In 2018, these varying origins of the railway network of São Paulo’s metropolitan region – with their unique characteristics of structure, architectures, and public – motivated the creation and execution of the project R$4.00. The initial question was: what are the soundscapes of the railway network? Are there sonic differences between the acoustic workings of trains as compared to subways, or might there even be differences between different lines on the same type of transportation? The project was structured to occur in two different stages. The first was a study in which the author, with an audio recorder, travelled uninterruptedly across the network of subway and train lines of the Greater São Paulo Area. The idea was to try to travel for as long as possible, paying for only one ticket (R$4.00 at the time) and without repeating any of the lines, eventually returning to the initial station. The longest possible combination is shown in Figure 2: 55 stations on 10 different lines.
The audio recording was made all in one go across the train network, with the goal of registering, and later studying, the carriages’ internal environments, noises, conversations, sounds as well as the changes that took place during the more than three hours of movement (Figure 3 shows the sound capture during the process. The recording was made with a Zoom H2n Hand Recorder, using the two channels surround mode (which mixes the signals from mid-side and XY microphones), to spatially capture the sound environment.)
Afterwards, the raw audio was edited so that all movements captured within the carriages were preserved, eliminating the author’s moments of movement between platforms and lines. Thus, the registration becomes a non-stop journey lasting 3 hours and 28 minutes.