Linearly filtered estimation of the time-domain Green’s function from measurements of ambient noise

Albahrani, Sayed Ali; Frater, Michael R.; Huntington, Elanor H.

doi:10.1121/1.2981049

Cited by 3 publications

(10 citation statements)

References 15 publications

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“…The resolution of the CCF can be defined as the full width of the main lobe of the correlation peak [6]. A decrease in the peak width means an improvement in the [6,17] lar frequency is unde phones is used to make use of beamform fo ai frequency components of the broadband data.…”

Section: Relationship Between Snr Resolution and Bandwidthmentioning

confidence: 99%

“…The pulses shown in Figure 9 resemble the peak shown in Figure 8 with the main difference is that strong negative pulse is shown in the Jervis Bay noise field compared to Figure 9. The negative pulse is generated by the effect of applying high pass filter on the recorded noise field [6].…”

Section: Cross-correlation Between Ocean Ambientmentioning

confidence: 99%

“…A decrease in the peak width means an improvement in the [6,17] lar frequency is unde phones is used to make use of beamform fo ai frequency components of the broadband data. …”

Section: Relationship Between Snr Resolution and Bandwidthmentioning

confidence: 99%

“…The number of elements of the array can be increased to increase the SNR of the correlation function [2,5,10], but the array becomes physically larger. The increase in the number of elements does not increase the resolution of the correlation because the resolution is dependent on the bandwidth of the noise field [6].…”

Section: Introductionmentioning

confidence: 99%

“…The estimate in the passive fathometer is based on the extraction of the Green's Function (GF) from the ambient Noise Crosscorrelation Function (NCF) [2]. The GF between two points can be extracted from the derivative of the crosscorrelation between the Ocean Ambient Noise (OAN) received at those two points [6][7][8]. The better the estimate of the GF, the better the estimate in the passive fathometer.…”

Section: Introductionmentioning

confidence: 99%

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Effect of Biological Activity on Broadband Passive Fathometry

Alam¹,

Huntington²,

Frater³

2013

OJA

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A passive fathometer can be formed by two vertically separated hydrophones. The depth can be estimated from the Green's function between the hydrophones, which is calculated from the cross-correlation between ocean ambient noise fields received at those two hydrophones. The performance of the fathometer depends on the signal to noise ratio (SNR) and the resolution of the noise cross-correlation function. In a given environment, improved SNR and resolution of the cross-correlation function can be achieved through longer observations, more observation points, or increasing bandwidth. Long time averaging has been demonstrated, but requires that the channel be stationary over the averaging time. Hydrophone arrays are commonly used, but result in increased cost and complexity. Recent work shows that the SNR and resolution of the correlation function can also be improved by the use of the large bandwidth noise fields. This paper shows that the non-surface biological noise generated by marine animals, such as shrimp, is one of the major issues in the performance of such a broadband passive fathometer operating in shallow water. This noise tends to occur at higher frequencies. Frequencies at which significant non-surface biological noise is present cannot be used to improve fathometer performance. Consequently, the upper limit of frequencies that can be used in a passive fathometer is limited by the lower limit of the bandwidth occupied by the biological noise.

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Section: Relationship Between Snr Resolution and Bandwidthmentioning

confidence: 99%

Section: Cross-correlation Between Ocean Ambientmentioning

confidence: 99%

“…A decrease in the peak width means an improvement in the [6,17] lar frequency is unde phones is used to make use of beamform fo ai frequency components of the broadband data. …”

Section: Relationship Between Snr Resolution and Bandwidthmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Effect of Biological Activity on Broadband Passive Fathometry

Alam¹,

Huntington²,

Frater³

2013

OJA

Self Cite

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Improving resolution and SNR of correlation function with the increase in bandwidth of recorded noise fields during estimation of bottom profile of ocean

Alam

Frater

Huntington

2010

Oceans'10 Ieee Sydney

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Cross-correlation of coherent wave fronts of acoustic ambient noise fields gives an estimation of the bottom profile of ocean. Hydrophones are used to record the noise fields. Averaging time needed for estimating depth of sea bed depends on the number of coherent wave fronts extracted from the noise fields. In the current approach of depth estimation if only two hydrophones are used to record the acoustic noise fields ,then it takes large amount of averaging time to extract sufficient amount of coherent wave fronts for estimating depth of sea bed. Use of a vertical array of hydrophones for noise field recording and later by combining the cross-correlation of all hydrophone pairs of the vertical array a stronger signature can be obtained and this greatly reduces averaging time. Reduction of averaging time can be expressed as increase in signal to noise ratio (SNR) and resolution of correlation function. Main goal of this paper is to increase SNR and resolution of correlation function using only two hydrophones and proper use of bandwidth of recorded noise fields. It isshown that recording large bandwidth signals in two hydrophones greatly increases SNR and resolution of correlation hence reduces the averaging time needed for estimating depth of sea bed. Results of this paper were verified using mathematical expression and simulation.

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Trade-Off between Bandwidth and Number of Array Elements in the Performance Enhancement of Passive Fathometer

Alam

Huntington²,

Frater³

2013

OJA

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Improved signal to noise ratio (SNR) and resolution of the ambient noise cross-correlation function (NCF) between two points help in the estimation of bottom profile of the ocean. One of the main requirements of the improvement of the SNR and resolution is collection of a large amount of data. These large amounts of data can be achieved by recording a large bandwidth ambient noise or using an array of hydrophones. This paper evaluates the performance of the array processing and compares it to the large bandwidth technique in terms of SNR and resolution of NCF. It is shown that the large bandwidth technique gives better SNR and resolution compared to the array processing technique under certain conditions. The outcome of this article finds application in the enhanced estimation of the passive fathometer.

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Linearly filtered estimation of the time-domain Green’s function from measurements of ambient noise

Cited by 3 publications

References 15 publications

Effect of Biological Activity on Broadband Passive Fathometry

Effect of Biological Activity on Broadband Passive Fathometry

Improving resolution and SNR of correlation function with the increase in bandwidth of recorded noise fields during estimation of bottom profile of ocean

Trade-Off between Bandwidth and Number of Array Elements in the Performance Enhancement of Passive Fathometer

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