still: applies to what is motionless and adds the implication of hush and absence of sound: the dark, ~ night.


quiet: like still, may implies absence of perceptible motion or sound or both, but it is likely to stress absence of excitement or turbulence, and connote tranquility, serenity, or repose: a ~ town.


silent: applies to motion and stir UNaccompanied by sound and carries a strong impression of silence: a submarine equipped for ~ running.


noiseless: also applicable to soundless motion, usually connotes absence of commotion or sounds of activity or movement: a cat slowly advancing on ~ feet.


still: 既无声音也无动作, quiet: 同still,但强调平静休息不激动, silent: 有动作但无声静音(如老电影), n: 和silent相同，less表示没有任何声音或惊动(commotion)。


记忆方法: 首字母联想，SQSN==>ShenQingShengNa，申请声纳-->检测安静物体。