Data from: Sound attenuation in the ear of domestic chickens (Gallus gallus domesticus) as a result of beak opening

Because the quadrate and the eardrum are connected, the hypothesis was
tested that birds attenuate the transmission of sound through their ears
by opening the bill, which potentially serves as an additional protective
mechanism for self-generated vocalizations. In domestic chickens, it was
examined if a difference exists between hens and roosters, given the
difference in vocalization capacity between the sexes. To test the
hypothesis, vibrations of the columellar footplate were measured ex vivo
with laser Doppler vibrometry (LDV) for closed and maximally opened beak
conditions, with sounds introduced at the ear canal. The average
attenuation was 3.5 dB in roosters and only 0.5 dB in hens. To demonstrate
the importance of a putative protective mechanism, audio recordings were
performed of a crowing rooster. Sound pressures levels of 133.5 dB were
recorded near the ears. The frequency content of the vocalizations was in
accordance with the range of highest hearing sensitivity in chickens. The
results indicate a small but significant difference in sound attenuation
between hens and roosters. However, the amount of attenuation as measured
in the experiments on both hens and roosters is small and will provide
little effective protection in addition to other mechanisms such as
stapedius muscle activity.