Baby's first infrasound. My DIY #Infrasound experiment just produced a strong spectral feature at 3.95 Hz using a Sensirion SDP810 differential-pressure sensor + #ESP32. Did I detect a nearby train? A resonance/artifact from my 15' tube? Something else? I don't know yet -- which means it's time for more experiments. https://salemdata.net/johnpress/?p=1268 #DIY #CitizenScience #Acoustics #Sensors #OpenHardware #DataCenters