????????????????????
1????????繦??
2???迹
3?????????
4??????г??
5????????????????????????
6?????衢??к???????????????????
7?????
?????????????10??50W??87dB/W/m???????10??50 90dB/W/m??????????????????????????????10Hz??40kHz?????????20Hz??20kHz??0.2dB?????????????????????"???(dB)"????к??壬????????????????
????????????????????????λ?????????????????????????????λ??"??"????10?????????100???????????????"???"????λ????????????????棬???????????????????
????з???????????????????
AV(I)(dB)=20lg[Vo/Vi(Io/Ii)]??Ap(dB)=10lg(Po/Pi)
???????????(????)??????????????????????????????????????????????????P=V2/R=I2R??????????????????????????????????
10lg[Po/Pi]=10lg(V2o/R)/(V2i/R)=20lg(Vo/Vi)
??÷??????λ?????3??????
1???????С????д????
????????????????????????????????????????????????????????????????????????????????????2????????÷?????????????????????С???????????????????????????
?????????????????
???(????)????? 1/10 1/
1/2 1
2 10 100 103 104 105
????(dB) -20 -6 -3 0 3 6 20 40 60 80 100
???????? 1/10 1/
1/2 1
2 10 100 103 104 105
????????(dB) -10 -3 -1.5 0 1.5 3 10 20 30 40 50
2????????
?????????????????????????????÷??????λ????????????????????????????100??(20dB)??????20??(13dB)????????????????100??20=2000???????????20dB??13dB=33dB??
3?????????У???????
????????????????????????????????????????磬???繦???0.1????????1.1??????????????????????????1???????2????????????????10???????11??????????????????????????????ù???????????????1?????????????????10.4dB??3dB??0.4dB???????????μ?????????????????????????????????????Hi??Fi????????????????????????????????????????Щ??
???????У???3dB??0dB??????????????????3dB??а???????????????????????????????????????????????1/2??????????У???3dB?????????????????????????????豸?????????Χ????????????????????????????С?3dB????????磬??????????10Hz??40kHz?????????????????У???????????????3dB??????????10Hz??40kHz????????????????????????????м????ε?0.707(1/ )?????0dB????????????????????????????
????????????С????????о??????????????????????·?????????????????????dB???????????????????0dB????????????????????????0dB??2??10??4??b(???)????????·?????????50dB??60dB????????????????
?????0dB????????漸???dBFS????????????????0dB??????????????????????dBm??????600???????????1mW????(??0.775V???)?0dB????????????????????????dBV??????1???0dB??dBW??????1???0dB??
??????????dB?????????????????????????????????????????????????????????????????????????????10A/20(??A/10)??D0?????ɡ?A??????????????D0?0dB????????????????????????A/20???繦?????????????????A/10??
???????????????????????????????????????????????????????????????????????????????????????????????????????????ɡ?????????????????????????????????Hi??Fi??????????Χ??????????С?2.3??????!
????????в??÷????????????
1???????????????=10lg??P1/Po??dB ???????Po=1W
2??????????????=20lg??U1/ Uo??dB ??????Uo=775(dBmV)??Uo=1 ??dBV??
3???????????????=20lg??I1 / Io??dB ???????Io=1(dBmA)??Io=1 ??dBA??
4???????????????SPL??=20 lg(pre1/preo) dB ????????preo=20??10-6N/m2??????1KHZ-3KHZ???????????
5??????????????????????=20lg??R1 / Ro??dB ???????Ro=1m
???к????????÷?????λ????????磺?????????????????????????????????????Χ?????????????????20??
8???????
??????????Щ?????????
1) ??????? ????????????????????????书???????????????
2) ????
3) ??????????? ???????????????ε???????С??1 dB?????????????ε????????????????
9????????????·???
???????????????????????????0.5??dB??10%??
1?????迹??????·??????????
???迹??????????迹????????????????迹??????????????16???????????????????·???????????·?????????????С??????????????????????????·????????????????y???????????????Ч????д??????????????????????
????????dB??=20 lg??RL/ 2R1+ RL??
R1=??L/S
20????? ??=0.0159 ?=0.0172 ??=0.0282
2?????迹???????????????·???????????
????????????У?????????????????????????????????????·??????????????200M????????????????????????迹??????·?????????????????????????????????????????????????????迹/??????????50V??70V??100V???????????????????????????????????·?????????????????????????????????????????????????????????
??·????10%???
???迹?????????????S???
S?R??0.37??L??P??/U2
???迹?????????????S???
S?R??0.37??L??/Z
L???????
P???书??
U?????????????
Z????????????迹
3???????????????????????迹???
????????????и???????????????????
??
?迹 ???? Ч ?? ???
Z??SP??=Z??AMP??P??SP??= P??AMP?? ?????????????????????? ???
Z??SP??>Z??AMP??P??SP??= P??AMP?? ?????????????????????????????? ?????????????
Z??SP??
Z??SP??= Z??AMP??P??SP??> P??AMP???????????????????????????????? ???????
Z??SP??= Z??AMP??P??SP??< P??AMP????????????
Z??SP??= Z??AMP??P??SP???? P??AMP?? ??????????????????????????????????????????????????
100V????????е?????1 dB????????????????m
???????? ???书??
/mm2 4 10 20 40 100 200 400 1000
0.3 2500 1000 500 250 100 50 25 10
0.5 4000 1600 800 400 160 80 40 16
0.75 6000 2400 1200 600 240 120 60 24
1.0 8000 3200 1600 800 320 160 80 32
1.5 12000 4800 2400 1200 480 240 120 48
2.5 20000 8000 4000 2000 800 400 200 80
4.0 32000 12800 6000 3200 1280 640 320 128
6.0 48000 19200 9600 4800 1920 960 480 192
???????
