In audio, a very low frequency oscillation often resulting from a positive feedback path in an amplifier system.
在音响设备中出现的振荡频率极低的低频振荡，常因放大系统的正反馈回路引起。
2
The process of each therapeutic or follow-up interview was recorded by color video cameras and high sensitive audio recording system. Meanwhile a self-designed scale was used for feedback.