题目：Estimation of low frequency sound attenuation in marine sediments 时间：2016年4月14日上午 9:30-11:30 地点：玉泉校区信电楼117-119会议室 报告人：N. Ross Chapman

Abstract: This paper presents a method for estimating low frequency sound attenuation from information contained in normal modes of a broadband signal.  Propagating modes are resolved using the time-warping technique applied to signals from light bulb sound sources deployed at relatively short ranges of 5 and 7 km in the Shallow Water ’06 experiment.  A sequential inversion approach is designed that uses specific features of the acoustic data that are highly sensitive to specific geoacoustic model parameters.  The first feature is the modal group velocity which is inverted for sediment sound speed and sediment layer thickness.  The second feature is the modal amplitude function which is inverted for water depth and receiver depths.  The third feature is related to the modal amplitude spectra, and is inverted for source depth and sound attenuation.  In each subsequent stage, estimates from the previous stage(s) are used as known values.  The sequential inversion is stable and generates geoacoustic model parameter estimates that agree very well with results from other experiments carried out in the same region. Notably, the inversion obtains an estimated value of 0.08 dB/l in the band 120-180 Hz for the de-watered marine sediment characteristic of the continental shelf at the site.

Biography: Ross Chapman recently retired from the University of Victoria following a career of over 35 years in underwater acoustics, signal processing and acoustical oceanography.  He obtained a PhD in physics at the University of British Columbia in 1975, and started work in Defence Research in Canada as Leader of the Ocean Acoustics Group (1976-1995), before moving on to the University of Victoria as a Research Chair in Ocean Acoustics, and Director of the Centre for Earth and Ocean Sciences at the University of Victoria (2000-2006).  He has published over 130 papers and book chapters, and continues to maintain his research interests in ocean acoustic propagation and modelling, advanced signal processing, ocean ambient noise measurement and modeling, and inversion of ocean seabed properties from acoustic field data. He is an elected Fellow of the Institute of Electrical and Electronic Engineers and the Acoustical Society of America, and is Editor in Chief of the IEEE Journal of Oceanic Engineering.