• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 추계학술대회논문집
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• pp.622-625
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• 2006

This study is a fundamental investigation for standardization of the heavy-weight floor impact measuring method by the impact ball. The distribution chrematistics of floor impact sound level and reverberation time in a receiving room of the testing building for floor impact sound were measured with variations of number and arrangement of the sound-absorbing materials. Total 8 cases were investigated. The distribution of the floor impact sound level($L_{i,\;Fmax}$) was measured at 30 points with same intervals. The absorption coefficient of the room is 0.10 in case of installation of 6 absorbing materials and 0.02 in case of non-installation. The distribution shape of the impact sound pressure level was similar to the result of the bang machine driving at the measured frequency range. However, the overall reduction of the impact sound level investigated in the 125 to 500 Hz shows that the sound absorption characteristics of the receiving room actually affects the result of the heavy-weight impact measurement.

• 한국소음진동공학회논문집
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• 제26권5호
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• pp.578-583
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• 2016

In order to provide a basis data for design of small arms and their silencer, an experimental study on firing noise of small arms was performed around the muzzle of a gun. For this experimental comparison analysis, the target small arms were included most operating small arms in our country. The sound pressure levels were measured at a certain distance which was predetermined according to US army firing test procedure, TOP 3-2-045. By this experimental study, the sound pressure levels of 5.56 mm caliber small arms are 143 dB ~ 145.4 dB and 7.62 mm caliber small arms are 144 dB ~ 145.2 dB. Between the heavy machine gun K12 and M60, the sound pressure level of K12 is slightly lower than M60.Also silencer for K14 snifer rifle was tested. Using this result, it has been found that the reduction effect of the silencer is 15.4 dB but the improvements of silencer performance in the high frequency range have to be studied later on.

• 한국음향학회지
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• 제34권5호
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• pp.351-359
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• 2015

통상의 수중 음향 트랜스듀서는 음압의 크기만 측정할 뿐, 외부에서 들어오는 음향 신호의 방향은 파악할 수 없는 한계가 있다. 이에 본 논문의 저자들은 Tonpilz 트랜스듀서를 바탕으로 단일체로서 음압의 크기와 방향을 동시에 탐지해 낼 수 있는 새로운 벡터 센서구조를 제안하였다. 제안된 구조에는 압전세라믹 링이 4등분되어 있으며, 외부 음압에 대한 각 세라믹 조각의 출력전압을 적절히 조합하면 음원의 방향을 파악할 수 있는 특징을 가진다. 본 논문에서는 이러한 구조를 가지는 Tonpilz 벡터센서를 제작하고 그 특성을 실험적으로 측정하여, 제안된 구조의 타당성을 확인하였다.

• 음성과학
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• 제8권4호
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• pp.139-156
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• 2001

Speech intelligibility in patients with complete dentures is an important clinical problem depending on the material used. The objective of this study was to investigate the speech of two edentulous subjects fitted with a complete maxillary prosthesis made of two different palatal materials: chrome-cobalt alloy and acrylic resin. Three patients with complete dentures in the experiment group and ten people in the controls groups participated in the experiment. CSL, Visi-Pitch were used to measure speech characteristics. The test words consisted of a simple vowel /e/, meaningless three syllabic words containing fricative, affricated and stops sounds, and sustained fricative sounds /s/ and /$\int$/. The analysis speech parameters were vowel and lateral formants, VOT, sound durations, sound pressure level and fricative frequency. Data analysis was conducted by a series of paired T-test. The findings like the following: (1) Vowel formant one of patients with complete denture is higher than that of the control group (p<0.05), while lateral formant three of patients with complete denture is lower than that of the control group (p<0.0l). (2) Patients with complete denture produced lower speech intelligibility with low fricative frequency (/$\int$/) than control group (p<0.0). The speech intelligibility of patients with metal prosthesis was higher than that of those with resin prosthesis (p<0.05). (3) Fricative, lateral and stop sound durations of patients with complete denture were longer than those of the control group (p<0.01 and p<0.05), respectively. Total sound durations of patients with metal prosthesis were similar to that of the control group (p<0.05), while those with resin prosthesis had a shorter duration (p<0.01). This implied that those with metal prosthesis had higher speech intelligibility than those with resin prosthesis. (4) Patients with complete denture had higher sound pressure levels /t/ and /c/ than the control group (p<0.01). However, sound pressure levels for /c/ of patients with metal prosthesis or resin prosthesis was similar to the control group (p<0.05). (5) Patients with complete denture had higher fundamental frequency than the control group (p<0.01).

• 한국정밀공학회지
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• 제22권11호
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• pp.59-63
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• 2005

Since human listening is very sensitive when the sound hit him, the subjective index of sound quality is required. Therefore, at each situation of sound evaluation its composed with the sound quality factor. But, when substituting the level of one frequency band we could not see the tendency of substitution at whole frequency band during the sound quality evaluation. In this study a design of experiment is used. The frequency domain is divided into an equally 12 parts and each level of domain whether is given increase or decrease due to the change of frequency band based on 'sharp' and 'annoy' of the sound quality is analyzed. By using the design of experiment the number of test is reduce very effectively by the number of experiment and each band the main effect will be as a solution. The case of sound quality for 'sharp' and 'annoy' at each band, the change of band (increase or decrease of sound pressure or keep maintain) which will be the most effects on the characteristics of sound quality can be identify and this will be able to us to select the objective frequency band. Through these obtained results the physical changes of level at arbitrary frequency domain sensitivity can be adapted.

• 한국생산제조학회지
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• 제5권2호
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• pp.83-89
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• 1996

The objective of this study is to find experimentally the characteristics of the noise generated by the impinging jet on the normal plate, and also to compare the noise characteristics of the impinging jet with those of the free jet. The experiment is performed for the measurement of the noise specturm, the noise power, and the directivity for the free and impinging jets. From the experiment. it is found that the power of noises generated by the free jet as well as the impinging jet is proportional to the eighth power of the jet velocity through the circular converging nozzle, and that the noise power of the impinging jet is 15dB as high as one of the free jet when the plate distance is about within one to three times the nozzle diameter at the pressure ratio 1.39. The sound pressure level of the impinging jet depends upon the jet pressure and the plate distance. The plate distance with the maximum overall sound pressure level is increased with the jet pressure. The directivities with 1/3 octave band frequency for both the free jet and the impinging jet are greatly influenced by the convection effect.

• 화약ㆍ발파
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• 제23권3호
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• pp.19-25
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• 2005

본 연구에서는 이완식 발파공법과 건교부 제시 발파공법을 적용한 현장에서 지반진동과 소음을 측정, 분석하고 비교하였다. 건교부 방식 발파에 비해 이완식 발파공법이 다소간 진동감쇠 효과가 있었다 발파매트를 사용한 이완식 발파시험 견과가 건교부 방식 발파에 비하여 소음이 감쇠되는 것으로 나타났으며, 파쇄입도는 다소 떨어졌다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 춘계학술대회논문집
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• pp.809-812
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• 2006

This article shows the study on the arresting sound occurrence due to the interaction of the centrifugal Fan and bellmouth suction flow with bellmouth height as variable. It has accomplished to measure of inlet noise and also to analysis suction pressure distribution through experiment and also using CFD. The main cause of sound occurrence was judged with the effect due to static pressure change of bellmouth surface.

• 한국소음진동공학회논문집
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• 제15권4호
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• pp.465-473
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• 2005

The impact sounds, generated by the walking of people, the dropping of an object or the moving of furniture, can be a source of great annoyance in residential buildings. The characteristics and level of this impact noise depends on the object striking the floor, on the basic structure of the floor, and on the finish materials of floor. The focus of this paper is to investigate the amount of improvement impact sound pressure level according to the change of the composition method of ceiling and wall. For this purpose, we tested impact sound pressure level of several cases which is the inserting of mineral wool, the increase of the thickness of air layer, the using of anti-vibration rubber in ceiling and attach the mineral wool on wall in the Floor Impact Sound Test Building of KICT. The results show that the composition method of ceiling and wall is more effective in the reduction of light weight impact sound specially in 125Hz and 250Hz.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2012년도 추계학술대회 논문집
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• pp.75-80
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• 2012

Helmholtz resonator is widely used acoustic instrument which has high absorption characteristics at its resonance frequency. Particularly it maintains good performance even in the low frequency region that is difficult to control by general porous absorptive materials. However, under severely high sound pressure level, the absorption characteristics are changed by increase of resistance due to nonlinear behavior of neck impedance. Because of this nonlinear behavior, it is difficult to obtain the expected absorption performance under high sound pressure environment. Thus, in order to prevent excessive rise of resistance, the resonator with neck having cross section dimension decrease away from the entry of the resonator cavity could be suggested. This paper introduces the experiment method and results about nonlinear characteristics of Helmholtz resonator with tapered neck and proposes the approximate nonlinear impedance model.