Oliver C C
Department of Mechanical Engineering, University of Florida, Gainesville 32611.
Semin Perinatol. 1989 Oct;13(5):354-61.
Sound pressure levels measured inside a body must account for the acoustic impedance of the medium in order to obtain information on acoustic intensity. However, there is some uncertainty about the acoustic signals that reach and stimulate the fetal ear. Large wavelengths of frequencies in tissue in the human audible range suggest that the fetal ear will be in the near field of signals transmitted across the air/tissue interface or from an electrolarynx vibrator over a large portion of the frequency range. There are numerous physical mechanisms which effect high-frequency signals in transmission. Vibrational shear waves generated by electrolarynx activation on the skin will influence the fetal sound environment. Further research is required to fully understand the significance of measured signals when both compression and shear waves are present. Data in the frequency domain could be misconstrued, unless peculiarities of some acoustical measuring systems are understood.
在体内测量的声压级必须考虑介质的声阻抗，以便获取有关声强的信息。然而，到达并刺激胎儿耳朵的声信号存在一些不确定性。人类可听范围内组织中频率的长波长表明，在大部分频率范围内，胎儿耳朵将处于通过空气/组织界面传输的信号或来自电子喉振动器的信号的近场中。有许多物理机制会影响高频信号的传输。电子喉在皮肤上激活产生的振动剪切波会影响胎儿的声音环境。当压缩波和剪切波都存在时，需要进一步研究以充分理解测量信号的意义。除非了解某些声学测量系统的特性，否则频域中的数据可能会被误解。
