More Mural from Utrecht

Tomorrow this city celebrates it's a city with city rights since 900 years.

Having my grandson in school I walked a little thro' the city and found this mural from the same artists "De Strakke Hand" (the focussed hand) who painted this scene of the Dopplereffect. 
In 1845 the scholar Buys Ballot prooved with brass music players playing their insturments on an open wagon of a train the effect that the tone of sounds get higher when it approaches you and gets lower when it passed by from you. 

Listen to the sound of a nearing and passing by ambulance or police-car with its sirene on... you'll notice this effect what was described in 1842 by Christian Doppler from Austria and as you can tell from this mural in 1845 it was practically proven in Utrecht by Buys Ballot to the people who stood by the railroad and were asked to note down how they heard the tones of the sound that neared them raise and passing by from them lowered... the Dopplereffect proven, that is the "waves" in sound!

June already! Another month starts... Happy new month to you all! Καλο Μηνα σας! 
and thank you for your lovely reactions upon grandson's rosy ear(s)... as you noticed: so sweet :-) 

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