1 edition of **Time domain modal beamforming for a near vertical acoustic array** found in the catalog.

Time domain modal beamforming for a near vertical acoustic array

Steven Edward Crocker

- 210 Want to read
- 11 Currently reading

Published
**1991**
by Naval Postgraduate School, Available from the National Technical Information Service in Monterey, Calif, Springfield, Va
.

Written in English

**Edition Notes**

Statement | by Steven E. Crocker |

Contributions | Miller, James H. |

The Physical Object | |
---|---|

Pagination | 89 p. ; |

Number of Pages | 89 |

ID Numbers | |

Open Library | OL25497913M |

This paper proposes a mode domain beamforming method for a 3 × 3 uniform rectangular array of two-dimensional (2D) acoustic vector sensors with inter-sensor spacing much smaller than the. In a previous article [T. C. Yang, J. Acoust. Soc. Am. 82, – ()], range and depth were successfully estimated by modal beamforming. In this article, the modal beamforming array gain is derived in closed form for a vertical array of N hydrophones. For the case of white noise and a long well‐populated vertical array, the array gain nearly equals 10 log N.

Beamforming or spatial filtering is a signal processing technique used in sensor arrays for directional signal transmission or reception. This is achieved by combining elements in an antenna array in such a way that signals at particular angles experience constructive interference while others experience destructive interference. Beamforming can be used at both the transmitting and receiving. In a previous paper [T. C. Yang, J. Acoust. Soc. Am. 82, – ()], range and depth were successfully estimated by modal beamforming. In this paper, the modal beamforming array gain in closed form for a vertical array of N hydrophones is derived. For the case of white noise and a long well‐populated vertical array, the array gain nearly equals 10 log N.

• Beamforming is spatial filtering, a means of transmitting or receiving sound preferentially in some directions over others. • Beamforming is exactly analogous to frequency domain analysis of time signals. • In time/frequency filtering, the frequency content of a time . VOCAL Technologies, Ltd. Lee Entrance, Suite Buffalo, NY Phone: +1 Fax: +1 Email: [email protected]

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A time domain modal beamformer for a near vertical acoustic array has been developed. It has realized a nominal array gain of 6 dB for the Heard Island Experiment vertical array deployed off.

A time domain modal beamformer for a near vertical acoustic array has been developed. It has realized a nominal array gain of 6 dB for the Heard Island Experiment vertical array deployed off California. The primary obstacle to the technique remains inadequate array geometry description.

A time domain modal beamformer for a near vertical acoustic array has been developed. It has realized a nominal array gain of 6 dB for the Heard Island Experiment vertical array deployed off : Steven Edward Crocker.

Abstract: Modal beamformer for circular arrays, which is based on a circular harmonics decomposition of the sound field, is flexible for use because it is decoupled from the sensor positions.

A time-domain implementation of broadband modal beamformer for circular arrays is presented in this paper. This beamforming structure consists of a real-valued circular harmonics transform and Cited by: 1. The chapter describes the time‐domain signal model and explains how broadband beamforming works.

Then, it defines many performance measures that are essential for the derivation and analysis of broadband beamformers. Some measures are only relevant for fixed beamforming while others are more relevant for adaptive beamforming.

Time and Frequency Domain SONAR Beamforming in the Near-Field by Niko Moritz Figure Acoustic pressure allocation of a linear antenna focused to ∞ (located at x=0 m, y= Simulation of real-time beamforming by the phase shift method for a CW signal. Abstract: Conventional methods for modal beamforming of underwater acoustic signals using a vertical-line hydrophone array (VLA) can suffer significant degradation in resolution when the array is geometrically deficient, i.e., consists of sparsely spaced elements and spans the water column partially or is poorly navigated.

Designed for estimating the coefficients of the normal modes, these. The aim of this paper is then to show that the time-domain beamforming technique allows assessing the intermittent nature of aeroacoustic sources, and makes possible a space-time tracking of short duration acoustic events occurring in the ﬂow.

The method is. The Acoustic Camera can be used for Beamforming, Intensity and Holography. On our website we explain the most important terms in the FAQ for understanding how Beamforming works. The functionality of the Delay-And-Sum-Beamformer can be described by decomposing the signal processing into four main block diagram in Figure 1 illustrates the case of two point sources situated in.

Acoular is a Python module for acoustic beamforming that is distributed under the new BSD license. It is aimed at applications in acoustic testing. Multichannel data recorded by a microphone array can be processed and analyzed in order to generate mappings of sound source distributions.

An approach to real-valued time-domain implementation of modal beamformer for spherical microphone arrays is proposed. The advantage of the time-domain implementation is that we can update the beamformer when each new snapshot arrives. Our technique is based on a modified filter-and-sum spherical harmonics domain (SHD) beamform- ing structure.

Time-domain Beamforming using 3D-microphone arrays is an extremely fast, easy and simple way to find sources inside cavities. Source-characteristic, room-acoustic and array-geometry will set limits to the resolution and display in acoustic pictures. In our previous article we explained Delay-And-Sum-Beamforming in the Time Domain (TDBF).

The Delay-And-Sum-Beamformer in the Frequency Domain is based on a similar principle as in the time domain. The block diagram in Figure 1 illustrates the case of two point sources situated in a measurement plane in front of the microphone array.

compact and high-performance acoustic arrays [3]. A modal beamformer for circular pressure arrays was derived from an optimum processing perspective and was experimentally validated using a hydrophone array [4].

A circular modal beamformer that relies on 2-D vector sensors was proposed by Zou [6]. In this paper, a modal beamformer similar to. implement time domain and frequency domain beamforming systems.

It takes a very simplistic approach to the problem and should not be considered as definitive in any sense. TIME DOMAIN SONAR BEAMFORMING. Consider an array of hydrophones receiving signals from an acoustic source in the far-field (Figure 1a). Calculation in the time domain The simplest approach is the straightforward calculation of a delay-and-sum-beamformer in the time domain.

The reconstructed time function at every location x is calculated as: (). 1 ˆ (,) 1 ∑ = = −Δ M i w f t i i i M x f t (1) In Eq. (1), denotes time, t M is the number of microphones in the sensor.

Optimal Modal Beamforming for Spherical Microphone Arrays Abstract: An approach to optimal array pattern synthesis based on spherical harmonics is presented. The array processing problem in the spherical harmonics domain is expressed with a matrix formulation.

The beamformer weight vector design problem is written as a multiply constrained. of phased array results using a Multi-Modal-Beamforming approach. The method allows the reduction of the main lobe width as well as the suppression of the side lobes of acoustic sources in the map and can thus be applied for the improvement of the usually very bad image contrast in the lower frequency range and also for a better separation.

ization and beamforming problems are formulated in Sec. In Sec-tion 3, MINT, an optimal ﬁlter-and-sum beamformer and a hybrid reference algorithm are formulated in the time domain. The algo-rithms are evaluated in Section 4 and conclusions are drawn in Sec-tion 5.

PROBLEM FORMULATION Consider an array of Mmicrophones placed in a. An approach to optimal design of circular harmonics based modal beamformers for circular arrays is presented. Theoretical analysis shows the equivalence between the element-space and circular-harmonics-domain beamformers.

By deriving the expression for the signal and noise covariance matrices, array manifold, and the array response in terms of the circular-harmonics-domain beamforming. Modal array signal processing, as treated in this book, comprises waveform estimation tasks, i.e.

beamforming, as well as parameter estimation tasks, i.e. source localization and the estimation of.For a linear array with uniform sensor spacing d, the time delay between the adjacent sensors is given by (2) where c is the velocity of medium.

The time delay between 1st and th sensor will be In a narrow band frequency domain beamformer, (3) If w 1 w M are the weights to be multiplied to each of the. The sound speed profile of water column in Fig. 1, approximately constant at m/s, was measured near the hydrophone array.

Below the 40 m water column was a fluid sea bottom. One element vertical array was deployed spanning the whole water column. Table I shows the recorded depths for 15 working sensors during the experiment.