And yet machines at present cannot truly hear. Apart from well-developed efforts to recover structure in speech and music, the state of the art in machine hearing is limited to relatively impoverished descriptions of recorded sounds: detecting occurrences of a limited pre-specified set of sound types, and their locations. Although researchers typically envision artificially intelligent agents such as robots to have human-like hearing abilities, at present the rich descriptions and inferences humans can make about sound are entirely beyond the capability of machine systems. 
