The Doppler Effect is a phenomenon that explains the apparent change in siund frequency to an observer.
The observers hear different frequency in relation to their position to the source, but the source's frequncy does not
change.
c= sound speed through a medium= 343 m/s at 20 degrres C
o= observer and s= source
V= 331 + .6T= sound formula where T is the temperature.
Add when the source is moving away from the observant, but subtract when it is moving towards you.