VAD（话音活动检测）/DTX（不连续传输）/CNG（舒适噪音生成）主要应用在不活跃的语音周期中，降低传输速率，同时保持可接受的输出质量。VAD将输入信号分类为活动语音、非活动语音和背景噪声。基于VAD决策，DTX在静默期间插入静默插入描述符（SID）帧。在静默期间，SID帧被周期性地发送到CNG模块，该模块在接收端的非活动语音期间产生环境噪声。提升用户体验，防止用户误认为通话已结束。
VAD (Voice Activity Detection) / DTX (Discontinuous Transmission) / CNG (Comfort Noise Generator) are used to reduce the transmission rate during inactive speech periods while maintaining an acceptable level of output quality. VAD classifies the input signal into active speech, inactive speech or background noise. Based on the VAD decisions, DTX inserts Silence Insertion Descriptor (SID) frames during the silence intervals. During silence, SID's are periodically sent to the CNG module, which generates ambient noise during periods of inactive speech on the receive side.