Ambient Noise Imaging

The Concept

Ambient Noise Imaging (ANI) is one of the major research areas in ARL. The principle underlying this phenomenon makes use of the ensonification provided by the ambient noise field to create pictorial images of underwater objects. Ambient noise imaging is well suited for the warm shallow waters of SE Asia, where snapping shrimp serve as an excellent source of illumination.

The ARL has developed a class of new algorithms including the one based on the Acoustic Daylight (AD) idea to form images out of the ambient noise data. ARL has also built a system called Remotely Operated Mobile Ambient Noise Imaging System (ROMANIS), an ambient noise imaging underwater acoustic camera. The system underwent its first underwater functional test recently.

Remotely Operated Mobile Ambient Noise System (ROMANIS)

ROMANIS is a digital broad band ANI camera which will be able to form high resolution images over 25-85 kHz band. The ARL has already built the camera and it has undergone so far two successful functional trials in Singapore waters. Some of the highlights of the system are:

  • A fully populated but sparsely sampled 1.5m diameter circular array comprising of 504 hydrophone elements

  • Broadband system covering 25-85 kHz

  • Highly hierarchical and modular design

  • 54 Pentium processors (PC104Plus) connected over Fibre Channel Arbitrated Loops (FC-AL); this is the first time Fibre Channel technology is being employed in an underwater system

  • Synchronous sampling and the data streamed at the rate of 1.6 Gbps

  • Fibre Channel storage system and user controlled data acquisition

  • No potted or oil-filled sensors; a neoprene acoustic window

  • ROMANIS is gas filled with 0.5 atmosphere of Helium for better thermal conduction

The 'Acoustic eye' of ROMANIS

Click here to find out more about ROMANIS.