Latest research results for 2008

• Design and characterisation of wideband electrostatic transducers for replication of bat call in air [PDF]
• Detection and analysis of echolocation calls from the megachiropteran rousettus aegyptiacus using a bat-mounted wirelesss sensor [PDF]
• Monitoring and control of underwater wideband transducers [PDF]

Research results for 2007

• Wideband air-coupled transducer design [PDF]
• Radio-telemetry of bat sonar signals [PDF]
• Bio inspired ranging finding algorithm (BIRA) [PDF]
• Monitoring and control of wideband sonar transducers [PDF]

Within the BIAS consortium, The University of Strathclyde has research interests focussed around the following main areas:

• Air-coupled transducers
• Water-coupled transducers
• Transducer development
• Drive modification and instrumented transducers
• Wireless instrumentation
• Ranging algorithms

Fundamentally, the research at Strathclyde University is driven by the desire to enhance imaging and ranging performance of transducer hardware in both air and water coupled environments. To this end a number of novel transducer technologies and signal processing approaches have been developed by CUE (Centre for Ultrasonic Engineering) and CESIP (Centre for excellence in Signal and Image Processing). For air coupled transduction, research has concentrated on electrostatic approaches using novel backplate machining to enhance the spectral response of these devices. Theoretical device modelling has been complemented by extensive prototype fabrication, and experimental verification of performance characteristics (radiated sound field measurements, impulse response). Applications for these broadband air-coupled devices lie in improved location methodologies (for example in autonomous robotics), where the improved ranging algorithms developed by CESIP can be exploited.

SEM images of micromachined pits and the effect on transducer response.

A significant focus for the air coupled work has involved the integration of wideband transducers into a fully wireless instrumentation system for monitoring real bat echolocation calls. In close collaboration with The University of Leeds, CUE has developed a miniature wireless “bat-pack” capable of monitoring both outgoing and target echo signals from bats in flight. The aim of this research is to better understand the characteristics of real bat echolocation calls and their interaction with real targets; the ultimate goal being to use this understanding to devise new approaches to air coupled ultrasonics.

R.aegyptiacus pictured with dorsally-mounted sensor

In the underwater SONAR environment, CUE has developed new transducer technologies based around active inversion layers combined with optimised multilayer matching systems designed to optimally couple acoustic energy into the target medium. These approaches are appropriate for use in both single element and large multi-element array devices. In addition to this hardware based approach (again with significant modelling, prototyping and experimental performance verification), CUE is also pursuing research into active monitoring and control of SONAR transducers. By incorporating a monitoring capability into the transducer construction, it will be possible to directly monitor the real acoustic output of a transducer and furthermore to compensate the drive signal such as to optimise the output. Current research focuses around optical fibre based sensing systems (phase, polarisation and wavelength based).

A polarimetric sensor attached across the surface of a transducer.