Transient study of an optimized waveguide sonic black hole with wave focusing properties Hamideh Hassanpour Guilvaiee, Abbas Mousavi, Martin Berggren, Eddie Wadbro, Manfred Kaltenbacher and Florian Toth Acta Acust., 9 (2025) 36 Published online: 11 June 2025 DOI: 10.1051/aacus/2025019