We study scalar field perturbations of a static and spherically symmetric spacetime describing a dyonic black bounce geometry. Depending on the electric and magnetic charges, the spacetime can represent either a regular black hole or a horizonless compact object. We derive the effective potential for massless scalar perturbations and analyze its structure for different parameter regimes. In the black hole phase, the quasinormal mode spectrum is calculated using the Wentzel-Kramers-Brillouin (WKB) approximation and compared with the eikonal formula derived from null geodesics. The two approaches show good agreement in the large multipole limit. When the charge parameters exceed a critical value, the event horizon disappears, and the spacetime becomes a horizonless compact object. In this case, the effective potential develops a characteristic double-barrier structure that forms a trapping cavity for perturbations. The time-domain evolution reveals the presence of the echoes produced by repeated reflections of waves inside this cavity. These results suggest that the dyonic black bounce geometry can naturally generate echo signals without introducing artificial boundary conditions, providing a possible observational probe to distinguish horizonless compact objects from classical regular black holes in gravitational-wave observations.

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• Alternative gravity theories
• Classical black holes
• Gravitational waves
• Quantum aspects of black holes