Gridi-Papp Marcos
Section of Integrative Biology C0930, University of Texas, 78712 Austin, Texas, USA.
J Acoust Soc Am. 2008 May;123(5):2895-902. doi: 10.1121/1.2897001.
Frogs and toads mostly call with their mouths shut, unlike many other vertebrates. Sound is generated when air crosses the larynx, but there is no direct airflow to the external environment and radiation occurs at the skin. This study directly compares the acoustic output obtained from euthanized frogs with the mouth open against the output obtained with the mouth closed during activation of the larynx by airflow. With the mouth closed, the vocal sac was inflated and the acoustic energy was concentrated in the same harmonics as in the advertisement call, whereas with the mouth open, energy was spread in a wide range of harmonics. The acoustic output at the dominant frequency was more intense with the mouth closed than with the mouth open. More sound was radiated through the vocal sac and head than through the rest of the body. The spectral differences between open and closed mouth treatments matched the differences observed between natural advertisement calls, produced with the mouth closed, and distress calls, produced with the mouth open. By calling with the mouth closed, treefrogs can potentially produce advertisement calls with the energy concentrated in a narrower frequency range than with the mouth open.
与许多其他脊椎动物不同，青蛙和蟾蜍大多在闭嘴时发出叫声。当空气穿过喉部时会产生声音，但没有直接的气流通向外部环境，声音是通过皮肤辐射出去的。本研究直接比较了在气流激活喉部时，安乐死的青蛙张嘴和闭嘴时的声学输出。闭嘴时，声囊膨胀，声能集中在与广告叫声相同的谐波中；而张嘴时，能量分布在广泛的谐波范围内。在主导频率下，闭嘴时的声学输出比张嘴时更强。通过声囊和头部辐射出的声音比通过身体其他部位的更多。张嘴和闭嘴处理之间的频谱差异与在自然情况下观察到的差异相匹配，即闭嘴发出的广告叫声和张嘴发出的求救叫声之间的差异。通过闭嘴鸣叫，树蛙有可能发出能量集中在比张嘴时更窄频率范围内的广告叫声。
