“…In the first class, also known as compounding techniques, multiple uncorrelated recordings are averaged. Techniques in this class include spatial compounding (Avanaki et al (2013)), angular compounding (Schmitt (1997)), polarization compounding (Kobayashi et al (1991)) and frequency compounding (Pircher et al (2003)). As for post-processing techniques, anisotropic diffusion based methods (Salinas and Fernández (2007), Puvanathasan and Bizheva (2009)), multiscale/multiresolution geometric representation based techniques (Pizurica et al (2008), Adler et al (2004), Jian et al (2009, 2010), Guo et al (2013), Xu et al (2013), Gupta et al (2014)) and compressive sensing and sparse representation based approaches (Fang et al (2012, 2013)) are good examples.…”