The main project page[1] contains links to various papers used to investigate this, including a 3D acoustic ray tracer[2] developed for this.<p>[1]: <a href="https://ascent.aero/project/acoustical-model-of-mach-cut-off/" rel="nofollow">https://ascent.aero/project/acoustical-model-of-mach-cut-off...</a><p>[2]: <a href="https://etda.libraries.psu.edu/catalog/18490zfh5044" rel="nofollow">https://etda.libraries.psu.edu/catalog/18490zfh5044</a>