High-Frequency Noise Reduction in Mechanical Compartment of a Household Refrigerator via Dynamic Absorber Design

2020 ◽  
Author(s):  
Kyung-Chul Park ◽  
Won-Jin Kim ◽  
Jong-Seob Won
Keyword(s):  
Noise Reduction ◽  
High Frequency ◽  
Frequency Noise ◽  
High Frequency Noise ◽  
Dynamic Absorber

Car's Materials Acoustic Properties Test and Analysis

2013 ◽  
Vol 785-786 ◽  
pp. 1244-1247
Author(s):  
Yan Liu ◽  
Xiao Juan Zhang ◽  
Zong Cai Liu
Keyword(s):  
Noise Reduction ◽  
High Frequency ◽  
Sound Absorption ◽  
Transmission System ◽  
Acoustic Properties ◽  
Frequency Noise ◽  
Car Industry ◽  
High Frequency Noise ◽  
Urban Construction ◽  
The Impact

With the development of the car industry, the pace of the urban construction is accelerating as well. Cars have gradually entered the ordinary family. As the car noise has a big effect on the health of the passengers, as well as on the surroundings, one of the car industry key duties is the car noise reduction. By researching the materials applied to car, this article describe that PU material could reduce the impact of the engine noise on the cab efficiently; Polypropylene needle-spun felt could reduce the noise passed by chassis; PET material's sound absorption is poor in mid bass, however in high frequency it's sound absorption is good; sound absorbing sponge can reduce the low and high frequency noise; The combine sponge can reduce the noise from the tire and transmission system ; Cotton material could absorb the high frequency noise.

The Influence of Climatic Factors on the Distribution of Noise from Gas Distribution Stations

Vestnik MEI ◽  
2020 ◽  
Vol 5 (5) ◽  
pp. 79-83
Author(s):  
Vladimir B. Tupov ◽  
◽  
Vitaliy S. Skvortsov ◽  
Keyword(s):  
Noise Reduction ◽  
High Frequency ◽  
Climatic Factors ◽  
Frequency Noise ◽  
Octave Band ◽  
City Region ◽  
Gas Distribution ◽  
Central Frequency ◽  
High Frequency Noise ◽  
Maximum Range

The article discusses the influence of regional climatic factors on the propagation of noise from gas distribution stations (GDS), which are intense sources of noise for the surrounding area, and suggests a procedure for determining the required extent of noise reduction. GDSs produce high-frequency noise with the maximum values at the octave band central frequencies equal to 1000, 2000, 4000, and 8000 Hz. It is shown that climatic factors have quite a significant influence on the propagation of high-frequency noise from gas distribution stations precisely at the octave band central frequencies equal to 1000, 2000, 4000, 8000 Hz. The sound pressure levels may vary very significantly during a year depending on the region due to sound attenuation factors in the atmosphere. The climatic data for 210 cities of Russia were analyzed. The data on variation of climatic conditions during a year for these cities are taken from the Code SP 131.13330.2012. These changes for the octave band central frequency equal to 4000 Hz can make from the minimum range of 5.61 dB in the Sochi city region to the maximum range of 19.35 dB in the Chita city region; for the octave band central frequency equal to 8000 Hz they can make from the minimum range of 14.58 dB in the Elton city region to the maximum range of 48.63 dB in the Chita city region. The difference between the range smallest and largest values increases with the octave band central frequency. Thus, for the octave band central frequency equal to 1000 Hz this difference is 3 dB, whereas for the octave band central frequency equal to 8000 Hz this difference is 34 dB. The influence of climatic factors on the required extent of noise reduction from a GDS depends significantly on the region and can make tens of decibels for a combined heat and power plant with a 300-m wide sanitary protection zone. Therefore, for elaborating the necessary measures for reducing noise from a GDS, it is necessary to take into account the minimum atmospheric sound absorption coefficient for a particular region.

scholarly journals Reconfigurable Architecture for Multi-lead ECG Signal Compression with High-frequency Noise Reduction

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Mehdi Hasan Chowdhury ◽  
Ray C. C. Cheung
Keyword(s):  
Signal Processing ◽  
Noise Reduction ◽  
Real Time ◽  
High Frequency ◽  
Reconfigurable Architecture ◽  
Fast Fourier Transformation ◽  
Frequency Noise ◽  
Compression Rate ◽  
Processing Unit ◽  
High Frequency Noise

AbstractElectrocardiogram (ECG) is a record of the heart’s electrical activity over a specified period, and it is the most popular noninvasive diagnostic test to identify several cardiac diseases. It is an integral part of a typical eHealth system, where the ECG signals are often needed to be compressed for long term data recording and remote transmission. Reconfigurable architecture offers high-speed parallel computation unit, particularly the Field Programmable Gate Array (FPGA) along with adaptable software features. Hence, this type of design is suitable for multi-channel signal processing units like ECGs, which usually require precise real-time computation. This paper presents a reconfigurable signal processing unit which is implemented in ZedBoard- a development board for Xilinx Zynq −7000 SoC. The compression algorithm is based on Fast Fourier Transformation. The implemented system can work in real-time and achieve a maximum 90% compression rate without any significant signal distortion (i.e., less than 9% normalized percentage of root-mean-square deviation). This compression rate is 5% higher than the state-of-the-art hardware implementation. Additionally, this algorithm has an inherent capability of high-frequency noise reduction, which makes it unique in this field. The confirmatory analysis is done using six databases from the PhysioNet databank to compare and validate the effectiveness of the proposed system.

Optimum conditions for the high frequency noise reduction method in optical videodisc players

1986 ◽  
Vol 25 (9) ◽  
pp. 1398 ◽  
Author(s):  
Akira Arimoto ◽  
Masahiro Ojima ◽  
Naoki Chinone ◽  
Akio Oishi ◽  
Toshihoko Gotoh ◽  
...  
Keyword(s):  
Noise Reduction ◽  
High Frequency ◽  
Reduction Method ◽  
Frequency Noise ◽  
Optimum Conditions ◽  
High Frequency Noise

Case study: Simulation and control of high frequency noise for commercial vehicle cab considering leak

2019 ◽  
Vol 67 (4) ◽  
pp. 315-329
Author(s):  
Rongjiang Tang ◽  
Zhe Tong ◽  
Weiguang Zheng ◽  
Shenfang Li ◽  
Li Huang
Keyword(s):  
High Frequency ◽  
Commercial Vehicle ◽  
Frequency Noise ◽  
High Frequency Noise ◽  
Simulation And Control ◽  
And Control

Aerodynamic noise from an asymmetric airfoil with perforated extension plates at the trailing edge

2020 ◽  
pp. 1475472X2097838
Author(s):  
CK Sumesh ◽  
TJS Jothi
Keyword(s):  
High Frequency ◽  
Sound Pressure ◽  
Pore Diameter ◽  
Low Frequency ◽  
Aerodynamic Noise ◽  
Frequency Noise ◽  
Low Frequency Noise ◽  
Trailing Edge ◽  
High Frequency Noise ◽  
Displacement Thickness

This paper investigates the noise emissions from NACA 6412 asymmetric airfoil with different perforated extension plates at the trailing edge. The length of the extension plate is 10 mm, and the pore diameters ( D) considered for the study are in the range of 0.689 to 1.665 mm. The experiments are carried out in the flow velocity ( U∞) range of 20 to 45 m/s, and geometric angles of attack ( αg) values of −10° to +10°. Perforated extensions have an overwhelming response in reducing the low frequency noise (<1.5 kHz), and a reduction of up to 6 dB is observed with an increase in the pore diameter. Contrastingly, the higher frequency noise (>4 kHz) is observed to increase with an increase in the pore diameter. The dominant reduction in the low frequency noise for perforated model airfoils is within the Strouhal number (based on the displacement thickness) of 0.11. The overall sound pressure levels of perforated model airfoils are observed to reduce by a maximum of 2 dB compared to the base airfoil. Finally, by varying the geometric angle of attack from −10° to +10°, the lower frequency noise is seen to increase, while the high frequency noise is observed to decrease.

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