Mobile sound source. The length of the wave out to the front of the sound source is shorter. Best wavelength of the source voice that moves through the very long wavelength.
Moving sound source Wavelength at the front of the sound source is shorter. Behind the wavelength of the sound source moving through. The longer wavelength
The sound source is moving. Wavelengths out in front of the sound source will be shorter. The wavelength of the sound source moving back pass. A long wavelength.