The treated group consisted of 108 hens (27 hens of each breed, in three replicates of nine hens) exposed to the specific sound stimulus of a tape with a mix of three different noises (truck, train, and aircraft) for 60 min (between 8.00 and 9.00 once), in addition to the background noises, in a total noise level of 90 dB maximum (ranging from 85 to 90 dB; treated group)