Acoustics: Sound Fields, Transducers and Vibration, 2nd Edition

13.20. Time reversal

Imagine that we place a planar array of microphones between a stage and an audience and then make a recording of a performance by musicians on the stage. We assume that the extent of the array is large enough to be considered infinite and that the microphones are small enough and far enough apart not to disturb the sound field produced. We also assume that the ratio of the smallest wavelength to the microphone pitch is large enough not to introduce spatial aliasing. If we play back the recording through an infinite array of either omnidirectional (monopole) or bidirectional (dipole) loudspeakers in place of the microphones (making the same assumptions as with the microphones), we will faithfully reproduce the concert when ...