Publication titles, authors, and sources are listed rather than links to them. Links often disappear but the other information can always be used to find the references.
Helmholtz effects at the intake runner ends were ignored during engine development until now. The air filters were attached to the carb ends. There was little plenum resonance effect from them. The sides were pleated oiled fabric and metal screens. This is very good at wave absorption rather than reflection and Helmholtz resonance was negligible.
Bell mouths are on the carb ends now. Packaging considerations require some sort of enclosures around those bell mouths ends if air cleaners will be used. The centerlines of the filters and bells are offset and the enclosures are the transitions between the two. The transitions are plenums and Helmholtz resonance will occur in those cavities. This could hurt, help, or do nothing for performance. At the minimum, I need to learn enough about the process to verify that the resonance is not causing problems. Better yet will be using it to improve performance.
The Helmholtz design process is described in American Society of Mechanical Engineers (ASME) Paper 73-WA/DEP-2, by H.W. Engleman, "Design of a Tuned Intake Manifold" Manifold design using this method is described in International Journal of Scientific Technology Research , Issue 5, May 2014, by Shirinath Potul, Rohan Nachokar, Sagar Bheve "Analysis of Change in Intake Manifold Length and Development of Variable intake System."
That last publication describes software to figure out this stuff from Lotus Engineering in the UK. This might be helpful. The boost bottle concept is something I know about and have used. It will be the subject of a future post.