Let us consider a spherical cavity of radius $R$ and a point-like source of field at its center.
In the following I will use the jargon of acoustics, but I think that one can think of the propagation of electromagnetic waves, or any other field.
Let us assume that the membrane of the loudspeaker oscillates at a frequency $f$ and that the speed of sound of the medium within the sphere -say air- is $c$. See attached picture.
Let us further assume that the spherical shell is perfectly reflecting.
I am wondering what happens upon changing the ratio $\lambda/R$. In particular: what happens if $\lambda > R$? Can the loudspeaker radiate sound in the medium? Can the energy be transferred from the loudspeaker to the medium? How is -qualitatively- the pressure field in the medium: flat, a complex time-dependent interference pattern, or localized around the loudspeaker (as evanescent fields in electromagnetisms)?
