Modification of Attenuation Rate in Range Normalization of Echo Levels for Obtaining Frequency-dependent Intensity Data from 0.6MHz and 1.0MHz Devices
DOI:
https://doi.org/10.5614/j.eng.technol.sci.2013.45.2.3Abstract
This investigation aims to propose an attenuation rate for range normalization of echo amplitudes recorded by an acoustic backscattering instrument working at a frequency of 1.0 MHz. The intention of the use of such an attenuation rate is to obtain equal echo levels when using a device from the same family of products with a different working frequency, i.e. a 0.6 MHz instrument, at an identical site. This work is based on a field experiment with a 1.0 MHz Acoustic Wave and Current (AWAC) profiler and a 0.6 MHz Aquadopp profiler. Both profilers were deployed upward, side-by-side in the Semak Daun reef lagoon, Seribu Islands, Java Sea, Indonesia. It was found that the proposed attenuation rate for the 1.0 MHz instrument was one-order magnitude higher with respect to the one used for the 0.6 MHz instrument, and logarithmically depth dependent. The proposed attenuation rate for the 1.0 MHz AWAC is "?7.925log(R) + 8.551, with R is the slant range from the transducers to the measured layer. Accordingly, the overall agreement between the 1.0 MHz AWAC echo amplitude and the one recorded by the 0.6 MHz Aquadopp was improved by 18dB, which is quite significant considering that the average echo amplitude discrepancy recorded by each transducer was 2.4dB.Downloads
References
Thorne, P.D., Hardcastle, P.J. & Soulsby, R.L., Analysis of Acoustic Measurements of Suspended Sediments, Journal of Geophysical Research, 98(C1), pp. 899-910, 1993.
Deines, K.L., Backscatter Estimation Using Broadband Acoustic Doppler Current Profilers, In: Anderson, S.P., Terry, E.A., White, J.A.R., William, A.J., eds., Proceedings of IEEE 6th Working Conference on Current Measurement Technology, pp. 249-253, 1999.
Holdaway, G.P., Thorne, P.D., Flatt, D., Jones, S.E. & Prandle, D., Comparison between ADCP and Transmissometer Measurements of Suspended Sediment Concentration, Continental Shelf Research, 19(3), pp. 421-441, 1999.
Gordon, R.L., Acoustic Doppler Current Profiler: Principles of Operation, RD Instruments, San Diego, USA, 2nd edition, 1996.
Lohrmann, A., Monitoring Sediment Concentration with Acoustic Backscattering Instruments, Nortek Technical Note, Number 003, pp. 5, 2001.
Ghaffari, P., Azizpour, J., Noranian, M., Chegini, V., Tavakoli, V. & Shah-Hosseini, M., Estimating Suspended Sediment Concentrations Using A Broadband ADCP in Mahshahr Tidal Channel, Ocean Science Discussion 8, pp. 1601-1630, 2011.
Merckelbach, L.M., A Model for High-Frequency Acoustic Doppler Current Profiler Backscatter from Suspended Sediment in Strong Currents, Continental Shelf Research, 26, pp. 1316-1335, 2006.
Poerbandono & Mayerle, R., Effectiveness of Acoustic Profiling for Estimating the Concentration of Suspended Material, Die K1/4ste, 69, pp. 393-407, 2005.
Kostaschuk, R., Best, J., Villard, P., Peakall, J., Franklin, M., Measuring Flow Velocity and Sediment Transport with an Acoustic Doppler Current Profiler, Geomorphology, 68(1-2), pp. 25-37, 2005.
Poerbandono, Sediment Transport Measurements and Modeling in The Meldorf Bight Tidal Channels, German North Sea Coast, Dissertation, Christian-Albrechts-Universitat zu Kiel, 2003.
Gartner, J.W., Estimating Suspended Solids Concentrations from Backscatter Intensity Measured by Acoustic Doppler Current Profiler in San Francisco Bay, California, Marine Geology, 211, pp. 169-187, 2004.
Poerbandono & Magetsari R.N., Identification of Representative Erosion and Accretion Patterns Across North Java Coasts on The Basis of Analytical Study of Current and Seabed Interaction, Report, Foundation for Research and Community Services, Institut Teknologi Bandung, 2007.
Poerbandono & Mirza, A., Sensitivity and Accuracy Assessments of Doppler-Type Hydro-Acoustic Current Profilers for Estimating Suspended Particulate Matter Concentration from Field Tests, Proceedings of the 10th SE Asian Survey Congress, Nusa Dua, Bali, 4-7 August 2009.
Kaneda, A., Takeoka, H., Koizumi, Y., Periodic Occurrence of Diurnal Signal of ADCP Backscatter Strength in Uchiumi Bay, Japan, Estuarine, Coastal and Shelf Science, 55, pp. 323-330, 2002.
Lurton, X., An Introduction to Underwater Acoustics: Principles and Applications, Praxis Publishing, Chichester, UK, 2002.
Poerbandono, On the Interpretation of Suspended Sediment Concentration from Acoustic Backscattering Amplitude for Sediment Flux Studies, Proceedings of the 11th International Symposium and Exhibition on Geoinformation, Kuala Lumpur, 25-26 September 2012.