Acoustic communication is one of the most well-known behavioural traits of the Orthoptera. Orthopteran insects and the sounds they produce are both extremely diverse, and speciesspecific sounds are an extremely important tool in orthopteran taxonomy and systematics. For most species, acoustic signalling is the most important means of communication. It plays a vital role in mating, mate choice, intrasexual competition, interspecific interactions with predators and parasitoids, and the divergence of populations and species. The enormous diversity of the orthopterans has provided researchers with a wealth of model systems for studying anatomy, physiology, neurobiology, bioacoustics, communication, life-history traits, behaviour, evolutionary ecology, and speciation, all areas in which acoustic communication is important. We first reviewed orthopteran sound signalling nearly 20 years ago (Robinson and Hall, 2002), since when there has been an enormous amount of further work. This second review will look mainly at research published since that first review.