As they grow, children get little by little independent. The MOBIKIDS1 research aims to study how children's mobility and spatial experiences evolve during the transition from elementary school to secondary school. The first objective was to understand the social, psychological and spatial conditions for the evolution of urban practices by describing forms of urban educational culture (UEC) and the role of routines and informality in these practices. A part of the methodology was based on the "Commented city walk2" developed by JP.Thibaud and revised here with children. Thus, with children who consented, it consisted in collecting children’s voices and photos (video-recording in the second year) taken by them during the commented walk made in a familiar context (school-home journey). More precisely,this was to make the return journey from school and to ask the kid to describe his/her perceptions, sensations & other observations during the travel. This walk & comments were recorded in situ, then transcribed to help with the various forms of analysis afterwards. But, as a matter of principle, these transcriptions only preserve what is in the order of speech in the expression of the children during their journey. But this expression is much richer and more subtle than the simple words they use. It is expressed through the voice, its intonations, its rhythms, its hesitations or silences sometimes, it is expressed through the relationships that we hear between the child walking and the sounds of the environment, or with the investigator who accompanies and questions him. It is therefore to an analysis "by ear" that I'll try to explain & to share with you, with a few examples of how to recompose those recordings. Mainly 7 categories have made out of them: (- relationship to the environment) (- interactions with the interviewer) - melodic voice expressions - monosyllabic expressions - hesitations - speech adjustments - verbal expressions