Speech rhythm has been investigated from phonetic, phonological and signal processing perspectives, leading to a wide range of non-comparable methodologies. We assume that this is because speech rhythm is an emergent phenomenon (Emergent Rhythm Theory), due to many 'hidden' physiological and other factors, and that specialists make different selections from these factors. We also claim that models proposed so far are relatively arbitrary, and that their formal and empirical similarities and differences are not clarified. Although we accept Emergent Rhythm Theory, we acknowledge that it is currently too complex and inexplicit to be falsifiable, and concentrate on more highly constrained Physical Rhythm Theory approaches. We propose a set of explicanda for Physical Rhythm Theories, and formally and empirically compare selected single-parameter physical rhythm measures. We find that the selected measures show a very low degree of similarity and outline the steps necessary to improve the situation. 32893292Roach, P., On the distinction between 'stress-timed' and 'syllable-timed' languages (1982) Linguistic Controversies: Essays in Linguistic Theory and Practice, pp. 73-79. , D. Crystal, Ed. London: Edward ArnoldScott, D.R., Isard, S.D., De Boysson-Bardies, B., On the measurement of rhythmic irregularity: A reply to Benguerel (1986) Journal of Phonetics, 14, pp. 327-330Low, E.L., Grabe, E., Nolan, F., Quantitative characterisations of speech rhythm: Syllable-timing in Singapore English (2000) Language and Speech, 43 (4), pp. 377-401Barbosa, P.A., Explaining brazilian Portuguese resistance to stress shift with a coupled-oscillator model of speech rhythm production (2002) Cademos de Estudos Lingüisticos, 43, pp. 71-92Cummins, F., Speech rhythm and rhythmic taxonomy (2002) Proceedings of Speech Prosody 2002, pp. 121-126. , Aix-en-ProvenceGalves, A., García, J., Duarte, D., Galves, C., Sonority as a basis for rhythmic class discrimination (2002) Speech Prosody 2002, , Aix-en-ProvenceRamus, F., Acoustic correlates of linguistic rhythm: Perspectives (2002) Proceedings of Speech Prosody 2002, pp. 115-120. , Aixen-ProvenceRamus, F., Nespor, M., Mehler, J., Correlates of linguistic rhythm in the speech signal (1999) Cognition, 73 (3), pp. 265-292Sândalo, M.F., Truckenbrodt, H., Some notes on phonological phrasing in Brazilian Portuguese (2002) MIT Working Papers in Linguistics, 42Gibbon, D., Computational modelling of rhythm as alternation, iteration and hierarchy (2003) Proceedings of ICPhS 2003, , BarcelonaCorpus-based syntax-prosody tree matching (2003) Proceedings of EUROSPEECH 2003, , GenevaGibbon, D., Gut, U., Measuring speech rhythm in varieties of English (2001) Proceedings of EUROSPEECH 2001, pp. 91-94. , AalborgBarbosa, P.A., Integrating gestural temporal constraints in a model of speech rhythm production Journal of Phonetics, Special Issue: Temporal Integration in the Perception of Speech, 313 (4), p. 54. , ed. Sarah Hawkins & Noël NguyenExplaining cross-linguistic rhythmic variability via a coupledoscillator model of rhythm production (2002) Proceedings of Speech Prosody 2002, pp. 163-166. , Aix-en-ProvenceDuarte, D., Galves, A., Lopes, N., Maronna, R., The statistical analysis of acoustic correlates of speech rhythm (2001) The Sciences of Complexity Conference, , ZiF, BielefeldFrota, S., Vigário, M., Aspectos de prosódia comparada: Ritmo e entoação no PE e no PB Actas Do XV Encontre Nacional da Associação Portuguesa de Lingüistica, 1, pp. 533-555Wachsmuth, I., Communicative rhythm in gesture and speech (2002) Language, Vision and Music, pp. 117-132. , P. McKevitt, C. Mulvihill, and S. Ó'Nuallain, Eds. Amsterdam: John Benjamin