• Journal of the Korean Wood Science and Technology
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• 제30권3호
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• pp.75-84
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• 2002

In order to find out impact insulation properties, various types of current radiant floor heating systems and light-framed floors that are used in light-framed residential buildings were evaluated for two types of impact sources at the same time. Sound Pressure Level (SPL) was different from each impact sources for those spectrum patterns and peaks. In case of light-framed floor framework, the excitation position and the assumed effective vibrating area have effects on sound pressure level but it is not considerable, and Normalized SPL was reduced for each frequency by increasing the bending rigidity of joist. The mortar layer in the radiant heating system had relatively high density and high impedance, therefore, it distributed much of the impact power when it was excited, and reduced the Normalized SPL considerably. Nevertheless, Increasing a thickness of mortar layer had little influence on SPL. Ceiling components reduced the sound pressure level about 5~25 dB for each frequency. Namely, it had excellent sound insulation properties in a range from 200 to 4,000 Hz frequency for both heavy and lightweight impact sources. Also, there was a somewhat regular sound insulation pattern for each center frequency. The resilient channel reduced the SPL about 2~11 dB, irrelevant to impact source. Consequently, current radiant floor heating systems which were established in light-framed residential buildings have quite good impact sound insulation properties for both impact sources.

• 한국음향학회지
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• 제27권4호
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• pp.207-214
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• 2008

입체음향을 구현하는 방법으로는 다수의 스피커를 사용하는 다채널 음향재생 시스템과 2개의 스피커나 스테레오 헤드폰을 이용하는 2채널 음향재생 바이노럴 시스템이 있다. 그 중에서 공간 및 비용 상의 문제로 인하여 2채널을 이용한 음향재생시스템이 주목을 받고 있다. 일반적으로 2채널로 입체음향을 재생하기 위해서는 소리가 음원으로부터 청자의 두 귀에 이르는 경로를 모델링한 머리전달함수 (HRTF : Head Related Transfer Function)를 이용하지만 혼돈원추 상에서 음상정위의 혼돈을 주게 되므로 입체감을 저하시킨다는 단점이 있다. 본 논문에서는 2채널 입체음향 시스템을 효과적으로 구현하기 위하여 머리전달함수를 개선하는 알고리즘을 제안한다. HRTF 그룹화 및 심리음향을 이용하여 각 방향에 해당하는 주파수 스펙트럼 특성을 부각시키는 방법을 적용하였으며 시뮬레이션을 통하여 제안한 알고리즘이 정확한 방향감을 생성할 수 있음을 확인하였다.

• 한국수산과학회지
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• 제35권6호
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• pp.563-567
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• 2002

Developing base data on luring fish schools into netting position by the use of underwater audible sound on japanese parrot fish Oplegnathus fasciatus found in the coastal waters of Jeju Island, S. Korea. Auditory threshold was determined by the heartbeat condition technique using pure tones coupled with a delayed electric shock. The audible range of japanese parrot fish extended from 80 Hz to 500 Hz with a peak sensitivity at 200 Hz. The mean auditory thresholds at the frequencies of 80 Hz, 100 Hz, 200 Hz,300 Hz and 500 Hz were 104 dB, 95 dB, 91 dB, 99 dB and 113 dB, respectively. As the frequency became higher than 200 Hz, the auditory threshold increased almost linearly with increasing frequency. Critical ratios of fishes measured in the presence of masking noise in the spectrum level range of 69$\~$78 dB (0 dB re 1$\mu$Pa/$\sqrt{Hz}$) ranged from 21 dB to 40 dB at test frequencies. The noise spectrum level at the start of masking was about 70 dB within the test frequency range. The sound pressure level of 100$\~$200 Hz recognized by japanese parrot fish under the ambient noise is above 91 dB and the critical ratio for them is above 21 dB.

• 한국소음진동공학회논문집
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• 제15권12호
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• pp.1378-1388
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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.

• The Journal of the Acoustical Society of Korea
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• 제20권4E호
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• pp.52-60
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• 2001

This paper describes real time implementation of subband sound localization system on a floating-point DSP TI TMS320C31. The system determines two dimensional location of an active speaker in a closed room environment with real noise presents. The system consists of an two microphone array connected to TI DSP hosted by PC. The implemented sound localization algorithm is Subband CPSP which is an improved version of traditional CPSP (Cross-Power Spectrum Phase) method. The algorithm first split the input speech signal into arbitrary number of subband using subband filter banks and calculate the CPSP in each subband. It then averages out the CPSP results on each subband and compute a source location estimate. The proposed algorithm has an advantage over CPSP such that it minimize the overall estimation error in source location by limiting the specific band dominant noise to that subband. As a result, it makes possible to set up a robust real time sound localization system. For real time simulation, the input speech is captured using two microphone and digitized by the DSP at sampling rate 8192 hz, 16 bit/sample. The source location is then estimated at once per second to satisfy real-time computational constraints. The performance of the proposed system is confirmed by several real time simulation of the speech at a distance of 1m, 2m, 3m with various speech source locations and it shows over 5% accuracy improvement for the source location estimation.

• 대한후두음성언어의학회지
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• 제8권2호
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• pp.161-165
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• 1997

Background : The rhinomanometry and acoustic rhinometry can assess e nasal passage dynamically and statically Recently, analytic methods such as nasometer and sound spectrogram are gaining wide attention to evaluate the nasality objectively. Objectives : firstly to determine if ere was a relationship between the new methods and nasal airway resistance, and secondly to establish if the measurement of nasalance and sound spectrum could be used as an alternative to rhinomanometry and acoustic rhinometry. Materials and Methods : Thirty two patients who underwent either septoplasty and turbinectomy for nasal obstruction were studied. And their ages ranged form 15 to 45 years, with an average of 26.1 years. The rhinomanometry, nasometer, sound spectrogram were performed at preoperative and postoperative 4 weeks day. Results : After operation, subjective symptoms and rhinomanometric results were significantly improved but nasalance and slope of nana, mama and mamma passage had not meningful change. The significnat changes were noted in nasalance and first nasal formant frequency of nasal consonant of velum(angang). Conclusion : Nasometer and sound spectrogram had a limitation for the measure of nasal patency.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2005년도 추계학술대회논문집
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• pp.530-533
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• 2005

Recently, modern reciprocating air compressors tend to be smaller and lighter. But, as the development of performance, they have many problems for noise and vibration. For this reason, many researches are processing for the reduction of noise and vibration by arranging cylinders with V/W type. Especially, noise and vibration problems of reciprocating air compressor cause a rotating unbalance of crankshaft, so it needs a change of crankshaft parameters appropriately. Hence in this study, we changed crankshaft parameters to solve the rotating unbalance and compared results in order to verify the noise and vibration reduction between new and original air compressor. According to modify a crankshaft parameter, the improvements of noise and vibration were showed results of spectrum measured at selected points of the air compressor crankshaft housing and sound intensity contours measured at a belt left side, table that figure out characteristics of noise. Furthermore, we analyzed objective sound quality metrics with recording data of systems. The results showed that, the new design has improved the level of the first harmonic of vibration displacement, noise and objective sound quality metrics.

• 수산해양기술연구
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• 제18권2호
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• pp.71-75
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• 1982

식이음에 대한 어종의 반응행동을 조사하기 위하여 농어, 쥐치, 검복 등의 식이음을 녹음하여 이들의 주파수와 음압준위를 구하고 이들 식이음을 수조에 다시 방성하여 공시어들의 반응행동을 조사한 결과는 다음과 같다. 1) 농어, 쥐치, 검복의 식이음의 주파수범위는 각각 80~350 Hz, 100~300 Hz, 250~500 Hz이고, 음압 준위는 각각 101~108 dB, 102~112 dB이다. 2) 공시어에게 양의 주음반응을 일으키게 하는데는 측정음압보다 20 dB 정도 증가시켜 방성하는 것이 효과적 이였다. 3) 농어는 식이음에 대한 양의 주음반응이 강하나 쥐치와 검복은 약하다. 4) 공시어는 방성 후 5분까지는 양의 주음반응을 나타내나 5분 이후부터는 음의 주음반응으로 변하는 경향이 있다.

• 문화기술의 융합
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• 제8권1호
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• pp.605-609
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• 2022

성인남성이 면도를 하는 것은 생활 필수요건 중에 하나이다. 생리적인 이유로 대부분의 성인 남성들은 수염을 기르고 있으며, 남성들이 수염을 다듬고 잘 관리하면 외모가 더 깔끔해 진다. 습식면도기에 무딘 날을 사용하거나, 적절한 마사지를 사용하지 않으면 피부 자극이 발생하여 면도상처를 입을 수도 있다. 따라서 면도 후 피부가 매끄러워지는 것만큼 면도기의 편리함과 편안함이 필요하다. 본 논문에서는 습식면도가 피부에 주는 자극을 줄이고, 면도의 편리함을 높이기 위한 소리마사지의 사전 면도방법을 제안하였다. 비대면 저주파스피커를 통해 피부를 부드럽게 하거나 유분을 분비해 피부 윤기를 높여서 면도를 부드럽고 안전하게 해 준다. 우리는 습식면도 전후의 피부상태를 파악하기 위해 습식면도 상태의 소리를 각각 녹음하였고, 이 소리스펙트럼으로 그 효과를 객관적으로 비교분석하였다. 즉, 실험결과에서 면도 전 소리마사지가 면도칼과 피부, 피부와 수염 사이의 마찰이 -7.0dB 감소되어 습식면도의 피부상처를 개선하고, 상쾌한 면도가 이루어짐을 알 수 있다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 춘계학술대회논문집
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• pp.887-890
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• 2007

The low frequency noise, including infra-sound is known to affect human physiology and psychology. Guidelines and measurement method of low frequency noise has been introduced in several countries in order to evaluate low frequency noise. In this work, low frequency characteristics of Daejeon subway was investigated in terms of the noise level and spectrum in the interior of running subway car and the subway station. The interior sound pressure level of the passenger car was between 60 and 102 dB in the frequency range of $1{\sim}250$ Hz.