tap: implies making a light blow usually repeated: ~ on the window to attract a friend's attention.  如Gloria was tapping her feet in time to the music格洛丽亚双脚跟着音乐打拍子


knock: implies a firmer blow, sometimes amounting to a pounding or hammering, and a correspondingly louder sound: the messenger ~ed loudly to awaken us.   (pound 1、重击to strike or hit heavily，如Patrick pounded the couch with his fists用拳头猛敲长沙发，如pounding on the door嘭嘭捶门  2、快速跳动to beat, throb, or vibrate with a strong regular rhythm，如her heart was pounding她的心怦怦狂跳 3、捣碎碾碎to crush or grind into powder or paste，如pound the cloves with salt把蒜瓣和盐捣碎)  hammer锤，铁榔头


rap: suggests a smart vigorous striking on a hard surface that produces a sharp quick sound or series of sounds: the chairman ~ped for order.（smart表示聪明时，暗示能胜过常人，这里是形容动作轻快） rap music说唱音乐，快速说唱歌词，也叫快板乐，起源于黑人音乐


trump: implies a solid pounding or beating that produces a dull booming sound: heard the ~ing and banging of carpenters working on the floor below.   （boom低沉有回响的声音隆隆声a loud, deep, resonant sound，如thunder boomed in the sky空中传来隆隆的雷声,如the guns boomed大炮隆隆作响，如'Stop right there,' boomed the Headmaster”站住”,校长用低沉的声音说，另外表示繁荣成长prosperity and growth，如business is booming商业蓬勃发展，如baby boom生育高峰，特别是美国二战后的生育高峰，如baby boomer)


thud: places more emphasis on the sound and often implies the result of something falling or striking rather than of something being struck: heard the severed tree limbs ~ as they fell.


tap轻敲: 指轻轻敲打，常表反复，knock重敲:表示动作更重，声音更大，甚至是重捶，rap快敲:表示轻快的敲击，产生清脆的声音，trump重击: 指沉重打击(solid原指固体)，发出低沉轰隆的声音，thud发出低沉声音: 更强调声音，如下落物打击物的声音，而非被打击物


记忆方法:  1）首字母TKRTT他磕人太疼<==敲打

         2）敲打的意思是打击出声mean to strike or hit audibly.   AUD词根表示听to hear，如audio音频，audible可以听见，inaudible听不见的