It is shown that the attenuation coefficient will decrease obviously with the increase of Mach number, and the nonlinear acoustic resistance and acoustic mass will reduce slightly.

研究表明，随着气流马赫数的增加，吸声结构的消声系数明显下降，微穿孔板的非线性声阻和声质量修正值都略有减少。更需注意，在高速流条件下吸声结构的共振峰将会发生偏移。

youdao

So, the echoes from a tree are going to a mass of chaotic acoustic reflections, not like the echo from a moth.

所以，树的回声会是一团混乱的声波反射，而不像飞蛾的回声那样。

youdao

The monitoring technique of rock mass acoustic emission is of wide use in the stope stability. A grey model GM (1.1) for scientific forecasting was presented in this paper.

岩体声发射监测技术已广泛应用于采场稳定性研究中，文中提出了能进行科学预报的灰色GM(1.1)模型。

youdao