Quantitative characterisation of audio data by ordinal symbolic dynamics T. Aschenbrenner, R. Monetti, J.M. Amigó and W. Bunk Eur. Phys. J. Special Topics, 222 2 (2013) 473-485 Published online: 25 June 2013 DOI: 10.1140/epjst/e2013-01853-8