Retrieval of reflections from seismic background-noise measurements

ABSTRACT OBJECTIVE To perform a quantitative analysis of the background noise at Congonhas Airport surroundings based on large sampling and measurements with no interruption. METHODS Measuring sites were chosen from 62 and 72 DNL (day-night-level) noise contours, in urban sites compatible with residential use. Fifteen sites were monitored for at least 168 hours without interruption or seven consecutive days. Data compilation was based on cross-reference between noise measurements and air traffic control records, and results were validated by airport meteorological reports. Preliminary diagnoses were established using the standard NBR-13368. Background noise values were calculated based on the Sound Exposure Level (SEL). Statistic parameters were calculated in one-hour intervals. RESULTS Only four of the fifteen sites assessed presented aircraft operations as a clear cause for the noise annoyance. Even so, it is possible to detect background noise levels above regulation limits during periods of low airport activity or when it closes at night. CONCLUSIONS All the sites monitored showed background noise levels above regulation limits between 7:00 and 21:00. In the intervals between 6:00-6:59 and 21:00-22:59 the noise data, when analyzed with the current airport operational characteristics, still allow the development of additional mitigating measures.

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Interaction of seismic background noise with oscillating pore fluids causes spectral modifications of passive seismic measurements at low frequencies

10.1190/1.2792742 ◽

2007 ◽

Cited By ~ 2

Author(s):

Marcel Frehner ◽

Stefan M. Schmalholz ◽

Yuri Podladchikov

Keyword(s):

Background Noise ◽

Pore Fluids ◽

Low Frequencies ◽

Passive Seismic ◽

Seismic Background ◽

Seismic Measurements

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Background Noise Measurements at the Sea Horizon

Journal of the Optical Society of America ◽

10.1364/josa.49.001007 ◽

1959 ◽

Vol 49 (10) ◽

pp. 1007 ◽

Cited By ~ 5

Author(s):

Louis J. Free

Keyword(s):

Background Noise ◽

Noise Measurements

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Long-term ELF background noise measurements, the existence of window regions, and applications to earthquake precursor emission studies

Physics of The Earth and Planetary Interiors ◽

10.1016/0031-9201(93)90037-a ◽

1993 ◽

Vol 77 (1-2) ◽

pp. 109-125 ◽

Cited By ~ 5

Author(s):

Jack Y. Dea ◽

Peder M. Hansen ◽

Wolfgang-M. Boerner

Keyword(s):

Background Noise ◽

Earthquake Precursor ◽

Noise Measurements ◽

Emission Studies

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Impact of Aircraft Noise on Communities Near Belgrade Airport

PROMET - Traffic&Transportation ◽

10.7307/ptt.v33i3.3692 ◽

2021 ◽

Vol 33 (3) ◽

pp. 323-335

Author(s):

Emir Ganić ◽

Jurica Ivošević ◽

Bojana Mirković

Keyword(s):

Background Noise ◽

Aircraft Noise ◽

Current Noise ◽

Noise Levels ◽

Short Term ◽

Noise Abatement ◽

Compatibility Analysis ◽

Noise Measurements ◽

Continuous Noise ◽

The Impact

The aim of this research was to examine the impact of aircraft noise on communities near the Belgrade Airport by conducting short-term noise measurements. Apart from the noise abatement procedure published in the Aeronautical Information Publication for Belgrade Airport, there are still neither publicly available reports of the actual efforts made towards the aircraft noise reduction nor the description of the current noise situation. In order to estimate the current noise situation, eighteen aircraft overflight noise measurements were taken in two settlements in specific sound-sensitive community areas around the Belgrade Airport. The results showed that level differences between background noise and aircraft overflights were higher than 10 dB for each measurement and could be considered significant. Furthermore, preliminary compatibility analysis with acoustic zoning was performed. Average daily noise levels were estimated from these short-term measurements and were compared to legal noise limits for different acoustic zones. The results indicate that in some cases noise levels exceed the legal threshold, which should encourage land use planners to include the issue of Belgrade acoustic zoning on the agenda, but also prompt Belgrade Airport to implement continuous noise and flight tracks monitoring.

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Background Noise Definition for Acoustic Emission Leak Monitoring System at GTP Molve

Engineering Technology Conference on Energy, Parts A and B ◽

10.1115/etce2002/ee-29145 ◽

2002 ◽

Author(s):

Goran Hudec ◽

Boris Muvrin

Keyword(s):

Acoustic Emission ◽

Natural Gas ◽

Monitoring System ◽

Background Noise ◽

Acoustic Noise ◽

Treatment Plant ◽

Environment Impact ◽

Gas Treatment ◽

Noise Measurements ◽

The Impact

In Croatian Podravina relatively large quantities of natural gas was discovered. From various fields (Molve, Kalinovec, Stari Gradec) natural gas is pipelined to Gas Treatment Plant (GTP) Molve. Here, at GTP Molve III, technological procedures for purification of natural gas and its distribution are performed. With yearly natural gas production of 3,5 109 m3 GTP Molve III is major Croatian energy resource. Its safety and environment impact is matter of concern. Continuous acoustic emission leak monitoring system for Gas Treatment Plant (GTP) Molve as an improvement in technological and environment safety is considered. Application of a leak monitoring system under industrial conditions is a problem setting specific demands. In the paper attention is paid to some aspects of acoustic emission system implementation and the acoustic background noise definition problem. Acoustic noise measurements at a GTP Molve III were performed and some results considering background noise are presented. In the paper acoustic noise measurements performed at a GTP Molve III were presented. Across the GTP Molve III acoustical background have different spectral and amplitude characteristic. In the input area, measurements presented at a first group of measuring points included the impact of sand moved by gas fluid. Sand hits should be distinguished from acoustic emission caused by growing cracks. Motors noise and turbulence around valves are probably the main source of background noise on second group of measuring points. The conclusion is that background noise across the plant is highly different. Patterns found in one part of plant could not be applied on others measuring points. Background noise and its characterization are one of main problems solved before reliable operation of acoustic monitoring system could be applied. It is found that at GTP Molve III acoustic background is complicated, consisting of different sources at different part of a plant.

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High-frequency analysis of seismic background noise as a function of wind speed and shallow depth

Bulletin of the Seismological Society of America ◽

10.1785/bssa0860051507 ◽

1996 ◽

Vol 86 (5) ◽

pp. 1507-1515 ◽

Cited By ~ 8

Author(s):

Mitchell M. Withers ◽

Richard C. Aster ◽

Christopher J. Young ◽

Eric P. Chael

Keyword(s):

Wind Speed ◽

High Frequency ◽

Background Noise ◽

Signal To Noise Ratio ◽

Shallow Depth ◽

High Frequency Signal ◽

Wind Speeds ◽

Noise Characteristics ◽

Cultural Noise ◽

Seismic Background

Abstract We used a deep (1500 m) cased borehole near the town of Datil in west-central New Mexico to study high-frequency (>1 Hz) seismic noise characteristics. The remote site had very low levels of cultural noise, but strong winds (winter and spring) made the site an excellent candidate to study the effects of wind noise on seismograms. Along with a three-component set of surface sensors (Teledyne Geotech GS-13), a vertical borehole seismometer (GS-28) was deployed at a variety of depths (5, 43, and 85 m) to investigate signal and noise variations. Wind speed was measured with an anemometer. Event-triggered and time-triggered data streams were recorded on a RefTek 72-02 data acquisition system located at the site. Our data show little cultural noise and a strong correlation between wind speed and seismic background noise. The minimum wind speed at which the seismic background noise appears to be influenced varies with depth: 3 m/sec at the surface, 3.5 m/sec at 43 m in depth, and 4 m/sec at 85 m in depth. For wind speed below 3 to 4 m/sec, we observe omni-directional background noise that is coherent at frequencies below 15 Hz. This coherence is destroyed when wind speeds exceed 3 to 4 m/sec. We use a test event (Md ∼ 1.6) and superimposed noise to investigate signal-to-noise ratio (SNR) improvement with sensor depth. For the low Q valley fill of the Datil borehole (DBH) site, we have found that SNR can be improved by as much as 20 to 40 dB between 23 and 55 Hz and 10 to 20 dB between 10 and 20 Hz, by deploying at a 43-m depth rather than at the surface. At the surface, there is little signal above noise in the 23- to 55-Hz frequency band for wind speeds greater than 8 m/sec. Thus, high-frequency signal information that is lost at the surface can be recorded by deploying at the relatively shallow depth of 40 m. Because we observe only minor further reductions in seismic background noise (SBN) at deeper depths, 40 m is likely to be a reasonable deployment depth for other high-frequency-monitoring sites in similar environmental and geologic conditions.

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