Transformations that happen very rapidly frequently emit sound, a phenomenon known technically as "Acoustic Emission". In the course of studies of the transformation behaviour of high carbon steel during cooling from the austenitic condition, Francisca Garcia Caballero discovered that the steel "began to sing".The acoustic emissions occurred reproducibly over a period of about ten minutes as the austenite cooled over the temperature range 200 to 25 oC. Because of the very high carbon concentration of the steel concerned, it is possible that the emissions are caused either by the formation of bainite, martensite or a combination of the two. It would be tremendously exciting if the emissions could be identified to be from bainite because that would indicate a remarkably fast transformation rate. You may download the file from this site. The file can be played on a PC running Windows which usually has a utility for listening to such a file. The file is 5 Mbytes in size. You may download the file from this site. The file can be played on a Sun unix computer with its "audio tool". The file is 1.4 Mbytes in size.