BO CO TIN N CHUYN NGNH Ngi thc hin : ng Minh ChThi gian: t 21/03/2013 n 10/04/2013

I.m thanh v c trng ca m thanh1.Mt s khi nimTn hiu m thanh ni chung nh l tn hiu m c th nghe r t ngi. Cc tn hiu ny thng n t b ngun m thanh m cc rung ng trong dy tn s m thanh. Cc rung ng ny y vo khng kh to thnh sng p sut khong 340 mt trn giy. Tai trong ca chng ta c th nhn c cc tn hiu p sut ny v gi chng n no nhn dng. Tn hiu m thanh thc s i din cho p sut khng kh nh l mt hm ca thi gian, m lin tc trong c thi gian v bin tn hiu. Khi chng ta mun s ha tn hiu lu tr trong my tnh, c vi tham s cn phi xem xt:- T l ly mu: l s im mu tn hiu trn mt giy, theo n v Hz. T l ly mu cao cho ra m thanh tt, nhng khng gian lu tr ln. Cc t l thng s dng: 8kHz: cht lng m thanh cho in hay chi 16kHz: s dng cho nhn dng ting ni. 44.1kHz: cht lng a CD- S bit phn gii (Bit resolution): s bit s dng biu din cho mi im ca tn hiu m thanh. Cc thng s thng c s dng: 8-bit: tng ng vi dy 0~255 hoc -128~127 16-bit: tng ng vi dy -32768~32767.Ni cch khc, mi mu tn hiu c biu din bi mt s nguyn ca 8 hoc 16bits. Tuy nhin trong Matlab, tt c tn hiu m thanh c chun ha n s im thc (float-point) trong dy [-1,1] d thao tc. Nu bn mun chuyn i cc gi tr s nguyn nguyn gc, bn cn phi nhn vi gi tr 2nbit/2, trong nbits l s bit phn gii.- Knh: mono v stereo.Ly mt file xinchao.wav lm v d, c thu m mono vi t l ly mu 16000(16kHz) v s bit phn gii 16bit (2byte) v cng cha 15716 im mu tng ng vi thi gian ghi m l 15716/16000 = 0.98 giy. Do , dung lng ca file khong 15716*2 = 31432 = 31.4KB. Thc t, dung lng file lu tr tn hiu m thanh l hi ln, c th: Nu chng ta s dng cc tham s tng t nh trn thu m trong 1 pht dung lng file s l: 60*16kHz*2Byte=1920KB ~ 2MB. i vi m thanh trong CD, chng ta ghi m ch stereo vi t l ly mu 44.1kHz, phn gii bit l 16, trong vng 3 pht dung lng file l: 180*44.1kHz*2byte*2= 31752Kb = 32MB2.c trng ca m thanhKhi phn tch tn hiu m thanh, chng ta thng p dng phng php phn tch ngn hn, do hu ht tn hiu m thanh n nh nhiu hoc t hn trong khong thi gian ngn, chng hn 20ms. Khi thc hin phn khung, c th s dng nhiu khung chng lp nm bt s thay i tinh t ca tn hiu m thanh. Lu rng mi khung l mt n v c bn phn tch tn hiu. Trong mi khung, chng ta c th quan st ba tnh nng m hc khc bit nht, nh: m lng (Volume): tnh nng ny i din cho ln (loudness) ca tn hiu m thanh, tng quan vi bin ca tn hiu. Thnh thong, n cng c cp n nh nng lng hoc cng ca tn hiu m thanh. cao (Pitch): tnh nng ny i din cho t l rung ca tn hiu m thanh, m c th biu din bi tn s c bn hoc tng ng, nghch o ca chu k c bn ca tn hiu ting ni. m sc (Timbre): c trng ny i din cho ni dung ng ngha (chng hn mt nguyn m trong ting Vit) ca tn hiu m thanh, m c c trng bi dng sng trong mt chu k c bn ca tn hiu ting ni.Ly ting ni ngi lm v d, ba tnh nng trn lin quan n mt vi c im vt l: m lng: lin quan n nn ca phi. m lng cao ca tn hiu tng ng vi nn ln. Cao : lin quan n tn s rung ca dy thanh m. Cao cng cao tng ng vi tn s rung ln. m sc: lin quan n v tr v hnh dng ca mi v li. m sc khc nhau tng ng vi v tr v hnh dng khc nhau ca mi v li.II.Tng quan v nhn dng ting ni 1.Tng quan v nhn dng ting ni Nhn dng ting ni l mt qu trnh nhn dng mu, vi mc ch l phn loi( classify ) thng tin u vo l tn hiu ting ni thnh mt dy tun t cc mu c hc trc tr trong b nh. Cc mu l cc n v nhn dng, chng c th l cc t, hoc cc m v. Nu cc mu ny l bt bin v khng thay i th cng vic nhn dng ting ni tr nn n gin bng cch so snh d liu ting ni cn nhn dng vi cc mu c hc v lu tr trong b nh. Kh khn c bn ca nhn dng ting ni l ting ni lun bin thin theo thi gian v c s khc bit ln gia ting ni ca nhng ngi ni khc nhau, tc ni, ng cnh v mi trng m hc khc nhau. Xc nh nhng thng tin bin thin no ca ting ni l c ch v nhng thng tin no l khng c ch i vi nhn dng ting ni l rt quan trng. y l mt nhim v rt kh khn m ngay c vi cc k thut xc sut thng k mnh cng kh khn trong vic tng qut ho t cc mu ting ni nhng bin thin quan trng cn thit trong nhn dng ting ni. Cc nghin cu v nhn dng ting ni da trn ba nguyn tc c bn:- Tn hiu ting ni c biu din chnh xc bi cc gi tr ph trong mt khung thi gian ngn (short-term amplitude spectrum). Nh vy ta c th trch ra cc c im ting ni t nhng khong thi gian ngn v dng cc c im ny lm d liu nhn dng ting ni. - Ni dung ca ting ni c biu din di dng ch vit, l mt dy cc k hiu ng m. Do ngha ca mt pht m c bo ton khi chng ta phin m pht m thnh dy cc k hiu ng m.- Nhn dng ting ni l mt qu trnh nhn thc. Thng tin v ng ngha (semantics) v suy on (pragmatics) c gi tr trong qu trnh nhn dng ting ni, nht l khi thng tin v m hc l khng r rng.2 . Quy trnh to lp ting ni ca ngi nhn dngQuy trnh to lp ting ni ca ngi nhn dng bao gm cc bc sau:1. M v ng nhanh dy thanh m hoc thanh mn (glottis) to rung ng trong lung khng kh.2. Cng hng ca khoang yt hu, khoang mi v khoang ming.3. Rung ng ca khng kh.4. Rung ng ca trng tai hoc mng nh (tympanum).5. Thu nhn ca tai trong6. Nhn dng bi b no Cng vi p lc ca thanh mn v khng kh y ln t phi, dy thanh m c th m v ng rt nhanh, to ra nhng rung ng trong khng kh. Nhng rung ng ny c iu chnh bi s cng hng ca cc khoang yt hu, mi v ming to thnh dng m sc khc nhau ca ting ni. Ni cch khc: Tn s rung ca dy thanh m xc nh cao ca ting ni V tr/hnh dng ca mi, li v mi xc nh m sc. nn t phi xc nh m lng ca ting ni.Hnh di y minh ha tc khng kh xung quanh thanh mn v tn hiu ting ni xung quanh ming.

3. Nhn dng t ring l Trong ting Vit, ng ngha ca mt t ph thuc vo thanh iu. Khi thanh iu thay i, ngha ca t cng thay i theo. C 6 thanh iu trong ting Vit: khng du, huyn,sc, nng, hi, ng tng ng vi mi thanh iu, tn s c bn thay i theo mt quy lut ring.a. Khng duVi thanh iu khng du, tn s c bn khng thay i.

b.du huyn

Vi du huyn, tn s c bn gim dn.Nu gi F0 l tn s tng ng vi m khng du, s thay i tn s c bn ca du huyn c th c m t nh sau:F0, F0-10, F0-20, F0-30, F0-50, F0-60 c. Du sc

Vi du sc, tn s c bn tng dn.Nu gi F0 l tn s tng ng vi m khng du, th s thay i tn s c bn ca du sc c th c m t nh sau:F0-20, F0-20, F0-15, F0-10, F0-5, F0+5, F0+30, F0+70, F0+80d.Du nng

Nu gi F0 l tn s tng ng vi m khng du, th s thay i tn s c bn ca du nng c th c m t nh sau:F0, F0, F0-35, F0-50, F0-90, F0-120, F0-140

e.Du hiNu gi F0 l tn s tng ng vi m khng du, th s thay i tn s c bn ca du hi c th c m t nh sau:F0-30, F0-15, F0-20, F0-35, F0-55, F0-70, F0-75, F0-85, F0-90,F0-95, F0-90,F0-80, F0-90, F0-30

f. Du ng

Nu gi F0 l tn s tng ng vi m khng du, th s thay i tn s c bn ca du ng c th c m t nh sau :F0, F0-40, F0+20, F0+50, F0+60III. CC PHNG PHP NHN DNG V TNG HP TING NI 1. Cc m hnh Markov n 1.1 Chui Markov Trong ton hc, mt xch Markov hay chui Markov (thi gian ri rc), t theo tn nh ton hc ngi Nga Andrei Andreyevich Markov, l mt qu trnh ngu nhin thi gian ri rc vi tnh cht Markov. Trong mt qu trnh nh vy, qu kh khng lin quan n vic tin on tng lai m vic ch ph thuc theo kin thc v hin ti. Xch Markov l mt dy X1, X2, X3, ... gm cc bin ngu nhin. Tp tt c cc gi tr c th c ca cc bin ny c gi l khng gian trng thi S, gi tr ca Xn l trng thi ca qu trnh (h) ti thi im n. Nu vic xc nh (d on) phn b xc sut c iu kin ca Xn+1 khi cho bit cc trng thi qu kh l mt hm ch ph thuc Xn th: P(Xn+1 =x|X0 , X1, Xn)= P(Xn+1 =x|Xn)trong x l mt trng thi no ca qu trnh (x thuc khng gian trng thi S) . l thuc tnh Markov. Mt cch n gin hnh dung mt kiu chui Markov c th l qua mt opto hu hn (finite state machine). Nu h trng thi y ti thi im n th xc sut m h s chuyn ti trng thi x ti thi im n+1 khng ph thuc vo gi tr ca thi im n m ch ph thuc vo trng thi hin ti y. Do , ti thi im n bt k, mt xch Markov hu hn c th c biu din bng mt ma trn xc sut, trong phn t x, y c gi tr bng P(Xn+1 =x|Xn =y) v c lp vi ch s thi gian n (ngha l xc nh trng thi k tip, ta khng cn bit ang thi im no m ch cn bit trng thi thi im l g). Cc loi xch Markov hu hn ri rc ny cn c th c biu din bng th c hng, trong cc cung c gn nhn bng xc sut chuyn t trng thi ti nh (vertex) u sang trng thi ti nh cui ca cung . M hnh Markov n (ting Anh l Hidden Markov Model - HMM) l m hnh thng k trong h thng c m hnh ha c cho l mt qu trnh Markov vi cc tham s khng bit trc v nhim v l xc nh cc tham s n t cc tham s quan st c, da trn s tha nhn ny. Cc tham s ca m hnh c rt ra sau c th s dng thc hin cc phn tch k tip, v d cho cc ng dng nhn dng mu. Trong mt m hnh Markov in hnh, trng thi c quan st trc tip bi ngi quan st, v v vy cc xc sut chuyn tip trng thi l cc tham s duy nht. M hnh Markov nthm vo cc u ra: mi trng thi c xc sut phn b trn cc biu hin u ra c th. V vy, nhn vo dy ca cc biu hin c sinh ra bi HMM khng trc tip ch ra dy cc trng thi. Mt HMM c c trng bi nhng yu t sau:1) N, s lng ca cc trng thi trong m hnh.Mc d cc trng thi l n, i vi nhiu ng thc t thng l mt s ngha vt l thuc cc trng thi hoc b trng thi ca m hnh. Do , trong cc th nghim tung ng xu, mi trng thi tng ng vi mt ng xu thin lch khc bit. Trong m hnh chic bnh v qu bng, cc trng thi tng ng vi cc bnh. Ni chung cc trng thi ang kt ni vi nhau theo mt cch m bt k trng thi no c th t c t bt k trng thi khc (v d, mt m hnh ergodic), tuy nhin, chng ta s thy sau ny trong giy khc c th c mi lin kt ca cc trng thi thng quan tm. Chng ti biu th cc trng thi ring l l S = {S1, S2,. . ., Sn}, v trng thi ti thi im t l qt,

2) M, s lng cc biu tng quan st khc bit cho mi trng thi, tc l, kch thc bng ch ring bit.Cc biu tng quan st tng ng vi u ra vt l ca h thng ang c m hnh.i vi nhng th nghim nm ng xu nhng biu tng quan st c ch n gin l ng u hoc cui, bng v m hnh chic bnh chng c cc mu sc ca cc qu bng c la chn t bnh. Chng ti biu th cc biu tng ring l l V = {v1, v2,,vm}

3) xc sut chuyn i trng thi phn phi A = {a,} ni

i vi trng hp c bit ni m bt c nh nc c th t c bt k trng thi khc trong mt bc duy nht, chng ta c aij > 0 cho tt c i j. i vi cc loi khc ca HMMs, chng ta s c aij = 0 i vi mt hoc nhiu cp (i, j).

4) biu tng quan st xc sut phn phi trng thi j, B = {bj(k)},5) S phn b trng thi ban u = {i}

Vi gi tr thch hp ca N, M, A, B, v , HMM c th c s dng nh b sinh cung cp mt chui quan st(m mi quan st O, l mt trong cc biu tng t V, v T l s lng quan st theo th t) nh sau:(1) Chn mt trng thi ban u q1 = Si theo phn phi trng thi ban u T.2) t t = 1.3) Ot = vk theo phn b xc sut biu tng trong SI trng thi, tc l, bi (k).4) Chuyn trng thi mi qt+1 = Sj theo phn phi trng thi chuyn xc sut cho trng thi S, ngha l mt.5) t t = t + 1; tr li bc 3) nu t