Two experiments explored the effects of specific sound stimuli on laying hens.
The first measured heterophil to lymphocyte ratio and tonic immobility duration in 216 36-week-old hens exposed to specific noise stimuli of 65 dB (background chicken vocalizations and fans, control) or 90 dB (background noises plus truck, train, and aircraft noises) for 60 minutes. The measurements showed that the hens exposed to 90 dB noise were more stressed and fearful than control hens.
The second experiment measured heterophil to lymphocyte ratio and tonic immobility duration in 108 36-week-old hens exposed to background noises (65 dB) or to classical music plus background noises (75 dB) between 9.00 and 14.00 for three days. The measurements showed that the hens exposed to classical music were more fearful than control hens.
Overall, the results indicate that loud noise causes stress and fear in laying hens, and classical music influences their fearfulness.
This according to “Effects of specific noise and music stimuli on stress and fear levels of laying hens of several breeds” by José Luis Campo Chávarri, et al. (Applied animal behavior science XCI/1–2 [May 2005] pp. 75–84. Below, Ravel’s orchestration of Musorgskij’s Балет невылупившихся птенцов (Ballet of the unhatched chicks).