Submitted to: Journal of the Acoustical Society of America
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/8/2009
Publication Date: 11/16/2009
Citation: Carpenter, W.O., Chambers, J.P., Wren, D.G., Kuhnle, R.A., Diers, J.A. 2009. Acoustic measurements of clay-size particles. Journal of the Acoustical Society of America. 126(6):190-195. Interpretive Summary: Knowledge of sediment concentration is important in the study of streams and rivers. Small particles, such as those in the clay size range, can make up a substantial fraction of the transported material. Acoustic measurements make continuous monitoring of sediment transport possible, without the need for personnel on site at streams during storms, at night, on weekends, etc. The current paper describes measurements of the amount of acoustic signal lost due to various amounts of clay in water. This information will be used to design and calibrate an acoustic system to be used for measurements in the field. As a result of the work, the range for the transmit and receive transducers will be 18 cm, allowing good sensitivity to low concentrations and ability to measure high concentrations of suspended fine particles. This work is a step towards a comprehensive acoustic system for remote, autonomous measurement of both sand and fine particles transported by streams and rivers.
Technical Abstract: Knowledge of sediment concentration is important in the study of streams and rivers. The work presented explores using high frequency (20 MHz) acoustic signal attenuation to measure the concentration of fine sediment particles (0.2-5.0 microns) in a fluvial environment. A small laboratory tank with a pitch-catch transducer configuration measured a 35 dB change in signal level over a wide range of kaolinite and bentonite concentrations (1-14 g/L) over a range of distances (180 mm to 357 mm). The data suggests that a fixed distance of 180 mm between the transducers will be capable of measuring the entire range of concentrations.