• 제목/요약/키워드: Sound pressure Level

검색결과 690건 처리시간 0.042초

Effect of Suction Nozzle Modification on the Performance and Aero-acoustic Noise of a Vacuum Cleaner

  • Park, Cheol-Woo;Lee, Sang-Ik;Lee, Sang-Joon
    • Journal of Mechanical Science and Technology
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    • 제18권9호
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    • pp.1648-1660
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    • 2004
  • The suction nozzle of a vacuum cleaner was modified to enhance the power performance and to reduce the airflow-induced acoustic noise. The suction power efficiencies of the vacuum cleaner were measured for various nozzles; (1) original nozzle, (2) original nozzle with modified trench height, (3) original nozzle with modified connecting chamber, and (4) a combination of (2) and (3). In addition, the suction pressure and sound pressure level around the suction nozzle were measured to validate the reduction of acoustic noise. The power efficiency and mean suction pressure increased when the trench height of the suction nozzle was increased. This was attributed to the suppression of the flow separation in the suction channel. Modification of the connecting chamber in the original nozzle, which had an abrupt contraction from a rectangular chamber into a circular pipe, into a smooth converging contraction substantially improved the suction flow into the connecting pipe. When both modifications were applied simultaneously, the resulting suction nozzle was more effective from the viewpoints of aerodynamic power increase and sound pressure level reduction.

어구에서 발생되는 소음 -트로올 어구- (UNDERWATER NOISE GENERATED BY FISHING GEAR -Stern trawl net-)

  • 윤갑동
    • 한국수산과학회지
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    • 제12권4호
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    • pp.217-224
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    • 1979
  • 조업중의 어선이나 어구로부터 발생되는 수중소음의 음향특성을 구하기 위하여 특별히 고안된 수중녹음장치를 이용하여 트로올어구의 수중소음을 녹음분석한 결과는 다음과 같다. 1. 조업중인 트로올어구에서 측정수 소음에는 어선이 발하는 소음의 영향을 극히 적다. 2. 소음의 주파수분포는 $DC\~6,300\;Hz$이고 그 중 우세한 주파수대는 $100Hz\~6,300Hz$이며 최대음압은 $137db(re\;1:{\mu}Pa$이었다. 3. 뜸줄부보다 발줄부에서 음압준위가 높고 자루부분에서의 음압준위가 가장 낮았다. 4. 예망중일 때보다 양망중일 때가 음압준위가 높고 투망중의 음압준위가 가장 낮았다. 5. 예망중의 트롤어구에서 발생되는 수중소음의 주된 음원은 어구의 ground rope와 해저의 마찰음 및 otter board와 해저와의 마찰음이라고 추정할 수 있다.

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KRISS 에서 수행된 음향관련 교정 및 시험 검사 동향 (Tendency of Calibration and Test for Acoustic Field in KRISS)

  • 서재갑;정성수;조문재;서상준
    • 한국소음진동공학회:학술대회논문집
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    • 한국소음진동공학회 2000년도 춘계학술대회논문집
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    • pp.1767-1771
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    • 2000
  • We report the number of calibration and test for acoustic field which were conducted in KRISS between the year of 1990 and 1999. The items contain sound level meter and calibrator for calibration and sound absorption coefficient, transmission loss, sound pressure level of siren, sound pressure level and power of acoustic instrument and relative accessories for test. The data show that the number of them have been increased continuously.

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천장 및 벽구성 방법이 바닥충격음 차단성능에 미치는 영향에 관한 연구 (Floor Impact Sound Isolation Performance by Composition of Ceiling and Wall)

  • 김경우;강재식;이승언;양관섭
    • 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.

실 충격원에 대한 바닥마감재 성능 분석 (Performance of floor coverings by impact sound)

  • 정진연;임정빈;이성찬;김경우
    • 한국소음진동공학회:학술대회논문집
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    • 한국소음진동공학회 2014년도 추계학술대회 논문집
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    • pp.419-422
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    • 2014
  • Floor impact sound level is affected by various factors. This study was examined about impact sources and floor coverings influenced at floor impact sound. So this study wishes to get method to reduce sound pressure level of receiving room. Light-weight impact sound in mid frequency and Heavy-weight impact sound in low frequency was affected by floor coverings. Therefore, method to reduce floor impact sound level is to use proper floor coverings. Some coverings can amplify the heavy-weight impact sound in low frequency. Floor impact sound sources used measurement and analysis were standard heavy-impact source(Tapping, Bang, Ball) and living impact sources(Cleaner, Chair, Toy-car, Soccer ball). And Floor coverings used measurements were various thickness vinyl, laminate(or ply-wood) floor. Especially vinyl floor coverings were very effective method to reduce floor impact.

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피스톤 펌핑 위상이 텐덤형 사판식 액셜 피스톤 펌프의 진동, 소음에 미치는 영향에 관한 연구(2) (A Study on Effects of Piston Pumping Phase on Vibration and Noises of Tandem Swash Plate Type Axial Piston Pump(2))

  • 박성환;이진걸
    • 한국정밀공학회지
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    • 제16권12호
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    • pp.31-39
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    • 1999
  • Previous researches and experiments have already verified that the primary noise source of high pressure tandem axial thpe piston pump is fluid-borne noise from the process of oil distribution between the kidney-shaped port and valve plate. So, many researchers have improved pressure gradients and reduced sound levels by applying pre-compression and pre-decompression metering grooves to valve plate. In practice however, the sound level of th high pressure tandem axial type piston pump is still undesirable. This paper testified the effect of pumping phase of the piston on vibration and noise of th high pressure tandem axial type piston pump on the best of theoretical research in $this^(1)$. Therefore considering the pumping phase of the piston when assembling the tandem axial type piston pump, it is possible to reduce 1.5~2[dB]of sound level.

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Numerical Investigation on the Characteristics of Flow-Induced Noise in a Centrifugal Blower

  • Lee, Chanyoung;Jeong, Taebin;Ha, Kyoung-Ku;Kang, Shin-Hyoung
    • International Journal of Fluid Machinery and Systems
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    • 제7권1호
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    • pp.7-15
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    • 2014
  • In the present study, a computational analysis of the flow in a centrifugal blower is carried out to predict a performance and to explain noise characteristics of the blower. Unsteady, 3D Navier-Stokes equations were solved with k-${\varepsilon}$ turbulence model using CFX software. CFD results were compared with the experimental data that is acquired from an experiment conducted with the same blower. The pressure fluctuation in the blower was transformed into the frequency domain by Fourier decomposition to find the relationship between flow behaviors and noise characteristics. Sound pressure level (SPL) which is obtained from wall pressure fluctuation at impeller outlet represents relative overall sound level of the blower well. Sound spectra show that there are some specific peak frequencies at each mass flow rate and it can be explained by flow pattern.

기관의 비정상 배기배출에 의해 생성되는 소음에 관한 연구 (A Study on the Noise Produced by Unsteady Exhaust Efflux of Engine)

  • 이민호;박명규
    • 한국안전학회지
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    • 제12권4호
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    • pp.191-200
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    • 1997
  • This paper discusses prediction of the sound pressure level produced by simple engine exhaust systems(plain pipe, plain expansion chamber pipe, plain expansion chamber with internally extended inlet and outlet pipe, perforated pipe enclosed in a plain expansion chamber) and a computer program has been developed which predicts the sound pressure level and the frequency spectrum. The program utilizes unsteady flow gas dynamic theory and acoustic theory to predict the pressure-time history in the exhaust system and the mass flow rate-time history at the open end of the system and the sound pressure levels(1/3 Octave band levels) and the frequency spectrum in semi-anechoic room. The predictions are compared with measured levels and show a high degree of correlation.

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송풍기의 소음레벨 측정방법 (KS B6361, 2000년 개정내용을 중심으로) (Methods of A-weighted Sound Pressure Level Measurement for Fans and Blowers (KS B 6361, Focus on Revised Content made in 2000))

  • 김경호;이승배
    • 한국소음진동공학회:학술대회논문집
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    • 한국소음진동공학회 2000년도 춘계학술대회논문집
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    • pp.424-432
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    • 2000
  • The revision was provided for the method of A-weighted sound pressure measurement for fans and blowers, in which the newly developed measurement techniques were applied to KS B 6361. This revision includes the sound power methods for radiated sound from the body, the in-duct measurement method, and the correction method for flow noise upon measuring microphone, etc.

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어류의 식이음과 그에 대한 주음반응 -농어.쥐치.검복- (The Spectrum of Feeding Sound and the Response of Seabass, Filefish and Swellfish.)

  • 김동수;윤갑동
    • 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.

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