Multi-Site Low-Frequency Spectral Analysis of Environmental Sensor Recordings

This report presents an exploratory comparative spectral analysis of 30 environmental sensor recording sessions acquired across multiple outdoor locations. Using a standardized acquisition workflow and a consistent spectral processing pipeline, the study investigates whether low-frequency environmental sensor recordings exhibit stable and distinguishable site-dependent spectral signatures. The dataset was acquired using smartphone-based motion sensors, with the gyroscope used as the primary measurement source. The analysis includes spectral signature extraction, peak detection, spectral metrics, site-level fingerprint construction, spectral distance computation, principal component analysis, and hierarchical clustering. The results indicate that recordings obtained at the same site are substantially more similar to each other than recordings obtained at different sites. Quantitatively, the average intra-site spectral distance was 0.611, whereas the average inter-site spectral distance reached 4.010, yielding an inter/intra ratio of 6.56. This work should be read as an exploratory methodological field study and preliminary comparative analysis of environmental spectral structure.