Active Cancellation of Sound in a Submerged Pipe

1995 ◽  
Author(s):  
Kam W. Ng
Keyword(s):  
Noise Reduction ◽  
Active Control ◽  
Phase 1 ◽  
Active Noise Control ◽  
Jet Noise ◽  
Preliminary Test ◽  
Dipole Source ◽  
Two Phase ◽  
Measurement Capability ◽  
Hybrid Controller

Abstract Active noise control (ANC) technique was demonstrated to reduce fluidborne noise in a submerged pipe. Specifically, the technique was applied to the flow-induced noise caused by a confined jet under both steady-state and transient conditions. A hybrid controller, which combined both feedforward and feedbackward control, was used to speed up the response of the ANC system. A preliminary test was conducted in air to test the hybrid controller with simulated confined jet. A 10-dB reduction was observed for broadband jet noise. To quantify the noise reduction potential of the ANC system in water, a two-phase test program was demonstrated. Phase 1 testing focused on the design and development of the controller and optimized the overall ANC system performance; the test was conducted in an acoustic tank. Phase 2, the actual test and evaluation of the ANC system for the submerged pipe with confined jet noise, was conducted in a lake with underwater acoustic measurement capability. Nearfield and farfield noise measurements, including directivity patterns, were obtained for a confined jet with and without active control. Without active control, the submerged pipe directivity depicted a two-lobe pattern similar to a dipole source. With active control, a 10-dB noise reduction was observed in the pipe downstream direction, whereas in the upstream direction the noise level remained the same.

Semi-active control of smart porous structure for sound absorption enhancement

2019 ◽  
Vol 30 (17) ◽  
pp. 2575-2580
Author(s):  
Bo-Seung Kim ◽  
Semin Kwon ◽  
Seongyoung Jeong ◽  
Junhong Park
Keyword(s):  
Porous Medium ◽  
Noise Reduction ◽  
Active Control ◽  
Sound Absorption ◽  
Active Noise Control ◽  
Absorption Enhancement ◽  
Reactive Material ◽  
Operation Conditions ◽  
Reducing Ability ◽  
Absorption Characteristics

For sound absorption of conventional porous materials, its noise-reducing ability in low frequencies is less than that in high frequency bands. A porous layer offers effective sound absorption when the thickness of layer is a quarter wavelength of the sound wave. Increasing the layer thickness is not an effective solution. Adjustment of rear air cavity volume for the porous medium has been used in practical applications to increase low frequency sound absorption. Noise reduction using only passive sound absorption characteristics is a challenge, especially when the operation conditions of noise source changes. In this study, we propose a smart porous material having noise reduction ability in the broad frequency band. We implement semi-active control by applying a magnetic reactive material to a porous medium. The smart foam proposed in this study reduced noise with adjustment of the magnitude and polarity of the magnetic field. Evaluation of its noise reduction performance is performed with the impedance tube method. Experiments are conducted for semi-active noise control of the proposed smart foam. The sound absorption characteristics are controlled efficiently with relatively low electric power consumption. A theoretical model to predict absorption characteristics is proposed using the transfer-matrix method, and its results show good agreement with measured behaviors.

Active control of compressor noise in the machinery room of refrigerators

2019 ◽  
Vol 67 (5) ◽  
pp. 350-362
Author(s):  
J. M. Ku ◽  
W. B. Jeong ◽  
C. Hong
Keyword(s):  
Control System ◽  
Active Control ◽  
Weighting Function ◽  
Reference Signal ◽  
Active Noise Control ◽  
Dominant Frequency ◽  
Time Signal ◽  
Frequency Noise ◽  
Sound Power ◽  
Fxlms Algorithm

The low-frequency noise generated by the vibration of the compressor in the machinery room of refrigerators is considered as annoying sound. Active noise control is used to reduce this noise without any change in the design of the compressor in the machinery room. In configuring the control system, various signals are measured and analyzed to select the reference signal that best represents the compressor noise. As the space inside the machinery room is small, the size of a speaker is limited, and the magnitude of the controller transfer function is designed to be small at low frequencies, the controller uses FIR filter structure converged by the FxLMS algorithm using the pre-measured time signal. To manage the convergence speed for each frequency, the frequency-weighting function is applied to FxLMS algorithm. A series of measurements are performed to design the controller and to evaluate the control performance. After the control, the sound power transmitted by the refrigerator is reduced by 9 dB at the first dominant frequency (408 Hz in this case) and 3 dB at the second dominant frequency (459 Hz here), and the overall sound power decreases by 2.6 dB. Through this study, an active control system for the noise generated by refrigerator compressors is established.

Endometrial Adenocarcinoma in SurePath™ Cervical Samples: Cytological Features Revisited

2016 ◽  
Vol 60 (1) ◽  
pp. 46-52 ◽  
Author(s):  
Nalini Gupta ◽  
John Crossley ◽  
Nick Dudding ◽  
John H.F. Smith
Keyword(s):  
Phase 1 ◽  
Endometrial Adenocarcinoma ◽  
Nuclear Chromatin ◽  
Phase 2 ◽  
Cervical Lesions ◽  
Two Phase ◽  
Endometrial Cells ◽  
Phase Study ◽  
Cytological Features ◽  
Liquid Based Cytology

Objective: The cytomorphological criteria of malignant endometrial lesions in cervical samples are less well described than those of cervical lesions. We wished to investigate if there were features in SurePath™ liquid-based cytology samples that would facilitate more accurate differentiation between benign and malignant endometrial cells. Study Design: This was a two-phase study, with a review of all SurePath™ samples reported as endometrial adenocarcinoma (n = 42) evaluating 12 cytological features in the first phase. In phase 2 (test set), all initial cases plus an additional 83 cases were reviewed using these 12 cytological features to predict the outcome. Results: Out of 12 cytological features evaluated in phase 1 (training set), nuclear chromatin pattern, apoptotic bodies and tingible body macrophages were found to be the most significant features determining malignant histological outcome. These 12 cytological features were re-evaluated in phase 2 (n = 125). Of 125 cases, 54 had a benign and 71 had a malignant or premalignant histological outcome, with a positive predictive value of 56.8%. Conclusion: Granular nuclear chromatin, tingible body macrophages and apoptosis in the background are the most significant factors in determining whether endometrial cells present in cervical samples represent malignancy or are benign. Using these features, relatively accurate predictions of endometrial pathology can be made.

166Ho-DOTMP plus melphalan followed by peripheral blood stem cell transplantation in patients with multiple myeloma: results of two phase 1/2 trials

Blood ◽  
2003 ◽  
Vol 102 (7) ◽  
pp. 2684-2691 ◽  
Author(s):  
Sergio Giralt ◽  
William Bensinger ◽  
Mark Goodman ◽  
Donald Podoloff ◽  
Janet Eary ◽  
...  
Keyword(s):  
Multiple Myeloma ◽  
Bone Marrow ◽  
Stem Cell ◽  
Hematopoietic Stem Cell Transplantation ◽  
Stem Cell Transplantation ◽  
Cell Transplantation ◽  
Phase 1 ◽  
High Dose ◽  
Two Phase ◽  
Hematopoietic Stem

Abstract Holmium-166 1, 4, 7, 10-tetraazcyclododecane-1, 4, 7, 10-tetramethylenephosphonate (166Ho-DOTMP) is a radiotherapeutic that localizes specifically to the skeleton and can deliver high-dose radiation to the bone and bone marrow. In patients with multiple myeloma undergoing autologous hematopoietic stem cell transplantation two phase 1/2 dose-escalation studies of high-dose 166Ho-DOTMP plus melphalan were conducted. Patients received a 30 mCi (1.110 Gbq) tracer dose of 166Ho-DOTMP to assess skeletal uptake and to calculate a patient-specific therapeutic dose to deliver a nominal radiation dose of 20, 30, or 40 Gy to the bone marrow. A total of 83 patients received a therapeutic dose of 166Ho-DOTMP followed by autologous hematopoietic stem cell transplantation 6 to 10 days later. Of the patients, 81 had rapid and sustained hematologic recovery, and 2 died from infection before day 60. No grades 3 to 4 nonhematologic toxicities were reported within the first 60 days. There were 27 patients who experienced grades 2 to 3 hemorrhagic cystitis, only 1 of whom had received continuous bladder irrigation. There were 7 patients who experienced complications considered to be caused by severe thrombotic microangiopathy (TMA). No cases of severe TMA were reported in patients receiving in 166Ho-DOMTP doses lower than 30 Gy. Approximately 30% of patients experienced grades 2 to 4 renal toxicity, usually at doses targeting more than 40 Gy to the bone marrow. Complete remission was achieved in 29 (35%) of evaluable patients. With a minimum follow-up of 23 months, the median survival had not been reached and the median event-free survival was 22 months. 166Ho-DOTMP is a promising therapy for patients with multiple myeloma and merits further evaluation. (Blood. 2003;102:2684-2691)

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