rubberball for heavy-weight impact source. The impact source and the microphone was placed at the center
position and four corners, totaling five positions. The microphones were located at a height of 1.2 mfrom the floor and at 0.75 m from wall. In the case of heavyweight floor impact sound, the maximum
impact SPL (L i,Fmax), which is the maximum SPLs measured by the fast time constant, was measured.
The single number quantity (SNQ) for impact sound insulation rating (rubber ball: L'i,Fmax, AW ) was
also calculated according to the procedure for evaluating SNQ in the standardized methods [25]. All
the measurements were made for the conditions of no finishing material above the structural slab, andno finishing material over the walls and floors of the receiving room.
2.2 Results
Figure 1 (left) VKRZV ÀRRU LPSDFW VRXQG SUHVVXUH OHYHO (Li,Fmax) in 1/1octave band and SNQ(L'i,Fmax, AW) by rubber ball for gypsum board and sound absorbent ceiling. The 1/1 octave band analysis
was used to calculate the SNQ and compare easily with results of specimen. As shown in Figure 1, floor
impact sound by rubber ball exhibits a dominant low frequency component, and no significant differencein SPL was observed for 32 Hz and 63 Hz octave bands, but in the 125, 250, and 500 Hz band, L i,Fmax

Figure 1 – Floor impact sound pressure level (Li,Fmax) (left) and iPSURYHPHQWLQÀRRULPSDFWVRXQGpressurelevel by installing the suspended ceiling (right) for perforated ceiling

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of perforated ceiling are lower than those of gypsum board. The SNQ of perforated ceiling by rubberball is 3 dB lower than gypsum board. Figure 1 (right) VKRZVWKHLPSURYHPHQWLQÀRRULPSDFWVRXQG
pressure level (L i,Fmax) by installing the suspended ceiling. Gypsum board ceiling showed theamplification of sound in 32 Hz, 63 Hz, and 250 Hz octave band in comparison with case without
ceiling. These amplification were reduced in the case of perforated ceiling. Perforated ceilingexhibited the maximum reduction of 5 dB in the 250 Hz band compared with the gypsum board ceiling.

3. SOUND ABSORBENT CEILING
3.1 Methods+HDY\ZHLJKWÀRRULPSDFWVRXQGPHDVXUHPHQWVZHUHalso carried out in a test building for soundadsorbent ceiling panel (absorbent gypsum board 15 mm with mass per unit area of 10 kg/m2 + 25
mm glass wool with 24 kg/m3 ). The NRC (Noise Reduction Coefficient) of the absorbent gypsum
board is 0.21. The measurement was also made for not only ceiling with general gypsum board(thickness 9.5 mm) but also slab without the suspended ceiling, and results were compared one another.
Figure 2 shows installation of the sound adsorbent ceiling panel in the test building. Sound absorbent
ceiling panel were respectively suspended using steel hanger, carrying channel and T-bar with 60 mm
air gap between structural slab and ceiling. The test building is a box type RC structure with 180 mm
thick concrete slabs, 150 mm thick concrete walls (three sides), and a window (one side). Additionally,a room of the test building has an area of 24.9 m2 (4.7 m × 5.3 m) and a height of 2.7 m. Heavyweightfloor impact sound measurements were conducted using a rubber ball. There were five impact andsound receiving points including the center position. Microphones were positioned at the center andfour corners at height of 1.2 m above floor. The 1/1 octave band analysis and calculation of a SNQ(L'i,Fmax, AW ) were conducted according to KS F 2863-2 [25]Figure 2 – Structure of sound absorbent ceiling (absorbent gypsum board and glass wool)

Figure 3 – Floor impact sound pressure level (Li,Fmax) (left) and iPSURYHPHQWLQÀRRULPSDFWVRXQGSUHVVXUH
level by installing the suspended ceiling (right) for sound absorbent ceiling5149

3.2 Results
Figure 3 VKRZVÀRRULPSDFWVRXQGSUHVVXUHOHYHO (L i,Fmax) in 1/1octave band and SNQ (L'i,Fmax, AW )for gypsum board and sound absorbent ceiling. As shown in Figure 3 (left), L i,Fmax of sound absorbent
ceiling was significantly lower in the octave band over 32 Hz than those of gypsum board. The SNQof sound absorbent ceiling was thus 4 dB lower than gypsum board. Figure 3 (right) shows the
LPSURYHPHQWLQÀRRULPSDFWVRXQGSUHVVXUHOHYHO L i,Fmax) by installing the sound absorbent ceiling.
As shown in Figure 3 (right), it is clearly observed that gypsum board ceiling resonated the sound in
63 Hz band. This resonance was diminished by sound absorbent ceiling, but there was still a resonancein 63 Hz band.

4. RESONATOR CEILING
4.1 Methods+HDY\ZHLJKWÀRRULPSDFWVRXQGPHDVXUHPHQWVZHUHadditionally carried out in a test building forresonator ceiling with resonant panel absorber (hole 50 mm + hole interval 450 mm + air gap 50 mm
with 50 mm glass wool). The measurement was also made for not only ceiling with general gypsum
board (thickness 9.5 mm) but also slab without the suspended ceiling, and results were compared one
another. Figure 4 shows installation of the suspended ceiling with resonant panel absorber in the test
building. Resonant panel absorber was suspended using steel hanger, carrying channel and M-bar with
110 mm air gap between structural slab and ceiling. Resonant panel absorber was connected to M-bar,which is arrayed at every 30 cm using screw. The measurement method is same as section 3.1.

Figure 4 – Structure of the suspended ceiling with resonant panel absorber

Figure 5 – Floor impact sound pressure level (Li,Fmax) (left) and iPSURYHPHQWLQÀRRULPSDFWVRXQGSUHVVXUH
level by installing the suspended ceiling (right) for resonant panel absorber ceiling.

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4.2 Results
Figure 5 VKRZVÀRRU impact sound pressure level (L i,Fmax) in 1/1octave band and SNQ (L'i,Fmax, AW )for gypsum board and resonant panel absorber ceiling. L i,Fmax of ceiling with resonant panel absorberis slightly higher than gypsum board in the 63 Hz band, but in the 125 and 250 Hz band L i,Fmax ofceiling with resonant panel absorber are lower than those of gypsum board. The SNQ of ceiling on
resonant panel absorber is 4 dB lower than gypsum board. As shown in Figure 5, reduced impact
L i,Fmax by resonant panel absorber is most large 6 dB in the 125 Hz band. This result is due to the factthat large absorption coefficient coeᚑFLHQWRIUHVRQDQWSDQHODEVRUEHUZDVVKRZQLQ – 125 Hzband and the ceiling with resonant panel absoUEHUDEVRUEHGKHDY\ZHLJKWÀRRULPSDFWVRXQG Figure
5 (right) VKRZV WKH LPSURYHPHQW LQ ÀRRU LPSDFW VRXQG SUHVVXUH OHYHO L i,Fmax) by installing thesuspended ceiling. As shown in Figure 5, it is observed that resonator absorber resonated the soundin 63 Hz band. In the case of gypsum board, sound below 125 Hz octave band was resonated. The
resonator ceiling showed a 6 dB reduction in the 125 Hz band compared with the regular ceiling.

5. CONCLUSIONS
7KLVVWXG\LQYHVWLJDWHGWKHLQÀXHQFHRIVXVSHQGHGFHLOLQJ type (perforated, sound absorbent, andresonator ceiling) KHDY\ZHLJKWÀRRULPSDFWVRXQGWKURXJKÀRRULPSDFWVRXQGPHDVXUHPHQWVLQWHVW
building using rubber ball. It was found that the three types of suspended ceiling enhance heavyweightfloor impact sound insulation in comparison with normal gypsum board ceiling. The three suspended
FHLOLQJVVLJQL¿FDQWO\UHGXFHGE\3 to 4 dB in SNQ (L'i,Fmax, AW ) IRUUDWLQJKHDY\ZHLJKWÀRRU impact
sound insulation. In addition, the improvement in heavyweight floor impact sound insulation by threesuspended ceilings was found in octave bans over 63 Hz. Especially, perforated and sound absorbent
ceiling slightly reduced the sound resonance, which was found for gypsum board ceiling. Further
research to increase the improvement in heavyweight floor impact sound insulation in 63 Hz octave
band is needed in the future.
ACKNOWLEDGMENT
This research was supported by a grant (16RERP-B082204-03) from Residential Environment
Research Program funded by Ministry of Land, Infrastructure and Transport of Korean government.

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