Larger regions are often acoustically irradiated with a plurality of loudspeakers. A public address system 1 for the sonication of a sonication region 2 is proposed, wherein the public address system has a multiplicity of loudspeakers 3a, 3b, wherein the loudspeakers 3a, 3b are arranged in the sonication region 2 are designed to output an audio signal based on an input signal 4a, 4b. The public address system has a measuring device 5 for the detection of the audio signal at a measurement point 6 in the sonication region 2, wherein the measuring device 5 is designed to determine a propagation time difference Δtn of the audio signals to the measurement point 6 between each of two speakers 3a,b and to provide the propagation time difference Δtn as propagation time difference data.