scholarly journals Acoustic measures of low-frequency noise in extended high-frequency audiometry

2007 ◽  
Vol 121 (3) ◽  
pp. EL120-EL124 ◽  
Author(s):  
Nicolas Schmuziger ◽  
Matthias Brechbuehl ◽  
Rudolf Probst
Keyword(s):  
High Frequency ◽  
Low Frequency ◽  
Frequency Noise ◽  
Low Frequency Noise ◽  
Acoustic Measures ◽  
High Frequency Audiometry

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.

Comparison of low frequency noise and high frequency performances of double and simple polysilicon Bi-CMOS BJT

2000 ◽  
Vol 40 (11) ◽  
pp. 1869-1874 ◽  
Author(s):  
C Delseny ◽  
A Pénarier ◽  
F Pascal ◽  
S.G Jarrix ◽  
P Llinares
Keyword(s):  
High Frequency ◽  
Low Frequency ◽  
Frequency Noise ◽  
Low Frequency Noise

scholarly journals Effect of personality traits on sensitivity, annoyance and loudness perception of low- and high-frequency noise

2020 ◽  
pp. 146134842094581
Author(s):  
Milad Abbasi ◽  
Mohammad Osman Tokhi ◽  
Mohsen Falahati ◽  
Saeid Yazdanirad ◽  
Maryam Ghaljahi ◽  
...  
Keyword(s):  
Personality Traits ◽  
High Frequency ◽  
Low Frequency ◽  
Analysis Of Covariance ◽  
Frequency Noise ◽  
Low Frequency Noise ◽  
High Frequency Noise ◽  
Noise Annoyance ◽  
Significant Difference ◽  
Frequency Components

This paper presents investigations into a comparative assessment of the effects of low- and high-frequency noise in relation to personality traits. The high- and low-frequency noises used are produced in the research laboratory using CoolEdit software. In all, 80 candidates were exposed to equivalent continuous sound pressure level of 65 dBA of low- and high-frequency noise in an acoustic room with a 2-week interval. After 1 hour of exposure to noise, participants were asked to complete noise annoyance scale, Weinstein noise sensitivity questionnaire and loudness perception. The results obtained indicate that there is a significant difference between annoyance and perception of low-frequency noise in comparison to annoyance and perception of high-frequency noise, but no significant difference is noted between sensitivity to low- and high-frequency noise. The multivariate analysis of covariance test is applied, which reveals that personality traits have a significant effect on sensitivity to low- and high-frequency noise, annoyance due to low- and high-frequency noise, loudness perception of low-frequency noise, but no interaction effects are found. It is further shown that personality traits are more effective on sensitivity, annoyance and loudness perception to high-frequency noise than those of low-frequency noise, and such effects are not only influenced by severity of noise but also by personality traits and frequency components.

scholarly journals Features of time variations of microseismic noise at seismic stations in Tajikistan

2021 ◽  
Vol 3 (4) ◽  
pp. 18-37
Author(s):  
Vladimir Zhuravlev ◽  
Albert Lukk
Keyword(s):  
High Frequency ◽  
Noise Level ◽  
Low Frequency ◽  
Frequency Noise ◽  
Noise Amplitude ◽  
Low Frequency Noise ◽  
Frequency Range ◽  
Seismic Stations ◽  
High Frequency Noise ◽  
40 Hz

The spectral structure of microseismic noise in the frequency range of 0.01-40 Hz at different times of the day and year, recorded by broadband equipment at eight IRIS group seismic stations in Tajikistan in 2005-2020, was analyzed. Two disjoint frequency ranges are distinguished, which we conditionally call "high-frequency" (2-40 Hz) and "low-frequency" (0.01-0.75 Hz) noise, separated by a natural drop in the noise amplitude to 20-30 Db. It is assumed that the high-frequency range of noise has a local nature, due to exogenous sources of natural origin in the form of wind gusts, concussions from powerful watercourses and fluctuations in the level of large reservoirs, as well as man-made in-terference due to road and quarry explosions, the work of large industrial enterprises and concussions from road traffic. Low-frequency noise is most likely caused by global storm microseisms. High-frequency noise has a well-defined daily frequency, which is completely absent in low-frequency noise. At the same time, in both frequency ranges, the existence of a clearly pronounced seasonal peri-odicity has been established, the amplitude of which reaches 6-7 Db for high-frequency noise and about half as much for low-frequency noise. However, at the same time, the seasonal frequency of high frequency and low-frequency noise turns out to be antiphase, which indicates in favor of the different genesis of these two components of microseismic noise. The amplitude of the diurnal periodicity in variations of the high-frequency noise level is maximal during the daytime, remaining approximately constant for 8-10 hours. At the same time, the decline in the noise amplitude in the evening lasts longer than the steeper morning growth. The time intervals of a sharp increase and decrease in the intensity of the discussed daily extreme are quite well correlated, respectively, with morning and evening twilight at different times of the year. This is reflected in the wider flat part of the maximum noise level in summer compared to winter and the differences in its level up to 6 Db in favor of summer time. This observation can be considered as a manifestation of the deep influence of the Sun on the oscillatory processes that generate high-frequency microseismic noise.

Giant enhancement of low-frequency noise as precursor for the onset of a high-frequency instability

2009 ◽  
Author(s):  
P. Shiktorov ◽  
E. Starikov ◽  
V. Gružinskis ◽  
L. Varani ◽  
L. Reggiani ◽  
...  
Keyword(s):  
High Frequency ◽  
Low Frequency ◽  
Frequency Instability ◽  
Frequency Noise ◽  
Low Frequency Noise

Estimating the Quality of Thermionic Cathodes for Microwave Vacuum Tubes Using the Low-Frequency Noise Parameters

Vestnik MEI ◽  
2018 ◽  
Vol 5 (5) ◽  
pp. 120-127
Author(s):  
Mikhail D. Vorobyev ◽  
◽  
Dmitriy N. Yudaev ◽  
Andrey Yu. Zorin ◽  
◽  
...  
Keyword(s):  
Low Frequency ◽  
Frequency Noise ◽  
Low Frequency Noise ◽  
Noise Parameters ◽  
Thermionic Cathodes ◽  
Vacuum Tubes
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