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 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削弱声音经耳部的传递，这一机制或可作为自身发声时的额外保护手段。考虑到家鸡雌雄个体的发声能力存在差异，本研究针对家鸡探究了该效应在雌雄间是否存在差异。为验证该假说，本研究通过体外（ex vivo）实验，采用激光多普勒振动测量法（laser Doppler vibrometry），分别在喙部闭合与最大张开两种状态下向耳道内导入声音，对柱骨足板（columellar footplate）的振动情况进行测量。公鸡的平均声音衰减量为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，本研究对啼鸣的公鸡进行了音频录制，在其耳部附近测得的声压级为133.5分贝。该发声的频谱范围与家鸡听觉敏感性最高的频段一致。研究结果表明，雌雄个体间的声音衰减量存在微小但具有统计学意义的差异。不过，无论公鸡还是母鸡，实验测得的衰减量均较小，相较于镫骨肌（stapedius muscle）活动等其他保护机制，该途径所能提供的有效防护极为有限。