unperceivable

1. 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。
2. This algorithm has good performance: Watermark embedded in the image is unperceivable;
   该算法具有很好的性能：水印的隐藏效果好，凭人眼无法看出与原图像的差别；
3. TEM field is slowly changing in middle to deep depth prospecting, which is characterized by unperceivable wave and dominant dissemination, thus it can be assumed to be quasi-static state approximate and the wave equation of electromagnetic wave radiation is retrogressive and replaced by diffusion equation.
   在中、深层勘探情况下，TEM场是缓变的，其波动性已经很不明显，扩散特征起支配作用，波动方程退化成了扩散方程。
4. Experimental results show that the quality degradation of the carrier audio is unperceivable, and the quality of the recovered speech is satisfying.
   仿真结果表明，隐藏有保密语音的载体音频听觉质量没有明显下降，提取的保密语音感知质量较好；

adj

1. impossible or difficult to perceive by the mind or senses
   1. an imperceptible drop in temperature
   2. an imperceptible nod
   3. color is unperceivable to the touch

   Synonym:    imperceptible