Evaluation of Aerodynamic Infrasound Radiating From Upwind and Downwind HAWTs

2012 ◽  
Author(s):  
Adrian Sescu ◽  
Abdollah A. Afjeh
Keyword(s):  
Flow Field ◽  
Wind Turbine ◽  
Sound Pressure ◽  
Low Frequency ◽  
Pressure Level ◽  
Frequency Noise ◽  
Far Field ◽  
Acoustic Analogy ◽  
Horizontal Axis Wind Turbines ◽  
Tower Shadow

A Computational Fluid Dynamics tool is used to determine the detailed flow field developing around two-blade horizontal axis wind turbines (HAWT) in downwind and upwind configurations. The resulting flow field around the wind turbine is used to evaluate the low-frequency noise radiating to the far-field, using an acoustic analogy method. The influence of the variation of wind velocity and rotational speed of the rotor to the sound pressure level is analyzed. This paper shows that the tower shadow effect of a downwind configuration wind turbine generates higher aerodynamic infrasound when compared to a corresponding upwind configuration. For validation, a comparison between numerical results and experimental data consisting of sound pressure levels measured from a two-blade downwind configuration wind turbine is presented.

Noise Prediction for Multi-Element Airfoil Based on FW-H Equation

2011 ◽  
Vol 52-54 ◽  
pp. 1388-1393
Author(s):  
Jun Tao ◽  
Gang Sun ◽  
Ying Hu ◽  
Miao Zhang
Keyword(s):  
Flow Field ◽  
Sound Pressure ◽  
Near Field ◽  
Pressure Level ◽  
Aerodynamic Noise ◽  
Noise Prediction ◽  
Far Field ◽  
Acoustic Analogy ◽  
Acoustic Information ◽  
Good Agreement

In this article, four observation points are selected in the flow field when predicting aerodynamic noise of a multi-element airfoil for both a coarser grid and a finer grid. Numerical simulation of N-S equations is employed to obtain near-field acoustic information, then far-field acoustic information is obtained through acoustic analogy theory combined with FW-H equation. Computation indicates: the codes calculate the flow field in good agreement with the experimental data; The finer the grid is, the more stable the calculated sound pressure level (SPL) is and the more regularly d(SPL)/d(St) varies.

Gyro Rock Crusher and Asphalt Plant Sound Power Levels

2012 ◽  
Author(s):  
Henry A. Scarton ◽  
Kyle R. Wilt
Keyword(s):  
Sound Pressure Level ◽  
Sound Pressure ◽  
Low Frequency ◽  
Pressure Level ◽  
Sound Power ◽  
Far Field ◽  
Atmospheric Attenuation ◽  
Frequency Sound ◽  
Sound Pressure Levels ◽  
Rock Crusher

Sound power levels including the distribution into octaves from a large 149 kW (200 horsepower) gyro rock crusher and separate asphalt plant are presented. These NIST-traceable data are needed for estimating sound pressure levels at large distances (such as occurs on adjoining property to a quarry) where atmospheric attenuation may be significant for the higher frequencies. Included are examples of the computed A-weighted sound pressure levels at a distance from the source, including atmospheric attenuation. Substantial low-frequency sound power levels are noted which are greatly reduced in the far-field A-weighted sound pressure level calculations.

scholarly journals Noise-silencing technology for upright venting pipe jet noise

2018 ◽  
Vol 10 (8) ◽  
pp. 168781401879481 ◽  
Author(s):  
Enbin Liu ◽  
Shanbi Peng ◽  
Tiaowei Yang
Keyword(s):  
Natural Gas ◽  
Sound Pressure Level ◽  
Sound Pressure ◽  
Low Frequency ◽  
Jet Noise ◽  
Pressure Level ◽  
Living Environment ◽  
Frequency Noise ◽  
Frequency Range ◽  
Expansion Chamber

When a natural gas transmission and distribution station performs a planned or emergency venting operation, the jet noise produced by the natural gas venting pipe can have an intensity as high as 110 dB, thereby severely affecting the production and living environment. Jet noise produced by venting pipes is a type of aerodynamic noise. This study investigates the mechanism that produces the jet noise and the radiative characteristics of jet noise using a computational fluid dynamics method that combines large eddy simulation with the Ffowcs Williams–Hawkings acoustic analogy theory. The analysis results show that the sound pressure level of jet noise is relatively high, with a maximum level of 115 dB in the low-frequency range (0–1000 Hz), and the sound pressure level is approximately the average level in the frequency range of 1000–4000 Hz. In addition, the maximum and average sound pressure levels of the noise at the same monitoring point both slightly decrease, and the frequency of the occurrence of a maximum sound pressure level decreases as the Mach number at the outlet of the venting pipe increases. An increase in the flow rate can result in a shift from low-frequency to high-frequency noise. Subsequently, this study includes a design of an expansion-chamber muffler that reduces the jet noise produced by venting pipes and an analysis of its effectiveness in reducing noise. The results show that the expansion-chamber muffler designed in this study can effectively reduce jet noise by 10–40 dB and, thus, achieve effective noise prevention and control.

scholarly journals Development of an on-site system for measuring the low-frequency noise and complainant’s responses

2018 ◽  
Vol 37 (2) ◽  
pp. 373-384
Author(s):  
Hiroshi Sato ◽  
Jongkwan Ryu ◽  
Kenji Kurakata
Keyword(s):  
Time Trends ◽  
Sound Pressure ◽  
Low Frequency ◽  
Dominant Frequency ◽  
Pressure Level ◽  
Frequency Noise ◽  
Low Frequency Noise ◽  
Measurement Results ◽  
Frequency Components ◽  
The Relationship

An on-site system for measuring low-frequency noise and complainant's responses to the low-frequency noise was developed to confirm whether the complainant suffer from the environmental noise with low-frequency components. The system suggests several methods to find the dominant frequency and major sound pressure level spectrum of the noise causing annoyance. This method can also yield a quantified relationship (correlation coefficient and percentage of response to the noise) between physical noise properties and the complainant’s responses. The advantage of this system is that it can easily find the relationship between the complainant’s response to the acoustic event of the houses and the physical characteristics of the low-frequency noise, such as the time trends and frequency characteristics. This paper describes the developed system and provides an example of the measurement results.

The Effect of Fluctuations on the Perception of Low Frequency Sound

2007 ◽  
Vol 26 (2) ◽  
pp. 81-89 ◽  
Author(s):  
A T Moorhouse ◽  
D C Waddington ◽  
M D Adams
Keyword(s):  
Laboratory Tests ◽  
Sound Pressure ◽  
Hearing Threshold ◽  
Low Frequency ◽  
Fast Response ◽  
Pressure Level ◽  
Rate Of Change ◽  
Frequency Noise ◽  
The Difference ◽  
Method Of Adjustment

Results of laboratory tests are presented in which 18 subjects, including some low frequency noise sufferers, were presented with low frequency sounds with varying degrees of fluctuation. Thresholds of acceptability were obtained for each sound and each subject, using the method of adjustment. These thresholds were then normalised to individual low frequency hearing threshold. It was found that sufferers tend to set thresholds of acceptability closer to their hearing threshold than other subject groups. Also, acceptability thresholds were set on average 5dB lower for fluctuating sounds. It is proposed that a sound should be considered fluctuating when the difference between L10 and L90 exceeds 5dB, and when the rate of change of the ‘Fast’ response sound pressure level exceeds 10dB/s

A Criterion for Predicting the Annoyance Due to Lower Level Low Frequency Noise

1983 ◽  
Vol 2 (4) ◽  
pp. 160-168 ◽  
Author(s):  
N. Broner ◽  
H.G. Leventhall
Keyword(s):  
Sound Pressure Level ◽  
Sound Pressure ◽  
Low Frequency ◽  
Threshold Effect ◽  
Pressure Level ◽  
The Other ◽  
Frequency Noise ◽  
Low Frequency Noise ◽  
Estimation Task ◽  
Noise Annoyance

In a study of the annoyance due to low frequency noise, 75 subjects (consisting of 21 complainants and 54 controls) carried out a magnitude estimation task and rated the annoyance due to lower-level low frequency noise (55dB–75dB). After allowing for a threshold effect, it was found that the E-weighted sound pressure level was, in general, the best predictor of lower-level low frequency noise annoyance. However, it was not a significantly better predictor than any of the other nine noise measures considered. The widely available dB(A) noise measure was therefore suggested as a useful predictor of group annoyance due to lower-level low frequency noise.

Process and Emergence on the Effects of Infrasonic and Low Frequency Noise on Inhabitants

1989 ◽  
Vol 8 (3) ◽  
pp. 87-99 ◽  
Author(s):  
Naoko Nagai ◽  
Masanobu Matsumoto ◽  
Yasukiyo Yamasumi ◽  
Tatsue Shiraishi ◽  
Koh Nishimura ◽  
...  
Keyword(s):  
Sound Pressure Level ◽  
Sound Pressure ◽  
Low Frequency ◽  
Peak Level ◽  
Pressure Level ◽  
Living Environment ◽  
Frequency Noise ◽  
Night Time ◽  
Questionnaire Method ◽  
Main Component

To clarify the process and emergence of the effects of infrasonic noise on man, the sound pressure level of infrasonic noise was measured in the area along a superhighway, and its effect on the inhabitants was investigated by the questionnaire method. The results are as follows: (1) The main component frequency of the infrasonic noise was 6.3 Hz. The sound pressure level (L50) of infrasonic noise (1–50 Hz) showed more than 85 dB in the daytime and more than 72 dB in the night time. It's peak level was above 100 dB under the overhead bridge of the superhighway. Indoors, the sound pressure level (L5) of infrasonic noise often went above 75 dB. (2) Answers about the living environment were given by 368 (85.6%) out of 430 families. Those about the condition of health were given by 909 cases (81.7%) out of 1113 cases who were all the inhabitants over 15 years of age. (3) 69.6% of families complained of the shaking of windows and the like. 65.8% of families complained of window rattling. More families complained of the shaking and rattling of windows in the area less than 80m distant from the superhighway, and more families also complained of the disturbance of sleep in that area. (4) The rates of the complaints as to ‘irritating’, have headaches', ‘head feels heavy’, ‘pain in arms or legs’, ‘feel languid’, ‘sleepless’, ‘dizziness’, ‘ringing in the ear’, and ‘difficulty in breathing’, were correlated with the distance from the superhighway. While the rate of complaints as to ‘have stiffness or pain on shoulders’ was highest, it had no relationship with the distance from the superhighway. From these results, it can be concluded that the inhabitants first complained of the shaking and rattling of windows by infrasonic noise, and then became chronically insomniac and excessively wearied by shaking and rattling of long continuance, and finally became highly sensitive to infrasonic noise. This increasing sensitivity might be closely connected with the emergence of the effect of infrasonic noise upon these inhabitants.

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