OCTAVie: Open-source Capture Technology for Animal Vocalization in ultrasonic range.

Ultrasonic vocalizations (USVs) in rodents are a key tool in neuroscience for investigating emotion, social behavior, and disease models. However, commercial recording systems remain expensive and generate massive datasets that require heavy post-processing. We present an open-hardware acquisition chain-from microphone to computer-designed to compute and display sonograms in near real time, thus reducing both storage needs and analysis workload. The system integrates (i) a custom ultrasonic microphone capable of detecting signals up to 100 kHz, (ii) a dedicated analog front-end with band-pass and anti-aliasing filtering, (iii) an Intel® Cyclone V GX FPGA implementing on-board Fast Fourier Transform processing and power calculation, and (iv) a lightweight software interface for data transfer and visualization. All design files, including Printed Circuit Board (PCB) layouts, VHDL codes, and C software, are openly released to ensure reproducibility. Compared to traditional microcontroller-based acquisitions, this architecture reduces raw data storage by more than 50% while maintaining a frequency resolution of ∼0.39 kHz and a temporal resolution of ∼2.5 ms - sufficient to resolve both 22 kHz and 50 kHz USVs. Validated with synthetic signals and experimental recordings, the platform provides neuroscientists with a low-cost, modular, and fully transparent tool for studying ultrasonic communication.