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）相连，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，这一机制或可作为针对自身发声的额外保护手段。考虑到家鸡雌雄个体的发声能力存在差异，本研究针对母鸡与公鸡是否存在该效应差异展开了考察。为验证上述假说，本研究通过离体实验，采用激光多普勒振动测量法（laser Doppler vibrometry，LDV），在耳道内引入声音的前提下，分别测量喙部闭合与最大张开状态下的镫骨底板（columellar footplate）振动情况。实验测得公鸡的平均声衰减量为3.5分贝，母鸡仅为0.5分贝。为证明该推定保护机制的重要性，本研究对打鸣公鸡的发声进行了录音，结果显示其耳部附近的声压级可达133.5分贝。该发声的频率范围与家鸡听觉灵敏度最高的频段相符。研究结果表明，母鸡与公鸡在声衰减方面存在小幅但显著的差异。不过，无论公鸡还是母鸡，实验测得的声衰减量均较小，相较于镫骨肌活动等其他保护机制，该手段所能提供的有效防护极为有限。