scholarly journals Active Cancellation of Higher-Order Blade-Passing Frequency Noise Radiated from a Centrifugal Blower.

2002 ◽  
Vol 68 (671) ◽  
pp. 2056-2063 ◽  
Author(s):  
Yutaka OHTA ◽  
Eisuke OUTA ◽  
Sumio SAITO
Keyword(s):  
Higher Order ◽  
Frequency Noise ◽  
Centrifugal Blower ◽  
Blade Passing Frequency ◽  
Active Cancellation

Noise Reduction of Blade-Passing Frequency Components in a Centrifugal Blower

2004 ◽  
Author(s):  
Yutaka Ohta ◽  
Eisuke Outa
Keyword(s):  
Sound Pressure Level ◽  
Sound Pressure ◽  
Noise Source ◽  
Higher Order ◽  
Pressure Level ◽  
Source Distribution ◽  
Centrifugal Blower ◽  
Blade Passing Frequency ◽  
Active Cancellation ◽  
Frequency Components

A hybrid-type noise control method is applied to fundamental and higher-order blade-passing frequency components, abbreviated to BPF components, radiated from a centrifugal blower. An active cancellation of the BPF noise source is conducted based on a detailed investigation of the noise source distribution by using correlation analysis. The sound pressure level of 2nd- and/or 3rd-order BPF can be reduced by more than 15 decibels and discrete tones almost eliminate from the power spectra of blower-radiated noise. On the other hand, the sound pressure level of the fundamental BPF is difficult to reduce effectively by the active cancellation method because of the large amplitude of the noise source fluctuation. However, the fundamental BPF is largely influenced by the frequency-response characteristics of the noise transmission passage, and is passively reduced by appropriate adjusting of the inlet duct length. Simultaneous reduction of BPF noise, therefore, can be easily made possible by applying passive and active control methods on the fundamental and higher-order BPF noise, respectively. We also discuss the distribution pattern of BPF noise sources by numerical simulation of flow fields around the scroll cutoff.

Evaluation and Prediction of Blade-Passing Frequency Noise Generated by a Centrifugal Blower

1994 ◽  
Author(s):  
Yutaka Ohta ◽  
Elsuke Outa ◽  
Klyohiro Tajima
Keyword(s):  
Frequency Response ◽  
Pressure Fluctuation ◽  
Noise Level ◽  
Noise Source ◽  
Free Field ◽  
Frequency Noise ◽  
Centrifugal Blower ◽  
Density Spectrum ◽  
Blade Passing Frequency ◽  
Field Noise

The blade-passing frequency noise, abbreviated to BPF noise, of low specific speed centrifugal blower is analyzed by separating the frequency-response of the transmission passage and the intensity of the noise source. Frequency-response has previously been evaluated by the authors using a one-dimensional linear wave model, and the results have agreed well with the experimental response in a practical range of the blower speed. In the present study, the intensity of the noise source is estimated by introducing the quasi-steady model of the blade wake impingement on the scroll surface. The effective location of the noise source is determined by analyzing the cross-correlation between measured data of the blower suction noise and pressure fluctuation on the scroll surface. Then, the surface density distribution of a dipole noise source is determined from pressure fluctuation expressed in terms of quasi-steady dynamic pressure of the traveling blade wake. Finally, the free-field noise level is predicted by integrating the density spectrum of the noise source over the effective source area. The sound pressure level of the blower suction noise is easily predicted by multiplying the free-field noise level by the frequency-response characteristics of the noise transmission passage.

Evaluation and Prediction of Blade-Passing Frequency Noise Generated by a Centrifugal Blower

1996 ◽  
Vol 118 (3) ◽  
pp. 597-605 ◽  
Author(s):  
Y. Ohta ◽  
E. Outa ◽  
K. Tajima
Keyword(s):  
Frequency Response ◽  
Pressure Fluctuation ◽  
Noise Level ◽  
Noise Source ◽  
Free Field ◽  
Frequency Noise ◽  
Centrifugal Blower ◽  
Density Spectrum ◽  
Blade Passing Frequency ◽  
Field Noise

The blade-passing frequency noise, abbreviated to BPF noise, of a low-specific-speed centrifugal blower is analyzed by separating the frequency response of the transmission passage and the intensity of the noise source. Frequency response has previously been evaluated by the authors using a one-dimensional linear wave model, and the results have agreed well with the experimental response in a practical range of the blower speed. In the present study, the intensity of the noise source is estimated by introducing the quasi-steady model of the blade wake impingement on the scroll surface. The effective location of the noise source is determined by analyzing the cross-correlation between measured data of the blower suction noise and pressure fluctuation on the scroll surface. Then, the surface density distribution of a dipole noise source is determined from pressure fluctuation expressed in terms of quasi-steady dynamic pressure of the traveling blade wake. Finally, the free-field noise level is predicted by integrating the density spectrum of the noise source over the effective source area. The sound pressure level of the blower suction noise is easily predicted by multiplying the free-field noise level by the frequency-response characteristics of the noise transmission passage.

270 Mechanism of Noise Generation in a Wing Profile Centrifugal Blower : Blade Passing Frequency Noise and Resonance in Casing

2010 ◽  
Vol 2010 (0) ◽  
pp. _270-1_-_270-6_
Author(s):  
Seiji SHIMADA ◽  
Yutaka KURITA ◽  
Yasunori OURA ◽  
Ryohei MORI ◽  
Junji KAMATANI ◽  
...  
Keyword(s):  
Frequency Noise ◽  
Noise Generation ◽  
Centrifugal Blower ◽  
Wing Profile ◽  
Blade Passing Frequency

Active Attenuation of Low Frequency Noise Radiated from Tunnel Exit of High Speed Train

1994 ◽  
Vol 13 (2) ◽  
pp. 39-47
Author(s):  
Min Liang ◽  
Toshiya Kitamura ◽  
Katsushi Matsubayashi ◽  
Toshifumi Kosaka ◽  
Tatsuo Maeda ◽  
...  
Keyword(s):  
Pressure Gradient ◽  
Pressure Wave ◽  
High Speed ◽  
Outer Space ◽  
Low Frequency ◽  
Close Relation ◽  
Frequency Noise ◽  
High Speed Train ◽  
Low Frequency Noise ◽  
Active Cancellation

A pressure wave occurs at the instant when a high speed train enters into a long tunnel. The wave propagates downstream to the tunnel exit and low frequency noise is radiated from the exit to outer space. The low frequency noise causes a lot of problems1 to the residents living near the exit and has a close relation with the pressure gradient of the pressure wave. To attenuate the low frequency noise, an active cancellation system rather than a passive one is developed. This research uses a model tunnel to examine the characteristic of the pressure wave and investigates the possibility to reduce the low frequency noise by reducing the pressure wave gradient with active cancellation.

On Reducing Piping Vibration Levels: Attacking the Source

2002 ◽  
Author(s):  
Zheji Liu ◽  
D. Lee Hill ◽  
Roman Motriuk
Keyword(s):  
Noise Level ◽  
Frequency Noise ◽  
Computational Studies ◽  
Acoustic Liners ◽  
Blade Passing Frequency ◽  
The People ◽  
Acoustic Liner ◽  
Structural Failures ◽  
High Level ◽  
Novel Design

Centrifugal compressors used in the pipeline market generate very strong noise, which is typically dominated by the blade passing frequency and its higher harmonics. The high level noise is not only very disturbing to the people living nearby the installation site but also causes expensive structural failures in the downstream piping. A novel design of Helmholtz array has been developed to address this type of noise problem. Computational studies show that the installation of the Helmholtz array acoustic liner on the compressor diffuser walls is very effective in reducing noise level of the compressor, especially the dominant blade passing frequency noise. The acoustic liner design has been built and tested at an installation site by the customer. The data clearly shows that the use of acoustic liners is indeed very effective in the reduction of both the noise and the vibration levels of the machine.

scholarly journals Influence of Interaction with Tangential Lean Blade and Box Type Casing on Blade Passing Frequency Noise Level in Small Axial-Flow Fans

2011 ◽  
Vol 77 (780) ◽  
pp. 1620-1629 ◽  
Author(s):  
Taku IWASE ◽  
Tetsuya HIOKI ◽  
Yoshihiko KATO ◽  
Taro TANNO ◽  
Osamu SEKIGUCHI ◽  
...  
Keyword(s):  
Noise Level ◽  
Axial Flow ◽  
Frequency Noise ◽  
Blade Passing Frequency
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