1.
And the device is broadcasting a subaudible frequency off any spectrum.
而那些装置在发出一种难以察觉的亚音频声音
2.
Orientation can be difficult to perceive with some shapes or at small sizes, though, so it’s best used as a secondary communication vector.
在某些形状下，或者尺寸较小时，方位是比较难以察觉的，因此它最好作为次要的传达矢量。
3.
Note: in soft rocks extracting fixed protection may leave unsightly damage in the form of a crater.
注意：在岩质松软处取出固定支点时，可能会在对小洞造成难以察觉的损坏。
4.
an insensible change in temperature.
难以觉察的温度变化
5.
be difficult to detect or grasp by the mind.
难以被心理察觉或领会的。
6.
an imperceptible drop in temperature; ~an imperceptible nod; color is unperceivable to the touch.
难以觉察的气温下降；轻轻的点头；颜色是不能被触觉感觉的。
7.
To catch sight of(something difficult to discern).
看见，察觉，辨别看到（很难察觉的）东西
8.
impossible or difficult to perceive by the mind or senses.
感觉不到的或很难觉察的。
9.
Like the sun, the planets shift their positions so slowly that their day-to-day motion is hard to detect.
象太阳一样，行星的飘移非常缓慢，以致它们每天的运动很难被察觉。
10.
It was a gradual change;so gradual that its beginnings were hardly noticed;
这是一种渐进的变化：因为变得非常慢，所以开始时很难察觉；
11.
However the culture is profound and difficult to percept, it is very difficult to measure.
但由于文化深层次的难以察觉性，所以对其进行测度又是相当困难的。
12.
in an imperceptible manner or to an imperceptible degree.
以觉察不到的方式；或达到觉察不到的程度。
13.
We are not aware of the travel of light, because it moves at the incredible speed of about 186,000 miles per second.
我们觉察不到光的运行，因为光以秒钟186000英里这个令人难以置信的速度运行。
14.
No man can play the fool so well as the wise man.
智者扮傻瓜，世人难觉察。
15.
The curved needle of the machine ensures that only a fraction of the main garment is caught, therefore allowing the stitch itself to be almost inconspicuous.
这种机器所使用的弯曲的针保证只勾住了衣服上的一小部分,因此使得线迹本身难以被察觉。
16.
his white waistcoat displayed his expansive noble chest and his black stock was singularly noticeable because of its contrast with the deadly paleness of his face.
他唯一的装饰虽是一条极其精致的金链，挂在他白背心上让人难以觉察。
17.
Here were these two, bandying little phrases, drawing purses, looking at cards, and both unconscious of how inarticulate all their real feelings were.
就是这两个人，交换短短的语句，掏荷包，看名片，却都没有觉察到他们的真情是多么难以捉摸。
18.
The film was edited by a skilled technician so that the joints are imperceptible.
这部影片是由一位技术熟练的技术人员剪辑的,因此连接处难以觉察。