Articles | Volume 2, issue 2
Research article
23 Dec 2014
Research article |  | 23 Dec 2014

An overview of underwater sound generated by interparticle collisions and its application to the measurements of coarse sediment bedload transport

P. D. Thorne

Abstract. Over the past 2 to 3 decades the concept of using sound generated by the interparticle collisions of mobile bed material has been investigated to assess if underwater sound can be utilised as a proxy for the estimation of bedload transport. In principle the acoustic approach is deemed to have the potential to provide non-intrusive, continuous, high-temporal-resolution measurements of bedload transport. It has been considered that the intensity of the sound radiated should be related to the amount of mobile material and the frequency spectrum to the size of the material. To be able to fully realise this use of acoustics requires an understanding of the parameters which control the generation of sound as particles impact. In the present work the aim is to provide scientists developing acoustics to measure bedload transport with a description of how sound is generated when particles undergo collision underwater. To investigate the properties of the sound generated, examples are provided under different conditions of impact. It is considered that providing an overview of the origins of the sound generation will provide a basis for the interpretation of acoustic data, collected in the marine environment for the study of bedload sediment transport processes.

Short summary
The paper deals with the measurement of coarse gravel transport in rivers and coastal environments. Quantifying this bedload is generally challenging. The approach adopted here is to use the acoustic sediment-generated noise, SGN, radiated from the interparticle collisions of the mobile bed material. A theoretical model of the radiated sound due to the collisions is presented, and the results are related to the application of SGN to the measurement of bedload transport and mobile particle size.