• 한국소음진동공학회논문집
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• 제27권2호
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• pp.243-250
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• 2017

In this study, single number rating methods of sound absorption coefficients are discussed. After that the sound absorption performance of noise barriers which are classified by Korea Standard are analyzed according to several standards. The existing rating methods such as NRC (noise reduction coefficient), SAA (sound absorption average) or ${\alpha}_w$ (weighted sound absorption coefficient) from ASTM C423, KS F 3505 and ISO 11654 are introduced. The sound absorption performance of noise barrier is evaluated to compare NRC and ${\alpha}_w$ value. When the value is over 0.6 there are large variance between NRC and ${\alpha}_w$ value. As results, it is needed to unify single number rating methods of sound absorption coefficients for Korean standards on sound absorbing materials.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2008년도 춘계학술대회논문집
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• pp.17-20
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• 2008

To develop floor impact sound resilient materials of apartment house effectively, floor impact sound insulation performance test lab. was designed and constructed in T company. Introducing specification and basic performance of this lab. could be helpful in plan and design of another lab. Floor space size of this lab. is $4.2m{\times}5.5m$ and this size is similar with that of living room of usual apartment house's (about $100m^2$) and the height of lab. is 2.4m. Slab thickness is designed by 180mm. Frequency characteristics is similar to general apartment house. Reverberation time of sound receiving room displays 1.26sec in 125Hz by establishing sound-absorbing materials. For light weight impact sound insulation performance of concrete bare floor structure is estimated by $L_{i,AW}\;=\;73$ and for heavy weight is estimated by $L_{i,Fmax,AW}\;=\;50$. Sound pressure level distribution of sound receiving room is ranged very uniformly. With these results, floor impact sound resilient materials could be evaluated and the results could be trusted by comparison tests.

• 한국소음진동공학회논문집
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• 제25권5호
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• pp.345-351
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• 2015

Sounds of electrically powered vehicle components such as window lift system, roller blind, etc., are required to be more comfortable and not to irritate the people emotionally. In this paper, a study was conducted to identify the significant sound quality metric and compose the luxuriousness sound quality index of electrically powered vehicle roller blind which is part of vehicle sunroof system. Before conducting subjective evaluation, sound characteristics of roller blind was analyzed and set the target operating sound for subjective evaluation. Thus, transfer sound of roller blind which has the characteristics of sound modulation was used for subjective evaluation. Multiple linear regression analysis was carried out by chosen Zwicker's metrics which are pointed by comments of jurors. Loudness and sharpness related metrics are prime metrics in luxuriousness sound quality index we composed. Also, effect of roller blind assay when it is attached to real vehicle was identified to evaluate the validity of index.

• 한국소음진동공학회논문집
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• 제18권2호
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• pp.231-237
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• 2008

With the advent of sound field simulator, many sound fields have been reproduced by obtaining the impulse responses of specific acoustic spaces like famous concert hall, opera house. This sound field reproduction has been done by the linear convolution operation between the sound input signal and the impulse response of certain acoustic space. However, the conventional finite impulse response based linear convolution operation always makes real-time implementation of sound field generator impossible due to the large amount of computational burden. This paper introduces the fast convolution method using perceptual redundancy in the processed signals, input audio signal and room impulse response. Temporal and spectral real-time masking blocks are implemented in the proposed convolution structure. It reduces the computational burden of convolution methods for real-time implementation of a sound field generator. The conventional convolutions are compared with the proposed one in views of computational burden and sound quality. In the proposed method, a considerable reduction in the computational burden was realized with acceptable changes in sound quality.

• 한국소음진동공학회논문집
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• 제21권10호
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• pp.883-889
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• 2011

The brand sound of vehicle diesel engine is recently one of the important advantage strategies in the automotive company. Because various noise components masked under high frequency level can be audible in quieter driving situation. Many researches have been carried out for subjective and objective assessments on vehicle sounds and noises. In particular, the interior sound quality has been one of research fields that can give high quality feature to vehicle products. Vehicle interior noise above 500 Hz is usually controlled by sound package parts. The materials and geometries of sound package parts directly affect on this high frequency noise. This paper describes the sound quality evaluation method for the vehicle diesel engine noise to establish objective criteria for sound quality assessment. Considering the sensitivity of human hearing to impulsive sounds such as diesel noise, the human auditory mechanism was simulated by introducing temporal masking in the time domain. Furthermore, each of the human auditory organs was simulated by computer codes, providing reasonable analytical explanations of typical human hearing responses to diesel noise. This method finally provides the sound quality index of vehicle diesel engine noise that includes high frequency intermittent offensive sounds caused by impacting excitations of combustion and piston slap.

• 한국소음진동공학회논문집
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• 제22권11호
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• pp.1137-1143
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• 2012

This paper presents the correlation between psychological and physiological acoustics for the automotive sound. The research purpose of this paper is to evaluate the sound quality of turn-signal sound of a passenger car based EEG signal. The previous method for the objective evaluation of sound quality is to use sound metrics based on psychological acoustics. This method uses not only psychological acoustics but also physiological acoustics. For this work, the sounds of 7 premium passenger cars are recorded and evaluated subjectively by 30 persons. The correlation between this subjective rating and sound metrics is calculated based on psychological acoustics. Finally the correlation between the subjective rating and the EEG signal measured on the brain is also calculated. Throughout these results the new evaluation system for the sound quality on interior sound of a passenger car has been developed based on bio-signal.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2013년도 추계학술대회 논문집
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• pp.525-530
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• 2013

With the increasing the importance of emotional quality of vehicle, the sound quality of systems with electric motor components has become increasingly important. Electric motors are used for windows, seats, sun roof, mirrors, steering columns, windshield wiper, climate control blowers, etc. In this paper, a study was conducted to identify sound quality factors that contribute to customer's satisfaction and preference of the window lift system. Jury test for subjective evaluation was carried out and sound quality index was developed. Averaged sound pressure level and sharpness were significant factors when glass moves down. Also, maximum loudness at stop section and averaged loudness were significant factor when glass moves up. Noise source identification was carried out for the reduced the loudness and sharpness during glass transferred section and impulsive noise at stop section, Using the source identification result, several improvement points were applied. And finally, the degree of sound quality improvement was judged using sound quality index.

• 한국소음진동공학회논문집
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• 제16권6호
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• pp.593-601
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• 2006

In many fire emergencies, the auditory fire alarm signals are very important to save the occupant's life. But as the sound insulation of building elements has been improved, it is more difficult for occupant to recognize the fire alarm signals when the audible fire alarm worked. This is the first study to show the sound attenuation of audible fire alarm device in apartments. We measured and analyzed the sound attenuation level in seven units. The result showed that it was not sufficient to detect the sound from the fire alarm device in bedrooms. Whether the fire alarm device worked or not, the differences of sound level in bedrooms were below 1$\sim$10 dBA. To give the minimum sound level 60 dBA in bedrooms, the proper sound levels from alarm device installed in livingrooms were suggested using computer simulation.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2005년도 추계학술대회논문집
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• pp.620-628
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• 2005

Spatial control of sound is essential to deliver better sound to the listener's position in space. As it can be experienced in many listening environments, the quality of sound can not be manifested over every position in a hall. This motivates us to control sound in a region we select. The primary focus of the developed method has to do with the brightness and contrast of acoustic image in space. In particular, the acoustic brightness control seeks a way to increase loudness of sound over a chosen area, and the contrast control aims to enhance loudness difference between two neighboring regions. This enables us to make two different kinds of zone - the zone of quiet and the zone of loud sound - at the same time. The other perspective of this study is on the direction of sound. It is shown that we can control the direction of perceived sound source by focusing acoustic energy in wavenumber domain. To begin with, the proposed approaches are formulated for pure-tone case. Then the control methods are extended to a more general case, where the excitation signal has broadband spectrum. In order to control the broadband signal in time domain, an inverse filter design problem is defined and solved in frequency domain. Numerical and experimental results obtained in various conditions certainly validate that the acoustic brightness, acoustic contrast, direction of wave front can be manipulated for some finite region in space and time.

• 한국소음진동공학회논문집
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• 제20권10호
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• pp.960-967
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• 2010

The sound field can be classified to the direct, diffract and reverberant sound field. If the sound absorption material in a room is not applied sufficiently, the reverberant sound field increases and the sound pressure in a room also increases when the sound source exists in a room. Therefore, the reverberation time should be controled in order to reduce the reverberant sound as well as sound pressure level in a room. Even though the reverberation time is specified and researched widely in architectural engineering, it is rarely performed in a marine engineering. Therefore, in this research, the reverberation time in a navel vessel is researched related to the noise reduction in a cabin.