Kyoung Woo Kim

Analysis of Floor Impact Sound Propagation around the Adjacent Houses

The floor impact sound is a structure-borne sound that is propagated not only to the apartment directly below but also to various other locations. This study identifies how much floor impact sound, which is perceived as a problem for the whole apartment building rather than a problem for just the upper and lower floors, is propagated to surrounding apartments. Further, this study derives various variables for the cause of noise occurring in the apartment building. The measurement results indicate that most of the energy (38–54%) is propagated to the lower floor, which is an apartment directly underneath, for the noise produced when the floor slab is excited. Furthermore, it is found that the noise is propagated simultaneously to the apartments on the upper floor, as well as to the left and right sides.

Characteristic Evaluation of Impact Sound Reduction by Floor Coverings Using Floor Impact Sound in a Test Building

Impact sound reduction under various conditions for a total of eight different types of Floor cosverings currently used in South Korea. The results of floor impact sound within the test building under bare slab conditions indicated a high reduction rate for lightweight impact sound, but poor reduction during heavyweight impact sound testing (Bang Machine, Impact Ball). However, a reduction was identified in the mid-high frequency range (315 Hz–3150 Hz) for the lightweight impact sound, as was a reduction of approximately 2 dB–3 dB at specific frequency ranges, depending on the thickness of the floor coverings, for the heavyweight impact sound on the Ondol structure.

Vibration and Floor Impact Sound Isolation Performance in Bubble Deck Slab

The bubble deck slab has been applied to various buildings due to many advantages including the slab load alleviation and structural stability. The bubble deck slab should not only ensure structural stability but also satisfy the performance standards of floor impact sound required legally to be applied to apartments. This study investigated the characteristics of reduction in vibration and floor impact sound in apartments where the bubble deck slab was applied. The measurement results of vibration characteristics showed that the bubble deck slab had a similar natural frequency with that of the solid slab from a frequency (each of 16.7 Hz and 11.1 Hz) where the first mode was formed but the vibration level of the bubble deck slab at the low frequency band (80 Hz or lower), which was affected by the heavy-weight impact sound, was relatively smaller than that of the solid slab. The bubble deck slab showed a comparable or better performance in the insulation of the floor impact sound compared to that of the solid slab.

Analysis on Correlation among Evaluation Indexes of Heavyweight Impact Sound in Apartment Buildings

Floor impact sound is one noise in apartment houses that cannot be avoided. Heavyweight impact sound can be evaluated by three indexes: a method using reverse-A curve (Li,Fmax,Aw), A-weighted sound level (LiA,Fmax), and the method of the arithmetic mean of measured frequencies (Li,Favg,Fmax). The present study divided slab thickness in apartments into two groups on the basis of 210 mm thickness. Their correlations with the three indexes were then analyzed. Among the three indexes, a determination coefficient (R2=0.97) between the index using reverse-A curve and dB(A) index was the highest. The analysis result of the correlation between the three indexes and frequencies (63 Hz, 125 Hz, 250 Hz) revealed that a correlation with the 63 Hz was the highest although the result was somewhat different depending on data group and index.

Criteria and Characteristics of Elevator Noise in Apartments

Elevator noise in apartments can make annoying sounds depending on locations of elevators and the sensitivity of the residents. Some nations have their own criteria regarding noise from elevators, however, South Korea has no such criteria, which makes it difficult to handle the damage due to noise from elevators. Thus, the present study investigated noise criteria in elevators in other nations and identified the noise characteristics during elevator operation to provide foundational data at the time of setup on noise criteria forelevators. The noise criteria in other nations recommend the maximum noise level to be below NC-20–30 and 25–30 dB(A). The noise measurement in elevators showed that the maximum noise level at the adjacent room was NC-29, 31.4 dB(A) in A Apartment, and NC-26~29, 30.8–32.7 dB(A) in B Apartment.

Investigation of Ways to Reduce Road Traffic Noise of Apartment Complexes Using Computer Simulation

In the present study, computer simulations were carried out using Sound Plan in order to investigate whether road traffic noise levels in two apartment complexes were less than the outdoor noise criteria [65 dB(A)] The sound isolation tunnel was found to be most effective way for noise reduction in the two apartment complexes, although they each have different building arrangements and road traffic. A noise barrier with a height of more than 12 m was required to meet the outdoor noise criteria in apartment complex A. The continuous noise barrier with a height of more than 10 m and enough distance from the road traffic were required in apartment complex B.

Evaluation of Reduction Performance of Floor Impact Sound on Floor Covering in the Reverberation Chamber

In order to reduce floor impact sound in apartment houses, 30 types of floor coverings were chosen to evaluate a performance of reduction in impact sound in the reverberation chamber. In the test of performance of reduction in impact sound using bang machine, a performance of impact sound reduction can be ensured at a low frequency band of 63 Hz and 100 Hz. However, impact sound was amplified at a band of 80 Hz and 125 Hz except for some floor coverings. In the test of performance of reduction in impact sound using a rubber ball drop at a height of 100 cm, a performance of reduction in impact sound was improved from a band of 50 Hz up to 400 Hz. In the test of rubber ball drop at a height of 40 cm, which was similar to the impact of childrens running, a performance of reduction in impact sound was improved from a band of 80 Hz and 160 Hz up to 400 Hz.

Study on Noise Characteristics of Facility Equipment and Subjective Responses

For a house to maintain the standards of a quiet residential environment, it is necessary to reduce not only inter-floor noise delivered from neighboring houses but internal noise sources as well. Currently, noise measures on facility and equipment have been established in apartment houses in South Korea. This study aimed to provide foundational data needed to provide institutional standards on facility noise in apartments. Thus, this study analyzed noise level and acoustical parameters (loudness, sharpness, and roughness) with regard to noises from hoods and boilers in kitchens. This study also studied an annoyance rating, which was a subjective response to the noise, using 36 subjects. It also quantified a subjective response by calculating a %HA (percentage of highly annoyed) according to the maximum noise level from a boiler and kitchen hood, and a mean value of annoyance. No significant difference between the two rating scales was found.

Effect of Changes in Temperature on Resilient Materials Dynamic Stiffness and Floor Impact Sound

Floor impact sound is one noise in apartment houses that cannot be avoided. In order to reduce floor impact sound, a floating floor system using resilient materials has been generally applied. Floor impact sound insulation performance of the floating floor system is dependent on the physical property (dynamic stiffness) of resilient materials. This study investigated the effect of temperature changes on resilient materials used in the floating floor system and on dynamic stiffness. Ethylene vinyl acetate (EVA) and expanded polystyrene (EPS) were used as resilient materials, and dynamic stiffness was measured during three stages of temperature change condition. The measurement result showed that as the temperature decreased, dynamic stiffness also increased. This study also analyzed the effect of changes in outdoor temperature on the heavyweight impact sound level with respect to concrete buildings with wall slabs. The floor impact sound level tended to increase during the winter season, when the outdoor temperature was low.

Changes in Floor Impact Sound Insulation Performance with Time

Floating floor structures installed with resilient materials are commonly used to reduce sound from floor impacts. Resilient materials minimize the transmission of vibrations by absorbing shock vibrations occurring on the upper part. The floor impact sound reduction performance of resilient materials is related to the dynamic stiffness, which is a physical characteristic of materials. However, the dynamic stiffness varies according to the increase in the loading time of the load that is installed on the upper part of resilient materials. The dynamic stiffness values increase with an increase in the loading time; an increased dynamic stiffness value decreases the vibration reduction effect. The present study focuses on a floor structure installed with resilient materials, and identifies the degree of reduction in floor impact sound insulation performance with the elapse of time. The insulation of sound from lightweight impact sound decreased with the elapse of time, whereas the heavyweight impact sound did not show significant changes.