The distance between the acoustic-emission source and the receiving transducer, and the background noise level are primary factors in selecting a particular frequency band.

Sleep experiments were done in 6 subjects under 3 conditions. ( 1) Quiet, background noise level lower than 45dB ( A);

为探讨在噪声环境中的睡眠防护问题，设计了三种状态的睡眠实验：（1）安静状态，背景噪声低于45dB（A）；

The portion of fiber mask obtained with the high threshold depicts the main character of fiber mask. In order to improve the continuity of mask edge and depress the noise output, the background noise level is evaluated for each image.

通过高阈值计算得到的结果确定了各纤维的轮廓的主要部分。为了提高纤维掩码的连续性以及最大限度地降低噪声输出，本文对图像的背景噪声进行评估。

Thus as the signal level drops, the higher frequencies are progressively more strongly filtered, which also filters the constant background noise level.

也就是说随着信号等级降低，高频声音越来越多被过滤，静态的背景噪音也被过滤。

The background noise level of this instrument under the condition of conducted disturbance and disturbance power test is provided.

讨论了监测待测物使用工况的必要性，给出了电流参量测试仪的传导骚扰和骚扰功率的背景骚扰电平。

Effect of Background Noise Level on Measurement

噪声背景值对噪声监测结果的影响

Exploration and Practice of Applying Task-based Language Teaching to Outside Classroom Activities

任务型教学法应用于英语第二课堂的探索与实践

Using the environment of second class and campus to train cultures quality.

2通过第二课堂和校园文化环境来达到文化素质养成的目的；

Application of multimedia in supplementary class of operative surgery

多媒体技术在手术学第二课堂教学的应用体会

Carrying out Extracurricular Activities in PE to Build up the Students'Health

开展体育第二课堂教学对增强学生体质的作用

An Exploration on Improving English Teaching Under Higher Vocational Features

高职特色下以英语第二课堂活动促进教学的探讨

To Strengthen and Widen Library's Service Function as After-class Classroom

强化和拓展图书馆作为第二课堂的服务功能

Functional Analysis on the Educational Impetus of Extracurricular Activities in College

高校第二课堂活动的教育动力功能分析

Learner Autonomy Theory and Its Implication for English Extracurricular Activities

自主学习理论及其对英语第二课堂活动的启示

Thinking and Practice of Supplementary Classes in Clinical Education

在临床医学教育中有效开展第二课堂教育的思考与实践

About Opening Up the Second Class for Teaching Principle of Machinery

对机械原理课程开辟第二课堂的思考

An Empirical Study of Using Extracurricular Activities for Extending College English Teaching

运用第二课堂活动拓展大学英语教学的实证研究

Applying Extracurricular Teaching Activities to Cultivate Students' Practical Ability

运用第二课堂培养学生实践能力的实践

The Influence of Extracurricular Activities on the College English Classroom Teaching

浅谈第二课堂对大学英语课堂教学的作用

Existing Problems of the Second College English Class and the Countermeasures

大学英语第二课堂存在的问题及对策

Extracurriculum& an Important Way to Cultivate Humanities Quality of Applicable Talents

第二课堂&应用型人才人文素质培养的重要途径