Under the overpass (EM and ST amb)

Description

this is a stereo field-recording with a third channel of electromagnetic activity. Ambience under an urban highway overpass near train tracks. The metal thuds you hear are vehicles above. Also an electric saw in the distance. The EM screeching comes from the train tracks, as it is powered by electricity. Zooming into the spectrogram you can see it is actually a 3 tone pulse with lots of harmonics. Recorded on a MixPre6 with LOM Usi Pro microphones and a DIY passive magnetic antenna.