Speakers of the same language, depending on their familiarity with other varieties of their language, intuitively perceive dialectal, sociolectal, stylistic and idiosyncratic similarities and differences in speed (syllabic duration and tempo), volume (intensity), register (frequency range), melodic patterns (intonation), or rhythm. In this study an attempt is made to determine the acoustic factors that allow this identification. More importantly, the present work provides the necessary tools for a systematic analysis of spoken language. This methodology is applied to a comparative study of the Spanish varieties of Mexico City and Madrid, based on data collected from spontaneous speech.