The Ivolga train and its unusual sound

The Ivolga (EG2Tv) electric multiple unit named after "Иволга" (Eurasian golden oriole)
The unusual sound of the Ivolga train is due to the operation of inverters—devices that convert direct current to alternating current and regulate the power supplied to the motors. The change in the impulses that the engines receive leads to an unusual sound: when leaving the station, the tone becomes increasingly thinner, and upon arrival, on the contrary, it moves downwards.

192 kHz/32 bit float
Microphones - 2x RODE NT5 (ORTF), RODE NTG-3
Recorder - ZOOM F6