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.

鉴于方骨（quadrate）与鼓膜（eardrum）存在解剖连接，本研究验证了如下假说：鸟类可通过张开喙部衰减耳部的声音传递，该机制或为自身发声提供额外保护。考虑到雌雄家鸡的发声能力存在显著差异，本研究以家鸡为模型，探究母鸡与公鸡在该声衰减效应上是否存在差异。
为验证上述假说，本研究采用离体（ex vivo）实验方法，借助激光多普勒振动测量法（laser Doppler vibrometry，LDV），在外耳道引入声音的前提下，分别测量喙部闭合与最大张开状态下的镫骨底板（columellar footplate）振动幅度。实验结果显示，公鸡的平均声衰减量为3.5 dB，母鸡仅为0.5 dB。
为证实该潜在保护机制的实际意义，本研究对啼鸣公鸡进行了声学录音：在其耳部附近测得的声压级可达133.5 dB。该鸣叫声的频率成分与家鸡的最高听觉灵敏度区间高度匹配。
研究结果表明，母鸡与公鸡的声衰减量存在小幅但具有统计学显著性的差异。不过，无论是公鸡还是母鸡，实验测得的声衰减量均较小，相较于镫骨肌活动等其他耳部保护机制，其所能提供的有效防护十分有限。