The Voice of a SODAR/RASS

Maybe you read in Servizi Territorio's site of the SODAR/RASS, and discovered it's an acoustic remote sensor. But then, what its "voice" is? Here you may find one example.


Patrizia Favaron

12/6/20221 min read

The SODAR (SOund Detection And Ranging) is an acoustic sensor for probing wind velocity along a vertical path. The RASS extension is a combined acoustic-radio sensor measuring temperature along the same direction.

They have both an acoustic nature, and them, well, they emit sounds... I have to add the loudness of these sounds if very high, and would it not be for sound suppression shield the lateral impact would be really untenable. The sound suppression shield exists however, so no direct harm is possible. Some noise is emitted however, and this (static) video allow you to get an idea.

You will notice a structure: three "low frequency" pulses, then one "high frequency". The first three pulses sample wind along three directions: the vertical, and two slightly tilted directions pointing towards North and West respectively.

The recording has been performed using a Rode NTG-3 "shotgun" microphone, positioned right above the "unsafe" zone, inside the sound suppression barrier. The actual sound capture was performed using a Zoom F3 professional field recorder, running at 196 kHz and operated in 32 bit floating point mode. No acoustic clean-out was made between any two consecutive pulses: it is then possible you hear plant-related noise in the in-betweens.