Universiteit van Amsterdam, Spuistraat 210, 1012 Vermont Amsterdam, The Netherlands. mail:
J Acoust Soc Am. 2009 Dec;126(6):3329-43. doi: 10.1121/1.3257544.
This paper presents an analysis of the acoustic impedance of primate air sacs and their interaction with the vocal tract. A lumped element model is derived and it is found that the inertance of the neck and the volume of the air sac are relevant, as well as the mass and stiffness of the walls (depending on the tissue). It is also shown that at low frequencies, radiation from the air sac can be non-negligible, even if the mouth is open. It is furthermore shown that an air sac can add one or two low resonances to the resonances of the oral tract, and that it shifts up the oral tract's resonances below approximately 2000 Hz, and shifts them closer together. The theory was verified by acoustic measurements and applied to the red howler monkey (Alouatta seniculus) and the siamang (Symphalangus syndactylus). The theory describes the physical models and the siamang calls correctly, but appears incomplete for the howler monkey vocalizations. The relation between air sacs and the evolution of speech is discussed briefly, and it is proposed that an air sac would reduce the ability to produce distinctive speech, but would enhance the impression of size of the vocalizer.
本文分析了灵长类动物气囊的声阻抗及其与声道的相互作用。推导出了一个集总元件模型，发现颈部的惯性和气囊的体积以及壁的质量和刚度（取决于组织）是相关的。还表明，在低频下，即使口腔张开，气囊的辐射也可能不可忽略。进一步表明，气囊可以在口腔声道的共振中增加一个或两个低共振，并且将口腔声道的共振向上移动到大约 2000 Hz 以下，并使它们彼此更接近。该理论通过声学测量得到了验证，并应用于红吼猴（Alouatta seniculus）和合趾猿（Symphalangus syndactylus）。该理论正确地描述了物理模型和合趾猿的叫声，但对于吼猴的叫声似乎并不完整。简要讨论了气囊与语言进化的关系，并提出气囊会降低产生独特语音的能力，但会增强发声者的大小印象。
