Eckard
Sound may not propagate as light, but I agree your Fig 5 is still relevant. To first deal with light; I'd posted the following to you on Petcho's blog.;
"All lenses consist of a medium, with a refractive plane separating the propagation medium (air) and the lens. The whole tenet of my essay is that we have never understood this, or wrongly assumed otherwise, which is why we cannot unravel observations.
The proof is not only implicit in all optical science but is in the consistent explanation it brings to observations."
The same new fundamental truth applies to sound. If there is no 'matter' then it can't be 'detected'. If there IS matter, then there is an interaction, and transfer of energy, BEFORE transmission to the brain at a given constant speed for analysis. We must consider and absorb that because it is oft forgot in application.
So sound needs an ear drum, or membrane of matter (a 'medium') to vibrate to be detected, agreed? If so, then if the medium is approaching the source, the frequency within the medium (once entered) has increased because the distance between wave peaks has decreased. The speed of propagation within the medium is CONSTANT (precisely as Fresnel's refractive index n is constant for any medium).
Ergo, though we 'measure' the 'observable' which is 'frequency' the frequency has only changed because the WAVELENGTH has changed from air to detector medium.
To REALLY now test your intellect to the limits, there is a second factor apart from relative media v which ALSO changes wavelength, which is relative media refractive index n. If the media are at rest with each other, then only n has an effect. If n is the same then only relative v has an effect.
This brings an entirely new understanding to science which, when consistently applied, resolves all the paradoxes. Unfortunately the familiarity of other assumptions still blinds most people to the true mechanism, so also to the solution.
Feist could not detect the returning signal without a detector made of matter. My figure 4 (sorry for typo, not 5) shows a close-up of the essential asymmetry of charge at the new medium surface electrons where there is lateral motion of the electrons with respect to the waves.
But ponder all the above carefully, and I'll respond fully to your other queries in a new post below.
Best wishes
Peter