Ambient Noise Imaging-first deployments of ROMANIS and preliminary data analysis

Abstract

-The Acoustic Research Laboratory (ARL) at the Tropical Marine Science Institute under the National University of Singapore has developed a second generation Ambient Noise Imaging (ANI) system: the Remotely Operated Mobile Ambient Noise Imaging System (ROMANIS). ROMANIS has been primarily developed to study the potential of ANI applications where snapping shrimp are the major natural insonifiers of the environment, as in warm shallow waters like those surrounding Singapore. ROMANIS is a fully digital broadband data acquisition and recording system with over 500 sensors that fully populate a circular aperture of 1.4m. The first at sea deployment was conducted during February 2003 to check the functionality of the system in a real seawater environment (that differs considerably in terms of electronic and acoustic noise from previous tests in tank) and to study the high frequency ambient noise characteristics at the deployment location. It was also required to validate the beamforming algorithms developed for imaging. A GUI-based application helps the user to control the acquisition process and acquire the data synchronously. Approximately 750 Mbytes of data was recorded. A custom software package has been developed which enables reading, processing and the displaying of images from the recorded data. In this paper we present the deployment details and preliminary analysis of the data. The analysis confirms that the energy distribution from snapping shrimp clicks follow a lognormal distribution as previously reported. The validity of the beamforming software has been verified with a 40 kHz pinging source placed some 50 m away from ROMANIS and forming an image of it from the data recorded. A second deployment of the system has been made during MayJune 2003 with targets placed at ranges exceeding any attempted to date and to produce their acoustic images. The data from these recordings are under analysis and some part of it is presented in this paper.

Preliminary analysis of background noise distribution in the ocean experiment 2010 of Ambient Noise Imaging

“…For example, Epifanio et al built the acoustic daylight ocean noise imaging system, consisting of a 3-m diameter spherical reflector with an array of 126 hydrophones attached to the focal surface [2]. The remotely operated mobile ambient noise imaging system, with a 2-D sparse array of 504 hydrophones fully populating a 1.44-m circular aperture, was built by Venugopalan et al [3]. Both systems successfully detected silent target objects under the dominant noise of snapping shrimp.…”

Extraction of Target Scatterings from Received Transients on Target Detection Trial of Ambient Noise Imaging with Acoustic Lens

“…It was successfully used to image some silent targets using natural ocean ambient noise, which was mostly generated by snapping shrimp in San Diego Bay, southern California. 2) In the early 2000s, the remotely operated mobile ambient noise imaging system (ROMANIS) was developed by Venugopalan et al 3) ROMANIS was constructed with a two-dimensional sparse array of 504 hydrophones on a 1.44-m-diameter disk aperture, and realizes a resolution of 1 at 60 kHz. Target objects were also successfully detected using snapping shrimp dominant noise in warm shallow water around Singapore.…”

Numerical Simulation of Target Range Estimation Using Ambient Noise Imaging with Acoustic Lens

“…2) Recently, Venugopalan et al have built the remotely operated mobile ambient noise imaging system (ROMANIS), consisting of a two-dimensional (2D) sparse array of 504 hydrophones fully populating a 1.44 m circular aperture. 3) Both systems successfully detected target objects using snapping shrimp dominant noise in coastal water.…”