1.CVC ndi DSP kuchepetsa phokoso:
Ogula akagula mahedifoni a Bluetooth, nthawi zonse amamva CVC ndi DSP ntchito zochepetsera phokoso zomwe amalonda ali nazo polimbikitsa mahedifoni. Ziribe kanthu kuti ndi angati ogwiritsa ntchito omwe adamva zofotokozera, ogula ambiri samamvetsetsabe kusiyana pakati pa awiriwa. Kusiyanitsa, chifukwa chavuto lotereli, timabwera ku sayansi ya awiriwa pansi pa mfundo yogwira ntchito ndi kusiyana.
DSP ndi chidule cha ma signature a digito. Mfundo yake yogwirira ntchito: maikolofoni imasonkhanitsa phokoso lakunja kwa chilengedwe, ndiyeno kudzera muzitsulo zochepetsera phokoso mkati mwa m'makutu, imabwereza kuti ipange phokoso lofanana ndi phokoso lozungulira, lomwe limalepheretsa phokosolo ndipo motero limakwaniritsa zambiri. Zabwino kuchepetsa phokoso.
CVC ndichidule cha Clear Voice Capture. Ndi pulogalamu yamakono yochepetsera phokoso. Mfundo yake ndi kupondereza mitundu yosiyanasiyana ya phokoso lobwerezabwereza pogwiritsa ntchito pulogalamu yoletsa phokoso yomangidwa ndi maikolofoni.
Kusiyanaku motere:
a. pakuti chinthucho ndi chosiyana, teknoloji ya CVC imakhala makamaka ya echo yomwe imapangidwa panthawi yoyitana, DSP makamaka imakhala ya phokoso lapamwamba komanso lotsika kwambiri lakunja.
b. opindula osiyanasiyana, ukadaulo wa DSP umapangitsa kuti ogwiritsa ntchito mahedifoni azipeza ndalama zawo, ndipo CVC imapindulitsa kwambiri gulu lina.
Mwachidule, mahedifoni omwe amagwiritsa ntchito ukadaulo wa DSP ndi CVC wochepetsera phokoso amatha kuchepetsa phokoso la malo akunja akuyitanira, ndikuwongolera kwambiri kuyimba komanso kumveka kwa mahedifoni.
2.ANC kuchepetsa phokoso:
ANC imatanthawuza Active Noise Control, yomwe imachepetsa phokoso. Mfundo yaikulu ndi yakuti njira yochepetsera phokoso imapanga mafunde obwerera kumbuyo ofanana ndi phokoso lakunja, kusokoneza phokoso. Chithunzi 1 ndi chithunzi cham'makutu choletsa phokoso la feedforward. Chip cha ANC chimayikidwa m'makutu. Ref mic (reference maikolofoni) imasonkhanitsa phokoso lozungulira pamakutu. Maikolofoni yolakwika (Mayikolofoni Yolakwika) Imasonkhanitsa phokoso lotsalira pambuyo pochepetsa phokoso m'makutu. Wokamba nkhani amasewera zotsutsana ndi phokoso pambuyo pa kukonza kwa ANC.
Chithunzi 2 ndi chithunzi chadongosolo la ANC, chokhala ndi zigawo zitatu, zolekanitsidwa ndi mizere yodukaduka. Njira yapamwamba kwambiri ndi njira yoyimbira kuchokera ku ref mic kupita ku cholakwika mic, ntchito yoyankha imayimiridwa ndi P(z)P(z); wosanjikiza wapakati ndi njira ya analogi, pomwe njira yachiwiri ndi njira yochokera ku zosinthira zosefera kupita ku zotsalira zobwerera. Kuphatikizapo DAC, fyuluta yomanganso, chokulitsa mphamvu, kusewerera kwa speaker, kupezanso, pre-amplifier, anti-aliasing filter, ADC; wosanjikiza wapansi ndi njira ya digito, pomwe fyuluta yosinthira nthawi zonse imasintha kuchuluka kwa kulemera kwa fyuluta kuti muchepetse zotsalirazo mpaka kulumikizana. Yankho lofala kwambiri ndikugwiritsa ntchito fyuluta yosinthira pogwiritsa ntchito FIR FIR kuphatikiza ndi algorithm ya LMS. Sambani chithunzi 2 ndikupeza chithunzi 3.
Ndiroleni ine ndilankhule mwachidule za mfundo za adaptive fyuluta ndi LMS (Least mean square) aligorivimu, ndiyeno Chithunzi 3. Monga momwe chithunzi 4, kupatsidwa athandizira xx ndi ankafuna linanena bungwe dd, zosinthira fyuluta kusintha coefficients kubwereza kulikonse kuti kusiyana pakati pa zotulutsa yy ndi dd kumakhala kochepa komanso kakang'ono mpaka chotsaliracho chili pafupi kwambiri ndi ziro ndikusintha. LMS ndi njira yosinthira zosefera zosinthika. Cholinga cha LMS ndi masikweya a cholakwika chapompopompo e2(n)=(d(n)−y(n))2e2(n)=(d(n)−y(n))2, kuti achepetse ntchito ya cholinga, Kugwiritsa ntchito kutsika kwa gradient kumapereka njira yosinthidwa ya algorithm. (Lingaliro la algorithmic logwiritsa ntchito kutsika kwa gradient kuti muchepetse cholinga ndikupeza njira yosinthidwa ya parameter yomwe ifunike ndi yofala kwambiri, monga kutsika kwa mzere.) Njira yosinthira ya algorithm ya LMS pogwiritsa ntchito fyuluta ya FIR ndi: w(n+1) ) =w(n)+μe(n)x(n)w(n+1)=w(n)+μe(n)x(n), pamene μμ ndi kukula kwake. Ngati kukula kwa μμ kusinthidwa ndikubwerezabwereza, ndi njira ya LMS ya tsatane-tsatane.
Tiyeni tikambirane Chithunzi 3. Apa chosinthira chosinthira chimatuluka pambuyo pa S(z)S(z) kuti chifanizire ndi zomwe akufuna. S(z)S(z) ipangitsa kusakhazikika. M'mabuku, "chizindikiro cholakwa sichinayende bwino" Pakapita nthawi ndi chizindikiro chowonetsera ", kusinthika kwa LMS kwasweka. (Sindinazindikire tanthauzo lake T__T) Njira yothandiza ndi FXLMS (Filtered-X LMS), yomwe imalola x(n) kulowetsa mu gawo la LMS kudzera pa Sˆ(z)S^(z), Sˆ( z S^(z) ndikuyerekeza S(z)S(z). Cholinga cha FXLMS:
E2(n)=(d(n)−s(n)∗[wT(n)x(n)])2,
E2(n)=(d(n)−s(n)∗[wT(n)x(n)])2,
Choncho gradient=−2e(n)s(n)∗x(n)−2e(n)s(n)∗x(n), pamene s(n)s(n) sichidziwika, ndi kuyerekezera kwake, kotero FXLMS Update formula ndi
w(n+1)=w(n)+μe(n)x'(n),
w(n+1)=w(n)+μe(n)x'(n),
Pomwe x'(n)=sˆ(n)∗x(n)x'(n)=s^(n)∗x(n).
Sefa yosinthira ikasintha, E(z)=X(z)P(z)−X(z)W(z)S(z)≈0E(z)=X(z)P(z)−X(z) ) W(z)S(z) ≈ 0, kotero W(z) ≈ P(z) / S(z) W(z) ≈ P(z) / S(z). Ndiko kunena kuti, kulemera kwa zosefera zosinthira kumatsimikiziridwa ndi njira yoyamba ndi njira yachiwiri ya mahedifoni. Njira yoyamba ndi yachiwiri ya chomverera m'makutu ndizokhazikika, kotero kuti kulemera kwa zosefera zosinthira kumakhala kokhazikika. Chifukwa chake, pofuna kuphweka, ma coefficients olemera a mahedifoni a opanga ena a ANC amatsimikiziridwa pafakitale. Zachidziwikire, kumvetsera kwa foni yam'makutu ya ANC mwachiwonekere sikwabwino ngati chomverera m'makutu cha ANC chokhala ndi tanthauzo lenileni, chifukwa muzochitika zenizeni, phokoso lakunja lokhudzana ndi komwe amamvera m'makutu, kutentha kosiyana ndi zina zotere zitha kukhudza. kuyankha kwa channel ya earphone.
Kutsimikizira kwa Matlab
Lembani kachidindo ka Matlab, pogwiritsa ntchito fyuluta yosinthika ya kukula kwa sitepe ya LMS, zotsatira zofananitsa zikuwonetsedwa mu Chithunzi 5. Pakati pa 0 mpaka 2 kHz, ANC ya feedforward imagwiritsidwa ntchito kuthetsa phokoso loyera la Gaussian, ndipo phokoso la phokoso ndi 30 dB + pafupifupi. FXLMS mulaibulale ya Matlab ndiyokhazikika, ndipo zotsatira zake zimakhala zoipitsitsa.
Q&A
a. Chifukwa chiyani ANC imangokhala phokoso lotsika pansi pa 2 kHz?
Kumbali imodzi, kutsekemera kwamawu am'makutu (kuchepetsa phokoso) kumatha kuletsa phokoso lambiri, ndipo sikofunikira kugwiritsa ntchito ANC kuti muchepetse phokoso lambiri. Kumbali inayi, phokoso laling'ono limakhala ndi nthawi yayitali ndipo limatha kupirira kuchedwa kwa gawo linalake, pamene phokoso lapamwamba limakhala laling'ono laling'ono ndipo limakhudzidwa ndi kupatuka kwa gawo, kotero ANC imachotsa phokoso lapamwamba.
b. Ngati kuchedwa kwamagetsi kuli kwakukulu kuposa kuchedwa koyambirira, kodi magwiridwe antchito angachepetsedwe bwanji?
P(z) kuchedwa ndikochepa, S(z) kuchedwa ndi kwakukulu, monga P(z)=z-1, S(z)=z-2, pokhapokha W(z)=z atha kukwaniritsa zofunikira, osati -zochititsa, Zosafikirika.
c. Kodi pali kusiyana kotani pakati pa Feedforward ANC, narrow-band feedforward ANC, ndi mayankho a ANC?
Mapangidwe a Feedforwad ali ndi ref mic ndi mic yolakwika yomwe imasonkhanitsa phokoso lakunja ndi ma sign otsalira amkati, motsatana. Mayankho ake ali ndi cholakwika chimodzi chokha, ndipo chizindikirocho chimapangidwa ndi cholakwika cha mic ndi zotulutsa zosefera.
Broad-band feedforward ndi dongosolo lomwe tafotokozazi. M'magulu ang'onoang'ono, phokoso la phokoso limapanga jenereta yoyambitsa chizindikiro, ndipo jenereta ya chizindikiro imapanga chizindikiro cha fyuluta yosinthika. Ingogwira ntchito pochotsa phokoso lanthawi ndi nthawi.
Feedback ANC imagwiritsa ntchito maikolofoni yolakwika kuti ipezenso chizindikiro chomwe chimasonkhanitsidwa ndi ref mic mu feedforward dongosolo chifukwa chimangokhala ndi zolakwika. Njirayi simakwaniritsa zolepheretsa, kotero kuti zigawo za phokoso zodziwikiratu zokha, mwachitsanzo, phokoso la narrowband periodic, zimachotsedwa. Zindikirani kuti ngati feedforward sakukwaniritsa choyambitsa, mwachitsanzo kuchedwa pakompyuta ndi yaitali kuposa main channel amawuze kuchedwa, angathe kuthetsa narrowband nthawi phokoso phokoso.
Palinso kamangidwe ka Hybrid ANC komwe kumaphatikizapo zowongolera ndi mayankho. Ubwino waukulu ndikuti mutha kusunga dongosolo la chosinthira chosinthira.
