COMPARISON OF SOUND INSULATION PERFORMANCE ON TWO ... · system or hollo-core slab system. It is...

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International Journal of Mechanical Engineering and Technology (IJMET)

Volume 9, Issue 5, May 2018, pp. 612–623, Article ID: IJMET_09_05_067

Available online at http://www.iaeme.com/ijmet/issues.asp?JType=IJMET&VType=9&IType=5

ISSN Print: 0976-6340 and ISSN Online: 0976-6359

© IAEME Publication Scopus Indexed

COMPARISON OF SOUND INSULATION

PERFORMANCE ON TWO DIFFERENT TYPES

OF VOIDED SLAB SYSTEMS

Inkwan Paik and Seunguk Na

Architectural Engineering Department, College of Architecture,

Dankook University, South Korea

Sung-Ho Yun

Kwangjang Structure Co., LTD., South Korea

ABSTRACT

There are several merits of a voided slab system such as economic efficiency,

usability, and environmental friendliness. In particular, it has been proven that a

voided slab system is beneficial in lowering the noise propagation and noise

complaints between floors in apartment housings. One of the most commonly

generated noise issues amongst residents in apartments in South Korea is the

interlayer noise propagation complaints between upstairs and downstairs neighbours.

As a result, it has been gradually more studies focused on solutions for reducing the

interlayer noise problems in apartment housings. In this research, the sound

insulation performances of two types of voided slab systems were tested. Floor impact

sound would generate interlayer noises and it would generate uncomfortable living

environment in apartment housings. The test results of VDS and the post tension

applied voided slab system were completely satisfactory of the minimum requirements

of heavyweight floor impact sound insulation. On the other hand, the lightweight floor

impact insulation performance for VDS was attained grade 1, while the post tension

applied voided slab system was over grade 4. Comparing with the test results of both

voided slab systems, the existence of floor insulator would have an influence on the

propagation of lightweight floor impact sound in the voided slab systems. Comparing

between VDS and the post tension applied voided slab system, VDS showed superb

performance over the post tension applied voided slab system. For the heavyweight

floor impact sound insulation, both voided slab systems reached similar level of floor

impact sound insulation performance. However, the lightweight floor impact sound

insulation performance for the VDS was superior to the post tension method applied

voided slab system. The reason for this result is considered that the installation of

insulator might have a significant element for lightweight floor impact sound

insulation.

T.Tirumala Sandeep, K.Mani bhushan, A.Lalith Sai Kumar, P.Satish kumar and A.Sai Ram Prasad


Key words: Voided slab systems, sound insulation performance, heavyweight floor

impact noise, lightweight floor impact noise

Cite this Article: Inkwan Paik and Seunguk Na and Sung-Ho Yun, Comparison of

Sound Insulation Performance on Two Different Types of Voided Slab Systems,

International Journal of Mechanical Engineering and Technology, 9(5), 2018,

pp. 612–623.

http://www.iaeme.com/IJMET/issues.asp?JType=IJMET&VType=9&IType=5

1. INTRODUCTION

There are a number of studies and approaches have been proposed to satisfy requirements of

large-sized and long-span structures in recent years [1-4]. One of the effective methods to

enhance the capability of long-span and large-scaled structures or buildings is a voided slab

system or hollo-core slab system. It is one of the newly proposed construction methods to

improve the load resistance by effectively utilising the moment of inertia in a concrete slab.

There are several merits of a voided slab system such as economic efficiency, usability, and

environmental friendliness[4-8]. On the other hand, it also has disadvantages that construction

difficulties of voided slabs systems on site are higher than normal reinforced concreted slabs

despite the quantity of concrete and reinforcing bars is reduced. Additionally, extra

construction costs would be incurred for the economic aspect, when the voided slab part is not

properly installed or skilled workers would not work for the installation[1, 3, 9, 10].

In South Korea, there are several examples to install voided slab systems to commercial

buildings and warehouses. Moreover, the systems have since been gradually applied to long-

span structures and large-sized buildings such as underground parking structures, office

buildings, and religious facilities. In recent years, it is being researched the usability and

compatibility of the voided slab systems to apartment housings, which occupies the majority

of domestic dwelling types in South Korea, for solving social issues such as noise complaints

and floor impact noises caused by footsteps[3, 7, 11-15].

As mentioned, a voided slab system has an advantage of serviceability which would be

useful for apartment dwellings. In particular, it has been proven that a voided slab system is

beneficial in lowering the noise propagation and noise complaints between floors in apartment

housings in Japan. Noise insulation from indoor and outdoor-generated noises in apartment

housings is a significant factor in improving the quality of life and comfort of residents. One

of the most commonly generated noise issues amongst residents in apartments in South Korea

is the interlayer noise propagation complaints between upstairs and downstairs neighbours. As

a result, it has been gradually more studies focused on solutions for reducing the interlayer

noise problems in apartment housings[2, 5, 10, 11, 16].

To reduce the interlayer noise matters, it is necessary to evaluate the level of impact sound

insulation performance from slabs. It has been reported that voided formers used in voided

slab systems have an excellent performance for sound insulation against floor impact sound.

In this study, two types of voided slab systems are evaluated and compared the sound

insulation performance for the countermeasure of interlayer noise problems.

2. LITERATURE REVIEW

Voided slab or hollow core slab systems have been used for many years in the field of civil

engineering in South Korea when long span structures such as bridges and dams are

frequently constructed. However, the application of voided slab systems in the architecture,

engineering and construction (AEC) industry occurred later in South Korea than in Europe or

Japan. Although it is later than other countries, the design and application of voided slab

Design and Optimization of Geometrical Characteristics of Helical Spring Using Fusion 360


systems are now being carried out in the construction of various long-span structures and

large facilities.

Research of voided slab systems conducted in South Korea has focused on developing

anchoring methods and devices to anchor void formers to reinforcing bars in concrete slab. In

addition, variety of studies have suggested the use of new void formers to meet both optimum

void ratio and structural capacity [7, 11, 17]. Most of studies regarding anchoring materials

are the use of reinforcing bars which fix the anchoring materials to the lower reinforcement of

the slab. The use of anchoring materials would prevent buoyancy which occurs during the

placement and curing of concrete as well as the movement of void formers by workers during

reinforcement works.

Another research theme of the voided slabs could be categrised into the development of

new shapes of void formers. Since void formers distribute stress depending upon the shape of

them, it is important to design the optimal void formers with appropriate hollowness ratio.

Chung et al. [16] analysed various shapes of void formers and suggested spherical shapes of

void formers for optimal hollowness with structural performance. Joo et al. [3] applied deck

plates to the voided slab system as a means of an anchoring material. They indicated that the

utilisation of deck plates would produce both excellent structural and fixing performance in

the concrete slab. While various researchers have studied the anchoring void formers with the

concrete slabs, various researchers have investigated the structural stability of the voided slabs

which would be vulnerable to shear force since the effective cross-sectional area is reduced.

Research of voided slab systems in South Korea is summarised in Table 1.

Table 1 Studies on the voided slabs in South Korea

Author Year Title

Chung et al. [17] 2013 Experimental study on the bond characteristics of

deformed bar embedded in donut type biaxial hollow slab

Lee et al. [13] 2011 Experimental evaluation on punching shear of two-way

void slab-to-column connection with TVS lightweight ball

Joo et al. [3] 2011 Structural performance test on installation method of void

former for void slab using deck plate

Chung et al. [16] 2009 An analytical study of hollow slabs with optimal hollow

spherical shapes

The development of voided slab systems in South Korea has rapidly increased since the

mid of 2000s. In particular, a voided slab system has been proven that it would significantly

reduce the interlayer and impact noises occurring in apartment dwellings. In addition, a

considerable amount of research on the voided slab systems has been carried out in Europe

and Japan since the 1900s [18-20]. The main research themes conducted in Europe and Japan

have been similar to the topics in South Korea, which are the development of anchoring

materials and fining the optimal hollowness ratio for the structural performance. BubbleDeck

Technology in Denmark and Cobiax Technologies AG in Switzerland have developed a

voided slab system that reduces the amount of concrete required by applying spherical or

elliptical plastic balls as lightweight void formers into one- and two-way slabs [21, 22].

Cobiax AG developed cages for fixing spherical or elliptical shaped void formers to

reinforcing bars to slabs [22].

In Japan, voided slab systems have been widely used in apartment houses in order to

reduce the interlayer noises. As a Japanese study, Sekisui Plastics Co., Ltd., focused on the

development of voided slabs using half precast concrete in the 1980s. The company has been

researching new technologies to prevent the detachment of void formers from slabs in recent



years. Moreover, various other companies in Japan are trying to develop new materials to fix

void former materials to a slab to secure their reliability and durability.

3. RESEARCH METHODS

3.1. Test materials

In this research, two types of voided slab systems, which are the void deck slab (VDS) system

and voided slab system with combination of post-tension method were used. The VDS system

is a voided slab system that utilises T-shaped deck plates in order to anchor void formers

secure between the deck plates web (See Figure 1). The voided slab system with post-tension

method uses paper tubes for void former materials which would be able to materialise long-

span structures (See Figure 2). Moreover, both methods are environmental friendly since the

use of concrete in the slabs can be lowered by inserting void formers in the slabs.

3.2. Test overview

Evaluating sound insulation performance would be one of the significant factors for residents

in apartment housings to provide more comfortable residential environment. Moreover, an

interlayer noise issue has become one of social issues since apartments are the typical

dwelling type in South Korea. Mock-up tests of the floor impact sound were conducted to

evaluate the sound insulation performance for application to apartment housings.

Table 2 Concrete mix design of the mock-up specimens

Design

strength

(MPa)

W/C

(%)

S/a

(%)

Unit content (kg/m3) Air

content

(%) Water Cement

Fine

aggregate

Coarse

aggregate Admixture

24 49.4 47.5 162 328 882 993 1.64 3.5

The insulation performance of two types of voided slab systems, which are the void deck

slab (VDS) system and voided slab system with combination of post-tension method were

evaluated through mock-up tests. The mock-up test specimens were built in compliance with

the standard apartment housing floor plan in South Korea. The concrete and reinforcing bars

applied to both specimens had a compressive strength of 24 MPa and tensile strength of 400

MPa. The floor of the mock-up specimens was finished with lightweight porous concrete, side

insulation, and finishing mortar, as commonly applied to apartment housings in South Korea

according to the standard floor finishing and structures for interlayer noise prevention. The

only difference between the VDS and the voided slab system with post tension method was

that the VDS system applied floor insulators for the floor finishing works. The properties of

the concrete used in the mock-up test specimens are summaried in Table 2. Additionally, the

floor plan of the test specimens is depicted in Figure 4 ~ 5.

(a) Schematic view of VDS (b) Cross-section view of VDS



Figure 1 Details of the void formers used in VDS

(a) Cross-section view of post tension method

applied voided slab system

(b) Detail of the voide former of post tension

method applied voided slab system

Figure 2 Details of the void formers used in the post tension method applied voided slab

3.3. Test methodology

The sound insulation performance of the standard lightweight impact source and heavy

impact source was tested based on Korea Standard to evaluate the sound insulation

performance of the voided slab systems. The mock-up tests were conducted in accordance

with KS F 2810-1:2001 (Field measurement of impact sound insulation of floors-Part 1:

Method using standard light weight source) [23] and KS F 2810-2:2012 (Field measurement

of impact sound insulation of floors-Part 2: Method using standard heavy impact source) [24].

The frequency range of the lightweight impact sound was 125, 250, 500, 100, and 200 Hz,

and the heavy impact sound frequency was measured using a 1/1 octave band of 63, 125, 250,

and 500 Hz, respectively.

(a) Floor impact noise source (bang machine) (b) Light floor impact noise source

(c) FFT analyser and amplifier (d) Non-directional microphone

Figure 3 Test equipment



(a) Cross-sectional plan

(b) Reinforcement plan

Figure 4 Details of the VDS mock-up specimen

The background noise was measured for each frequency level before obtaining the noise

data to calibrate the effect of the background noise. When the level difference between the

background and measured noise was 6 to 15 dB, the acquired data were compensated through

the following expression.

⁄

The floor impact noise level L of the sound receiving room, which indicates the floor

impact sound isolation performance of the floor structure to be measured, was obtained

according to the formula for each measured frequency.

∑



Here, is the maximum sound pressure level measured at point j, and m represents

the number of measurement points.

In the case of a lightweight impact sound level, the sound absorption area of the receiver

room was corrected through the following equation after the level of the normalised floor

impact sound ( was measured.

Here, is 10 m2, A is equal to

, A is the area of absorption (m

2), V is the volume of

the receiver room, and T is the reverberation time.

3.4. Measurement location of the sound

The floor impact sound was measured 0.75m away from the all, and four points including the

centre of the floor were chosen as the measuring point in the mock-up test specimens.

Microphones were used to gather the lightweight and heavyweight impact sound data at a

height of 1.2m from the floor and at a distance of 0.75m from the wall. Figure X and Y

indicate the floor plan of the mock-up test buildings, sound source and receptions points.

(a) Cross-sectional plan

(b) Reinforcement plan

Figure 5 Details of the post tension method applied voided slab mock-up specimen



Sound source Receiver points

(a) VDS

(b) Post tension method applied voided slab system

Figure 6 Sound source and receiver points

3.5. Method of evaluating the insulation performance for standard lightweight

and heavyweight impact sources

The collected data were examined based on KS F 2863-1:2002 (Rating of floor impact sound

insulation for impact source in buildings and building element – Part 1: Floor impact sound

insulation against standard light impact source) and KS F 2863-2:2007 (Field measurement of

floor impact insulation of buildings – Part 2: Method using standard heavy impact sources)

which uses the inverse a normalised curve (See Figure X).

Figure 7 The inverse a normalised curve

In addition, the rating criteria of the floor noise insulation performance for lightweight and

heavyweight sound sources are indicated in Table X. As shown in Table X, the minimum

requirement for sound insulation of the floor impact noise is 58 dB for lightweight impact

sound and 50 dB for heavyweight sound source.



4. RESULTS OF THE MOCK-UP TESTS

4.1. Sound insulation performance

The test results of light and heavy impact floor sounds insulation are summarised in Table 4

and 5. The test results of lightweight floor impact noise indicate that the single number

quantity of all thee for the VDS was 32, 28, and 29 dB respectively. The single number

quantity for the post tension method applied voided slab system was 66, 67, and 66 dB

respectively. According to the standard level of floor impact sound insulation (see Table 3),

the lightweight floor impact sound insulation performance for the VDS reached grade 1 in all

areas of the mock up specimen. The lightweight floor impact sound insulation performance

for the VDS was completely satisfied the minimum requirements of sound isolation. On the

other hand, the lightweight floor impact sound insolation performance for the voided slab

system with post tension method was over 58 dB which was reached over the grade 4 (see

Table 4). Despite the lightweight floor impact sound insulation performance was over the

minimum requirements, the important aspect for sound insulation in the apartment housings

in South Korea is the heavyweight floor impact sound isolation rather than lightweight floor

impact noises.

Table 3 Standard level of floor impact sound insulation (unit: dB)

Grade

Inverse A normalised floor impact

sound level

(Lightweight floor impact noise)

Inverse A normalised floor impact

sound level

(Heavyweight floor impact noise)

1

2

3

4

Table 4 Lightweight floor impact noise insulation performance

Loc. 125 Hz 250 Hz 500 Hz 1000 Hz 2000 Hz

Single

number

quantity

VDS PTV VDS PTV VDS PTV VDS PTV VDS PTV VDS PTV

1 46.0 58.5 31.9 61.3 30.7 64.0 32.5 65.7 31.6 69.0 32 66

2 46.6 59.0 30.6 61.3 27.5 63.6 26.3 66.3 25.4 69.3 28 67

3 49.1 59.1 33.5 62.2 27.9 63.5 25.6 65.6 25.4 67.9 29 66

In addition, the single number quantity of heavyweight floor impact sound insulation

performance tests for the VDS was measured 44, 45 and 43 dB respectively (see Table 5). All

the test results of the single number quantity of heavyweight floor impact sound insulation for

the voided slab system with post tension was 48 dB (see Table 5). The first two experiments

for the VDS specimen were attained grade 2 and the final test was reached grade 1 in the

mock up tests. For the voided slab system with post tension method, all the tests results were

reached grade 4 which is appropriate to apply this system for heavyweight impact sound

insulation for the apartment housings. The results of heavy floor impact sound insulation for

both voided slab systems in this study were acceptable level. As a result of this study, it is

considered that the application of VDS and post-tension applied voided deck system would be

satisfactory for apartment housings to prevent interlayer noise insulation.



Table 5 Heavyweight floor impact noise insulation performance

Loc. 63 Hz 125 Hz 250 Hz 500 Hz Single number

quantity

VDS PTV VDS PTV VDS PTV VDS PTV VDS PTV

1 74.3 77.3 51.1 61.7 33.0 53.9 28.8 45.7 44 48

2 75.5 76.4 50.0 61.4 31.9 53.8 27.3 48.2 45 48

3 73.7 74.2 52.2 62.9 32.1 54.3 25.9 45.4 43 48

4.2. Comparison of the insulation performance

The test results show that the overall heavyweight and lightweight floor impact sound

insulation performance of VDS is superior to the post tension method applied voided slab

system. According to results of the single number quantity, the sound insulation performance

for heavyweight sound insulation performance of both VDS and the post tension method

applied voided slab system indicate similar level of sound insulation level. However, the

overall heavyweight impact sound insulation performance for VDS showed more excellent

about 6.7 % and 11.6 % at two measurement locations except measurement location 1.

In addition, the sound insulation performance of VDS for the lightweight floor impact

showed more outstanding compared to the post tension method applied voided slab system.

Based on the single number quantity of the lightweight floor impact sound, VDS showed the

noise level of about 30 dB which reached the grade 1 (see Table X). On the other hand, the

tested values of the post tension applied voided slab system marked about 67 dB. According

to the test results, the lightweight floor impact sound insulation performance for VDS seems

approximately twice better than the post tension applied voided slab system.

Analysing the data of sound insulation performance, 30 mm insulator for VDS was

applied before the floor finishing materials were installed. It is considered that the application

of insulator significantly influences the lightweight floor impact sound insulation

performance. However, it seems that the influence of insulators towards heavyweight floor

impact sound was relatively insignificant compared to the heavyweight floor impact sound

insulation performance. Based on the results of this study, both voided slab methods would be

effective to insulate heavyweight floor impact sound which is pointed out as one of the main

causes for the interlayer noises propagation issues. Despite of such an advantageous

heavyweight floor impact sound insulation performance, it is reported that the discomfort and

annoyance in the apartment housings would be caused by continuous exposure of lightweight

floor impact sound. Thus, it is considered that when applying the voided slab systems

suggested in this study for sound insulation in the apartment housings, installation of

insulators before finishing the floors in the apartment housings would be beneficial to insulate

both heavyweight and lightweight floor impact sound.

5. CONCLUSION

In this research, the sound insulation performance of two types of voided slab systems were

tested. Floor impact sound would generate interlayer noises and it would generate

uncomfortable living environment in apartment housings. The test results of VDS and the post

tension applied voided slab system were completely satisfactory of the minimum

requirements of heavyweight floor impact sound insulation. On the other hand, the

lightweight floor impact insulation performance for VDS was attained grade 1, while the post

tension applied voided slab system was over grade 4. Comparing with the test results of both

voided slab systems, the existence of floor insulator would have an influence on the

propagation of lightweight floor impact sound in the voided slab systems.



Comparing between VDS and the post tension applied voided slab system, VDS showed

superb performance over the post tension applied voided slab system. For the heavyweight

floor impact sound insulation, both voided slab systems reached similar level of floor impact

sound insulation performance. However, the lightweight floor impact sound insulation

performance for the VDS was superior to the post tension method applied voided slab system.

The reason for this result is considered that the installation of insulator might have a

significant element for lightweight floor impact sound insulation.

Based on the test results, the floor impact sound insulation of both voided slab systems in

this study satisfy the sound insulation performance and regulations for apartment housings in

South Korea. Considering the results of this research, voided slab systems to be applied in

apartment housings might be a useful countermeasure to reduce disputes and discomfort

caused by interlayer floor noise issues. Therefore, it is expected that the application of VDS

and post tension method applied voided slab systems would be beneficial and useful in

preventing interlayer noise issues in apartment dwelling in South Korea.

ACKNOWLEDGEMENT

"This work was supported by the Technology development Program(C0513195) funded by

the Ministry of SMEs and Startups(MSS, Korea)”

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