The mirror effect for sound waves can be observed particularly well with very long and wide sewage pipes. When you sing or talk right in front of the open end of such a pipe, you will hear your voice reflected on the open end of the pipe.
Yet your voice can be heard at the other end of the pipe too. The resonance frequency of such pipes is so low that it doesn't play any role in the sound of your voice: apart from being reflected, the sound also travels to the other end of the tube. A similar effect occurs in wind instruments only with a squeaking reed, in which case the reed is a source of sound by itself and its vibration is not controlled by the length of the tube (as it in normal use: the vibration of the reed will be controlled by the resonance frequency of the tube).