1

LI CM N

Em xin chn thnh cm n Thy gio, Thc s V Vn Tng Cng tc

ti Cc k thut nghip v I, B cng an, ngi trc tip hng dn tn

tnh ch bo em trong sut qu trnh lm tt nghip.

Em xin chn thnh cm n tt c cc thy c gio trong khoa Cng ngh

thng tin - Trng HDL Hi Phng, nhng ngi nhit tnh ging dy v

truyn t nhng kin thc cn thit trong sut thi gian em hc tp ti

trng, em hon thnh tt ti ny.

Em cng xin chn thnh cm n Ban lnh o, tt c cc c ch, cc anh

ch ti Cng ty C phn Thit b Bu in, gip v to mi iu kin tt

cho em trong thi gian thc tp v lm tt nghip ti Trung tm.

Trong qu trnh lm tt nghip tuy c nhiu c gng nhng khng th

trnh khi nhng thiu st, em rt mong nhn c s gp qu bu ca tt

c cc thy c gio, ca hi ng phn bin v ca tt c cc bn.

Em xin chn thnh cm n!

Hi Phng, ngy ..........thng 7 nm 2009

Sinh vin

Trng Ngc Sn.

2

MC LC

LI CM N ................................................................................................... 1

MC LC ......................................................................................................... 2

M U .......................................................................................................... 4

CHNG 1: TN HIU - C S X L TN HIU ............................... 5

1.1. Tn hiu ................................................................................................ 5

1.2. Cc tn hiu ri rc theo thi gian ....................................................... 7

1.2.1 Cc phng php biu din tn hiu ri rc ................................. 7

1.2.2 Mt vi tn hiu ri rc c bn ..................................................... 8

1.2.3 Phn loi cc tn hiu ri rc ........................................................ 9

1.2.4 Cc thao tc x l n gin trn tn hiu ri rc theo thi gian. 13

1.2.5 Biu din h thng ri rc theo thi gian bng s khi ....... 14

1.2.6 Phn loi cc h thng ri rc theo thi gian ............................. 16

CHNG 2: C TRNG TING VIT ............................................... 18

2.1. c im ca Ting Vit ................................................................... 18

2.2. c im ng m ............................................................................... 18

2.3. c im t vng .............................................................................. 18

2.4. c im ng php ............................................................................ 19

2.5. m tit trong ting Vit ..................................................................... 20

CHNG 3: BI TON NHN DNG TING NI ............................ 23

3.1. Mt s khi nim c bn v m thanh v ting ni. ......................... 25

3.1.1 m thanh .................................................................................... 25

3.1.2 Cc c trng ca Ting ni ....................................................... 27

3.2. Mt s phng php nhn dng ting ni ......................................... 29

3.2.1 Mt s khuynh hng nghin cu nhn dng ting ni ............. 29

3.2.2 Cc n v x l ting ni .......................................................... 33

3.2.3 Mt s k thut kh nhiu .......................................................... 35

3.2.4 Mt s phng php nhn dng ting ni .................................. 36

CHNG 4: CHNG TRNH DEMO ................................................. 44

4.1. Thit k cc chc nng chnh ............................................................ 44

3

4.2. La chn ngn ng lp trnh ............................................................. 45

4.3. Xy dng b mu nhn dng ............................................................. 45

4.4. Mt s hnh nh ca chng trnh ..................................................... 46

NH GI KT QU V KT LUN ....................................................... 49

TI LIU THAM KHO ............................................................................... 50

4

M U

Ngy nay, cng vi s pht trin nhanh chng ca cng ngh thng tin,

trong c cng ngh x l m thanh. c bit trong lnh vc x l m thanh

trong nhn dng ting Vit c mt ngha quan trng mang li nhiu ng

dng thit thc cho x hi, mang li nhng thay i mang tnh cch mng

trong nhiu lnh vc, pht thanh, truyn hnh, vin thng... Trong vi thp k

gn y, nhn dng l mt vn cun ht nhiu nh khoa hc cc lnh vc

khc nhau : Ton hc, iu khin, in t, sinh hc ... Trc s pht trin

mnh m ca cng ngh thng tin, vn nhn dng cng c quan tm

nhiu hn nhm nng cao hiu qu giao tip ngi - my.

Trn th gii, cc ngn ng ph bin nh Anh, Php... c nhiu

phn mm nhn dng rt hiu qu. Vit Nam c nhiu cng trnh nghin

cu v lnh vc nhn dng ting ni (Speech recognition) trn c s l thuyt

cc h thng thng minh nhn to, nhiu kt qu tr thnh sn phm

thng mi nh ViaVoice, Dragon..., cc h thng bo mt thng qua nhn

dng ting ni cc h quay s in thoi bng ging ni... Trin khai nhng

cng trnh nghin cu v a vo thc t ng dng vn ny l mt vic

lm ht sc c ngha c bit trong giai on cng nghip ho hin i ho

hin nay ca nc ta.

Mc ch ca ti l nghin cu xy dng mt chng trnh nhn

dng ting ni ting Vit trong mi trng c nhiu vi u vo l tp t hn

ch l ting vit sau so snh vi cc mu c sn a ra kt qu. Ngoi

phn m u v kt lun n gm 4 chng:

Chng 1 : Tn hiu C s x l Tn hiu

Chng 2 : c trng Ting Vit

Chng 3 : Bi ton nhn dng Ting ni

Chng 4: Chng trnh Demo

5

CHNG 1: TN HIU - C S X L TN HIU

C s ca x l tn hiu chnh l bc u ca qu trnh nhn dng

ting ni, khi bn ni mt t my s thu ging ca bn, ting ni s c biu

din di dng tn hiu, qua qu trnh x l tn hiu, ting ni u vo s

c i chiu vi tp mu m my c hc sn a ra kt qu. Di

y chnh l mt s cch nhn tng quan v tn hiu.

1.1. Tn hiu

Tn hiu v mt ton hc l hm biu din trng thi vt l ca thng

tin. Ni chung, tn hiu l mt hm phc tp ca nhiu thng s. n gin

chng ta coi tn hiu l hm ca bin thi gian - tn hiu c 3 dng c bn:

- Tn hiu lin tc (tng t).

- Tn hiu ri rc (ly mu).

- Tn hiu s.

Ba loi tn hiu ny c mt cc v tr ca s hnh 1.1

Tn hiu lin tc l tn hiu c biu din bng hm s c bin s thi

gian c lp (hnh 1.2a).

Tn hiu ri rc (cn gi l tn hiu trch mu) l dy gi tr tn hiu

lin tc tng thi im ri rc v tn hiu c biu din di dng mt

dy s (hnh 1.2b). Tn hiu ri rc gp u ra mch lng t theo thi gian

(mch trchmu).

6

Tn hiu ri rc lng t theo bin l tn hiu c lng t theo

bin , thc cht l dy gi tr mu c quy trn theo cc mc lng t

bin (hnh 1.2c). Tn hiu ny gp u ra b lng t bin .

Tn hiu s l tn hiu lng t theo bin v m ho (hnh 1.2d). Cc

dng tn hiu va nu trn c m t trn hnh 1.2.

a. Tn hiu tng t.

b. Tn hiu ri rc (ly mu).

c. Tn hiu ri rc lng t theo bin ( lng t ho).

d. Tn hiu s ( gn cc bt c 2 cho cc mu lm trn).

Cc kiu tn hiu ny c biu din trong hnh 1. 2

Hnh 1.2. m t cc dng tn hiu

7

1.2. Cc tn hiu ri rc theo thi gian

1.2.1 Cc phng php biu din tn hiu ri rc

Nh ta bit, tn hiu ri rc theo thi gian x(n) thc cht l hm ca

bin c lp c kiu s nguyn. tn hiu x(n) ch c nh ngha i vi cc

gi tr nguyn ca n. Trong khi nghin cu, chng ta gi s rng tn hiu ri

rc theo thi gian c nh ngha i vi gi tr nguyn ca n thuc khong -

< n < . Theo qui c xem x(n) nh l mu th n ca tn hiu, Nu cho

rng x(n) l tn hiu nhn c do qu trnh ly mu ca tn hiu tng t

xa(t) th x(n) x(nT), trong T l chu k ly mu (thi gian gia hai ln ly

mu lin tip nhau)

Trong ti liu khi vit x(n) nh l cch vit n gin ca x(nT) hoc s

hiu l T=1.

Hnh 1.3. Biu din th ca tn hiu ri rc theo thi gian.

Ngoi phng php s dng th nh m t trn, cn c mt s

phng php khc tng i thun tin c s dng biu din tn hiu

(hoc dy) ri rc theo thi gian.

a. Biu din bng hm

V d: x(n) =

,0

,4

,1

x(n)

2

1.5 1.7

0.9 1.0 1.2

0.7 0.7

- 4 .

-4 -2 -1 0 1 2 3 5 n

-0.8 -0.8

vi n = 1,3

vi n = 2

vi cc gi tr cn li

8

b. Biu din bng bng

V d:

n -2` -1 0 1 2 3 4 5

x(n .... 0 0 0 1 4 1 0 0

c. Biu din qua dy s

Tn hiu hoc dy v tn c m t qua v d di y.

x(n) = {0,0 1,4,1,0,0}

trong k hiu dng ch thi im gc (n = 0).

Dy x(n) c gi tr bng 0 vi n < 0 c biu din bng cch sau:

x(n) = {0,1,4,1,0,0}

y thi im gc vi dy x(n) c gi tr bng 0 nu n

9

1.4 Biu din th ca tn hiu mu n v

b. Dy nhy bc n v

Dy ny cn c gi l tn hiu nhy bc n v hay hm bc thang v

c nh ngha qua hm sau:

,0

,1)(nu

Gia tn hiu nhy bc n v v tn hiu xung n v c mi quan h:

u(n) = 0

)(k

kn v )1()()( nunun

Tn hiu nhy bc n v c m t trn hnh sau:

1.5 Biu din bng th ca tn hiu nhy bc n v

1.2.3 Phn loi cc tn hiu ri rc

Cc phng php ton hc c dng trong vic phn tch tn hiu v

h thng ri rc theo thi gian hon ton ph thuc vo c th ca tn hiu.

)(n

1

-2 -1 0 1 2 3 4

n

n>0

n

10

a. Tn hiu nng lng v tn hiu cng sut

Nng lng E ca tn hiu x(n) c nh ngha bng cng thc:

E n

nx2

)( ,

y )(nx l modul ca tn hiu. Vi cch nh ngha ny th cng

thc trn c th c s dng tnh nng lng ca tn hiu phc cng nh

ca tn hiu thc.

Nng lng ca tn hiu c th l hu hn hoc v hn. Nu E l hu

hn (0 < E < ) th x(n) c gi l tn hiu nng lng. phn bit nng

lng ca tn hiu ri rc, thng thng ngi ta s dng thm ch s x i

vi E v bit l Ex.

Rt nhiu tn hiu vi nng lng v hn li c cng sut hu hn.

Cng sut trung bnh ca tn hiu ri rc theo thi gian x(n) c nh ngha

bng biu thc:

P= n

LimN

Nn

nxN

2)(12

1

Nu nh ngha nng lng tn hiu ca dy x(n) trong khong hu hn

-N < n < N l:

EN N

Nn

nx2

)(

th c th xc nh nng lng tn hiu E qua biu thc

E N

Lim EN

v cng sut trung bnh ca tn hiu x(n):

P N

Lim NEN 12

1

R rng rng nu E l hu hn th P=0. Trong khi nu E l v hn

th cng sut trung bnh P c th l hu hn hoc v hn. Nu P l hu hn

(v khc 0) tn hiu s c gi l tn hiu cng sut.

11

b. Tn hiu tun hon v khng tun hon

Nh nh ngha trong phn 1.3 tn hiu x(n) c gi l tun hon

vi chu k N(N>0) khi v ch khi:

x(n + N) = x(n) vi mi n

Gi tr nh nht ca N tho mn biu thc trn c gi l chu k c

bn. Nu khng c bt c mt gi tr no ca N bt trn l ng th tn hiu

c gi l khng tun hon. Hnh di l mt v d v tn hiu tun hon.

M t bng th tn hiu tun hon

Khi kho st tn hiu hnh sin ta nhn thy rng tn hiu.

x(n) = Asin2 f0n

l tn hiu tun hon nu f0 l mt s hu t, hay ni cch khc f0 c th

c biu din qua biu thc:

N

kf0

trong k v N l nhng s nguyn.

Nng lng ca tn hiu tun hon x(n) trong mt chu k hay trong mt

khong 0 n N-1 l hu hn nu x(n) nhn cc gi tr hu hn trong mt

chu k. Tuy vy, nng lng ca tn hiu tun hon vi - n l v hn.

Mt khc, cng sut trung bnh ca tn hiu tun hon l hu hn v bng

cng sut trung bnh trong mt chu k. Nh vy, nu x(n) l tn hiu tun

hon vi tn s c bn N v c cc gi tr hu hn th cng sut ca n c

xc nh qua biu thc:

x(n)

1

-1 0 1 2 3 4 n

12

1

0

2)(

1 N

n

nxN

P

Suy ra rng tn hiu tun hon l tn hiu cng sut.

c. Tn hiu i xng (chn) v tn hiu khng i xng (l)

Tn hiu c gi tr thc x(n) c gi l i xng (chn) nu:

x(-n) = x(n)

v c gi l phn i xng (l) nu:

x(-n) = - x(n)

C th nhn thy rng nu x(n) l l th x(0) =0

Tn hiu chn c th c biu din qua cng thc:

)]()([2

1)( nxnxnxe

Tn hiu l c th c biu din qua cng thc

)]()([2

1)(0 nxnxnx

)(nx

1

-4 -3 -2 -1 0 1 2 3 4

n a

)(nx

1

0 1 2 3 4

n

-5 -4 -3 -2 -1 5

13

Nh vy nu x(n) l tn hiu bt k th ta c th biu din x(n) di

dng sau:

)]()()()([2

1)( nxnxnxnxnx

)()([2

1)]()([

2

1nxnxnxnx

= x )()( nxone

Nh vy mt tn hiu bt k c th c biu din di dng tng ca

tn hiu chn v tn hiu l

1.2.4 Cc thao tc x l n gin trn tn hiu ri rc theo thi gian.

Trong phn ny ta s xem xt mt vi x l n gin lin quan n cc

bin c lp v bin ca tn hiu.

a.Php dch cc bin c lp.

Tn hiu x(n) c th c dch chuyn theo thi gian bng cch thay th

bin c lp n bi n- k trong k l s nguyn. Nu k l s nguyn dng th

kt qu ca s dch chuyn v thi gian s l s tr ca tn hiu vi k n v

ca thi gian. Nu k l s m th kt qu ca s dch chuyn theo thi gian l

s vt trc ca tn hiu vi k n v thi gian.

b. Php nhn, cng v php ly t l.

Vic thay i ca bin tn hiu ri rc theo thi gian c th c

thc hin qua cc php ton (thao tc) cng, nhn, ly t l.

Ly t l cn c gi l php nhn ca dy vi hng s v thc hin

bng cch nhn gi tr ca mi mu vi chnh hng s . Gi s rng s

c k hiu l A, khi ta c th vit:

y(n) = Ax(n), - n

Tng ca hai tn hiu x1(n) v x2(n) l mt tn hiu y(n) vi gi tr

mi thi im bng tng cc gi tr x1(n) v x2(n) tng ng thi im

v nh vy:

y(n) = x1(n) + x2(n), - n

14

Tch ca hai tn hiu l mt tn hiu khc vi gi tr mi thi im

bng tch cc gi tr ca hai tn hiu thi im tng ng, hay:

y(n) = x1(n).x2(n), - n

1.2.5 Biu din h thng ri rc theo thi gian bng s khi

a. B nhn vi hng s (constant muLTIplier)

Php ton ny c m t trn hnh di v biu din mt php ly t

l ca tn hiu u vo x(n).

Biu din s ca h nhn vi hng s.

b. B cng (Adder)

Hnh di m t mt h thng (b cng) thc hin cng hai dy tn

hiu vi kt qu l mt dy khc - dy y(n) (dy tng).

Trong qu trnh thc hin thao tc cng ta khng cn phi lu tr bt

c mt gi tr trung gian no bi v php cng c thc hin tc th khng

nh.

x(n) a y(n) = ax(n)

x2(n)

x1(n)

y(n)=x1(n) + x2(n)

+

Biu din qua s ca b cng.

15

c. B nhn tn hiu (signal muLTIplier)

biu din mt b nhn ca hai dy tn hiu vi kt qu l mt dy tch

y(n). Cng ging nh hai trng hp trc, y php nhn cng l php

ton khng nh.

Biu din qua s ca h nhn.

d. Phn t tr n v

Phn t tr n v (unit delay element) l h thng c bit c tc dng

lm tr tn hiu i qua vi thi gian bng mt n v. h thng ny l h thng

c nh

Trong min Z, phn t ny c k hiu bi z-1. s biu din

e. Phn t vt trc n v (Unit advance element)

Tri ngc vi h tr n v, h vt trc n v s chuyn u vo

x(n) dch v trc mt mu theo thi gian c th nhn c u ra tn

hiu y(n) = x(n+1).

Biu din qua s ca phn t vt trc.

x2(n)

x1(n) y(n)=x1(n)x2(n)

x

Z-1 x(n) y(n) = x(n-1)

z x(n) y(n) = x(n+1)

16

1.2.6 Phn loi cc h thng ri rc theo thi gian

a. H nh v khng nh

H thng ri rc theo thi gian c gi l khng nh (memoryless)

hoc tnh (static) nu tn hiu ra ca n mi thi im ch ph thuc vo tn

hiu u vo cng mt thi im m khng ph thuc vo cc gi tr mu

ca tn hiu u vo trong qu kh hoc trong tng lai. Trong trng hp

ngc li, h thng c gi l c nh hoc bin i (dynamic). Nu u ra

ca h thng thi im n c th c xc nh mt cch hon ton bi cc

mu u vo trong khong t n-N n n (N 0) th h thng c gi l c

nh trong khong N. Nu N = 0 th h s l h khng nh. Nu 0 < N < h

thng c gi l h nh hu hn, ngc li nu N = th h c gi l h

nh v hn.

b. H thng bt bin v khng bt bin theo thi gian

Mt h c gi l bt bin theo thi gian nu nh c trng vo/ra ca

n khng thay i theo thi gian

nh l. Mt h thng relaxed c gi l bt bin theo thi gian khi

v ch khi:

x(n) y(n)

suy ra x(n-k) y(n-k)

i vi mi tn hiu u vo x(n) v mi thi gian dch chuyn k.

c. H tuyn tnh v khng tuyn tnh

Cc h thng c th c chia lm hai loi tuyn tnh v khng tuyn

tnh. H thng c gi l tuyn tnh nu n tha mn nguyn l xp chng

nh l : H thng c xem l tuyn tnh khi v ch khi:

T[a1x1(n) + a2x2(n)] = a1 T[x1(n)] + a2T[x2(n)]

i vi mi dy tn hiu u vo x1(n), x2(n) v cc hng s a1, a2

T

T

17

x1(n)

+

x2(n)

y(n)

a1

a2

T

T

T

x1(n)

+ y(n)

a1

a2 x2(n)

Biu din ho ca nguyn tc xp chng

18

CHNG 2: C TRNG TING VIT

2.1. c im ca Ting Vit

Ting ni thng xut hin di nhiu hnh thc m ta gi l m

thoi , vic m thoi th hin kinh nghim ca con ngi.Nhng ngi c

iu kin th cht v tnh thn bnh thng th rt d din t ting ni ca

mnh do ting ni l phng tin giao tip chnh trong lc m thoi.

Ting ni l m thanh mang mc ch din t thng tin,l cng c t

duy v tr tu,ting ni mang tnh c trng ca loi ngi.

Ting Vit thuc ngn ng n lp, tc l mi mt ting (m tit) c

pht m tch ri nhau v c th hin bng mt ch vit. c im ny th

hin r rt tt c cc mt ng m, t vng, ng php.

2.2. c im ng m

Trong ting Vit c mt loi n v c bit gi l ting. V mt ng

m, mt ting l mt m tit. H thng m v ting Vit phong ph v c tnh

cn i, to ra tim nng ca ng m ting Vit trong vic th hin cc n v

c ngha. Nhiu t tng hnh, tng thanh c gi tr gi t c sc. Khi to

cu, to li, ngi Vit rt ch n s hi ho v ng m, n ng iu ca

cu vn.

2.3. c im t vng

Mi ting, ni chung, l mt yu t c ngha. Ting l n v c s ca

h thng cc n v c ngha ca ting Vit. T ting, ngi ta to ra cc n

v t vng khc nh dng s vt, hin tng..., ch yu nh phng thc

ghp v phng thc ly.

Vic to ra cc n v t vng phng thc ghp lun chu s chi

phi ca quy lut kt hp ng ngha. Theo phng thc ny, ting Vit trit

s dng cc yu t cu to t thun Vit hay vay mn t cc ngn ng

khc to ra cc t, ng mi, v d: tip th, karaoke, th in t (e-mail),

19

th thoi (voice mail), phin bn (version), xa l thng tin, lin kt siu vn

bn, truy cp ngu

Vic to ra cc n v t vng phng thc ly th quy lut phi hp

ng m chi phi ch yu vic to ra cc n v t vng v d chm cha,

chng ch, ng ng nh, th thn, lng la lng ling, v.v.

2.4. c im ng php

T ca ting Vit khng bin i hnh thi. c im ny s chi phi

cc c im ng php khc. Khi t kt hp t s tr thnh cc kt cu nh

ng, cu. Trong ting Vit khi ni Anh ta li n l khc vi Li n anh

ta, Nh trt t kt hp ca t m c ci khc vi ci c, tnh cm

khc vi cm tnh. Trt t ch ng ng trc, v ng ng sau l trt t

ph bin ca kt cu cu ting Vit

Ting Vit rt coi trng phng thc trt t t v h t ngoi ra trong

ting Vit cn dng phng thc l ng iu.

Phng thc h t cng l phng thc ng php ch yu ca ting

Vit. Nh h t m t hp anh ca em khc vi t hp anh v em, anh

v em. H t cng vi trt t t cho php ting Vit to ra nhiu cu cng c

ni dung thng bo c bn nh nhau nhng khc nhau v sc thi biu cm.

V d, so snh cc cu sau y:

- ng y khng ht thuc

- Thuc, ng y khng ht

Ng iu gi vai tr trong vic biu hin quan h c php ca cc yu

t trong cu, nh nhm a ra ni dung mun thng bo. Trn vn bn,

ng iu thng c biu hin bng du cu. Chng ta th so snh hai cu

sau thy s khc nhau trong ni dung thng bo:

- m hm qua, cu gy.

- m hm, qua cu gy.

Qua mt s c im ni bt va nu trn y, chng ta c th hnh

dung c phn no bn sc v tim nng ca ting Vit.

20

2.5. m tit trong ting Vit

m tit l m v nh nht khi ni. D pht m c tht chm,tht tch

bch th nhng m thanh ca pht ngn cng khng th chia nh c na.

Mi m tit ting Vit l mt khi hon chnh trong pht m, nhng khng

phi l mt khi bt bin m c cu to lp ghp. Khi lp ghp y c th

tho ri tng b phn ca m tit ny hon v vi b phn tng ng ca

cc m tit khc.

V d:

tin u u tin o tt t m tit v hon v thanh iu

hin i hi in hon v phn sau in cho ai

nh ay nhy i thanh iu gi nguyn v tr cng vi phn u nh

v

m tit v th c tnh ton vn c pht m bng mt t cng ca b

my pht m.Cc t cng ca c ni tip nhau lm thnh mt chui m tit

v c th hnh dung bng mt chui ng cong hnh sin .

Trong s trn l hai cch pht m c v qu.Trong pht m

th nht c 2 m tit,m [u] nm nh m tit u.Trong pht m th hai c

mt m tit v m [u] nm sn ca m tit.

Cu trc tng qut ca mt m tit trong ting Vit l

21

Cn y l cu trc cht ch ca mt m tit trong ting Vit

C th hnh dung v cu to m tit ting vit trong mt m hnh nh

sau:

Thanh iu: khng (zero), huyn (`), hi (?), ng ( ) Sc ( ' ), nng (.)

t

m u

Vn

o a n

m m m chnh m cui

m u: thng l ph m, c gi l ph m u,n c chc nng

to ra m sc cho m tit lc m u.m u c th vng mt trong mt s

trng hp nh khi ta ni an,m

m m: m m l yu t ng v tr th hai, sau m u. N to

nn s i lp trn mi (voan) v khng trn mi (van), c chc nng lm

thay i m sc ca m tit lc khi u v lm khu bit m tit ny vi m

tit khc.v d nh tn v ton.m m c th vng mt trong mt s

trng hp khi c m u v o.

m chnh : m chnh ng v tr th ba trong m tit, l ht nhn, l

nh ca m tit, n mang m sc ch yu ca m tit. m chnh lun lun c

mt trong mi m tit c chc nng quy nh m sc ch yu ca m tit .m

chnh lun lun l nguyn m.

m cui : c th l ph m hoc l bn nguyn m (ting vit c 2 bn

nguyn m l i v u). m cui c v tr cui cng ca m tit v c chc nng

kt thc m tit,do vy khi c am cui th m tit ko c kh nng kt hp vi

m khc,vd nh cimt s m cui vn c kh nng kt hp vi m khc

22

nh quc th thnh qut hay qunh th y vn c coi l m cui v

sau l c mt ca mt m cui gi l m cui zezo.

Thanh iu : lun c mt trong m tit v c ngha quyt nh m tit

v cao. Ting Vit c 6 thanh iu: thanh ngang (khng du, ting Anh:

zero /level), huyn (falling), ng (broken), hi (curve), sc (rising), nng

(drop).C nhiu kin khc nhau v v tr ca thanh iu trong m tit.

Nhng kin cho rng thanh iu nm trong c qu trnh pht m ca m tit

(nm trn ton b m tit) l ng tin cy nht v v tr ca thanh iu.

23

CHNG 3: BI TON NHN DNG TING NI

Khi qut v nhn dng

Hin nay cha c mt nh ngha chung no v nhn dng, nhng v

bn cht ca qu trnh nhn dng mt i tng cha bit no l sp xp

a i tng cha bit v lp cc i tng bit. Thc hin vic so snh

a ra kt lun i tng cn nhn dng thuc lp i tng no bit.

Nhng yu t cn quan tm trong bi ton nhn dng

Khng gian biu din quan st: L tp hp cc k hiu, s liu miu t

i tng sau qu trnh cm nhn.

Khng gian c tnh: l tp hp cc miu t c tnh sau qu trnh trch

chn c tnh.

Khng gian din dch: l tp hp cc tn ca cc i tng hoc tn ca

cc lp i tng cho bit i tng quan st thuc v lp no.

Cc vn ca h thng nhn dng

Biu din hoc miu t i tng nhn dng

Trch chn c tnh: Qu trnh trch chn c tnh, cc c trng c bn

phi m bo cc tiu ch sau:

. Gim c th nguyn khng gian biu din

. m bo c lng thng tin phn bit i tng ny

vi i tng khc

.C ng cc c tnh chnh

Qu trnh hc: qu trnh hc thc cht l qu trnh nhm cc lp c

cng mt s c tnh chnh, c mt s phng php hc sau:

. Hc c mu: l s hc c bt u bi tn ti s phn lp

i vi mt s i tng mu hoc bit c tnh ca cc lp i tng, ni

cch khc l xc nh c bin gii gia cc lp sao cho c th nhn

bit c i tng thuc lp no.

. Hc khng c mu: qu trnh hc khng c mu bt u khi s

phn lp cha hnh thnh, v khng c mu. Qu trnh hc nhm tin hnh

24

nhm dn dn trn c s cc i tng quan st c tng t gn nhau

tin hnh s phn lp.

Qu trnh ra quyt nh : Qu trnh ra quyt nh l tm ra 1 lut da

trn c s bit s phn lp cc i tng cng nh c trng ca cc lp

quyt nh mt i tng quan st thuc 1 lp no hoc ng nht vi mt

phn t no .

Khi qut v nhn dng ting ni

Nhn dng ting ni l mt qu trnh nhn dng mu, vi mc ch l

phn lp (classify) thng tin u vo l tn hiu ting ni thnh mt dy tun

t cc mu c hc trc v lu tr trong b nh. Cc mu l cc n

v nhn dng, chng c th l cc t, hoc cc m v.

Nhn dng ting ni l mt k thut c th ng dng trong rt nhiu

lnh vc ca cuc sng : trong vic iu khin (iu khin robot, ng c,

iu khin xe ln cho ngi tn tt), an ninh quc phng

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.

Ngi ta chia cc dng bi ton nhn dng ting ni theo mt s tiu

ch sau:

- Nhn dng ting ni ph thuc ngi ni/ c lp ngi ni

25

- Kiu li ni: lin tc hay ri rc

- Kch thc t in: nh, trung bnh hoc ln

- Nhn dng trong mi trng c nhiu hay khng c nhiu

Da vo kch thc t in, cc h thng nhn dng ting ni cn c

chia thnh 3 loi chnh sau :

- Cc h thng t in nh: thng t 20- 200 t.

- Cc h thng t in trung bnh: thng t 201- 1000 t.

- Cc h thng t in c ln: c t trn 1000 t.

3.1. Mt s khi nim c bn v m thanh v ting ni.

3.1.1 m thanh

+ sng m v cm gic m

- Khi mt vt giao ng v mt pha no , lp khng kh lin trc

n b nn li v lp khng kh lin sau n b dn ra. S dn v nn ca cc lp

khng kh lp i lp li to ra trong khng kh mt sng dc n hi vi tn

s no . Sng khng kh truyn ti tai ngi lm cho mng nh dao ng

theo tn s , khi tn s sng t n mt mc nht nh th to ra cm

gic m thanh trong tai ngi

- Mng nh tai ngi ni chung thu c sng c tn s t 16hz n

20.000hz. Trong khong tn s dao ng c gi l dao ng m thanh

hay m thanh.

+ cao ca m

- Nhng m thanh c tn s khc nhau gy cho ta nhng cm gic m

khc nhau, m c tn s ln gi l m cao cn m c tn s nh gi l m

thp hay m trm.

+ Nng lng ca m

- Cng nh cc sng c hc khc, sng m mang nng lng t l vi

bnh phng bin sng. Nng lng s truyn t ngun m ti tai

ngi.

26

+ Cng m

- L nng lng c sng m truyn trong mt n v thi gian qua

mt n v din tch t vung gc vi phng truyn (w/m2). i vi tai

ngi, cng m (I) l tham s khng quan trng bng gi tr t s I/I0 vi

(I0 l cng chun). Ngi ta nh ngha n ca m thanh L qua biu

thc sau:

L=lg(I/I0)

Th nguyn ca L l Ben (k hiu: B). Nh vy khi L=1,2,3 c ngha

l cng m I ln hn 10, 102, 103ln cng m chun I0

Sau y l mt s mc m lng

- Ting n trong phng: khong 30 dB

- Ting n o ngoi ng ph: khong 90 dB

- Ngng au tai: khong 130 dB

+ to ca m

to ca m (m lng) i vi tai ngi khng trng vi cng

m. Tai ngi nghe thnh nht i vi cc m trong min tn s 1000-5000Hz

v nghe m cao thnh hn m trm.

+ m sc

m sc l mt c tnh sinh l ca m, c hnh thnh trn c s cc

c tnh vt l ca m l tn s v bin . Thc nghim chng t rng khi

mt dao ng m thanh pht ra mt m c tn s f0 th ng thi cng pht ra

cc m c tn s f1=2f0, f3=3f0

m c tn s f0 gi l m c bn hay ho m th nht, cc m c tn s

cao hn gi l ho m th 2, th 3,m c bn bao gi cng mnh nht, cc

ho m c tc dng quyt nh m sc ca m c bn. Tu theo cu trc

khoang ming, c hng v khoang mi ca tng ngi m c cc ho m

khc nhau.

27

3.1.2 Cc c trng ca Ting ni

Nng lng v ln trung bnh thi gian ngn

Nng lng thi gian ngn c nh ngha theo cng thc sau:

m

mnwmxE 2)]()([ (3.1.1)

Do tnh nng lng c php tnh bnh phng nn kt qu thng c

gi tr rt ln. Ngi ta thay th bng mt i lng khc l ln trung bnh.

m

n mnwmxM )(|)(| (3.1.2)

Trong w(n-m) l khung ca s ly tn hiu m thanh.

Cn c vo cc gi tr nng lng hoc ln thi gian ngn c th

phn bit c cc on hu thanh v thanh hoc cc on tn hiu nhiu

nn.

Tn s ct khng trung bnh thi gian ngn

Cc tn hiu ri rc theo thi gian, khi nim tn s ct khng c ngha

l s ln tn hiu i du. y l mt i lng tn s n gin ca tn hiu.

V d tn hiu hnh sin c tn s F0 , tn s ly mu Fs c Fs/F0 mu trong mt

chu k sng sin, trong khi mi chu k c hai ln ct khng, do tn s

ct khng trung bnh thi gian di l Z = 2F0/Fs s ln ct trn mu. Nh vy

tn s ct khng trung bnh cng l mt cch xc nh tn s ca sng hnh

sin. Tn hiu ting ni l tn hiu bng rng nn thng xc nh tn s ct

khng trong on thi gian ngn, cng thc chung nh sau:

m

n nmwmxmx )(|)]1(sgn[)](sgn[|Z (3.1.3)

Trong :

sgn[x(n)] = 1 khi x(n) 0

= -1 khi x(n) < 0

w(n) : ca s ly tn hiu

w(n) = 1 nu 0 n N-1= 0 trng hp cn li.

28

Nng lng, ln v tn s ct khng thi gian ngn l cch n gin

v hiu qu xc nh phn nhiu nn v tn hiu, phn tn hiu v thanh v

hu thanh. Bng thc nghim quan st trc quan ta thy : Phn c tn hiu m

thanh th bin sng m ln hn phn nhiu nn. Mt khc gi tr trung bnh

bin sng m ca hai on m thanh c tn hiu v nhiu nn u xp x

khng.

Khi cn phn bit phn nhiu nn v tn hiu, phn tn hiu v thanh v

hu thanh, thng ta ch cn mt ch tiu trn cng phn bit. Nhng

i khi trng hp phc tp hn trong phn bit m xt v nhiu nn ta cn

phi s dng n c hai ch tiu nng lng v tn s ct khng. Ngoi ra cc

ch tiu trn cn c s dng thit lp chu k Pitch(tn s c bn ca

ting ni).

Hm sai khc ln trung bnh thi gian ngn

Di y s trnh by mt phng php rt hu dng trch ra c

tn s Pitch(tn s c bn ca ting ni). Hm sai khc ln trung bnh thi

gian ngn c nh ngha nh sau :

Nko

koi

Pii yyN

PAMDF1

||1

)( (3.1.4)

Gi s chui {yn} tun hon vi chu k P0 th hm AMDF s t gi

tr cc tiu ti P0 . Nh vy vic xc nh chu k Pitch ca ting ni s thng

qua xc nh ch s P0 m ti hm AMDF i gi tr cc tiu. Trong thc

t chu k Pitch ting ni ca mt ngi nm trong mt min gii hn, v vy

khng cn thit phi tnh ton cho mi gi tr P ca hm AMDF. Qua thc

nghim m thanh ting ni con ngi, chu k Pitch nm trong khong 2.5

mili giy n 19.5 mili giy. Vi tc ly mu thc hin trong n l

11025 mu trn giy th chu k Pitch nm trong khong 30 n 220.

29

3.2. Mt s phng php nhn dng ting ni

3.2.1 Mt s khuynh hng nghin cu nhn dng ting ni

Hin nay trn th gii c 4 khuynh hng nghin cu nhn dng ting

ni, gm :

- Hng tip cn m hc ng m hc.

- Hng tip cn nhn dng theo mu thng k.

- Hng tip cn tr tu nhn to.

- Hng tip cn s dng mng nron.

3.2.1.1 Hng tip cn m hc ng m hc nhn dng ting ni

Khuynh hng m hc ng m hc da trn l thuyt v ng m

hc. L thuyt ny cho rng tn ti cc n v ng m xc nh, c tnh phn

bit trong li ni v cc n v ng m c c trng bi mt tp cc c

tnh tn hiu ting ni . Mc d cc c tnh m hc ca cc n v ng m

bin thin rt ln theo c ging ngi ni ln tc ng ca cc n v ng m

xung quanh (cn gi l hin tng ng pht m), nhng vn tn ti cc qui

tc cho php gii quyt nhng vn nh vy

Bc u tin trong hng tip cn m hc ng m hc nhn dng

ting ni l phn on v gn nhn. Bc ny chia tn hiu ting ni thnh cc

on c cc c tnh m hc c trng cho mt (hoc vi) n v ng m

(hoc lp), ng thi gn cho mi on m thanh mt hay nhiu nhn ng

m ph hp.

Bc th hai xc nh mt t (hoc mt chui t) ng trong s chui

cc nhn ng m c to ra sau bc mt v phi tun th mt s iu kin

rng buc (tc l cc t c chn ra trong t in cho trc phi ph hp

nguyn tc ng php v c ngha)

S khi ca h thng nhn dng ting ni theo hng m hc ng

m hc th hin trn Hnh 1.1

30

H thng nhn dng ting ni theo khuynh hng ny gp phi kh

nhiu vn kh khn do n cha c p dng nhiu trong thc t.

Khuynh hng ny i hi s hiu bit su sc v cc tnh cht m hc ca

cc n v ng m. Ngun kin thc ny kh c th y c nn nhn

dng ting ni theo khuynh hng ny vn cn l ch nghin cu th v

nhng cn c nghin cu v tm hiu su sc hn c th p dng thnh

cng vo cc h thng nhn dng ting ni thc t.

3.2.1.2 Hng tip cn nhn dng theo mu thng k

Nhn dng ting ni theo khuynh hng ny l s dng trc tip cc

mu tn hiu ting ni m khng phi xc nh r rng cc c tnh m hc

(so vi khuynh hng m hc ng m hc) v khng phi phn on ting

ni. Cc h thng nhn dng ting ni theo khuynh hng ny c thc hin

theo hai bc:

Bc th nht: S dng tp mu ting ni (c s d liu ting ni)

hun luyn h thng, tri thc v ting ni ca h thng nhn dng ting ni

c tch lu thng qua qu trnh hun luyn

Bc th hai: Nhn dng, thc hin so snh ting ni cha bit vi cc

mu c hun luyn.

Nguyn tc c bn ca hng ny l nu c s d liu dng cho hun

luyn c cc phin bn ca mu cn nhn dng th qu trnh nhn dng c

31

th xc nh c cc c tnh m hc ca mu (mu c th l m v, t hoc

cm t).

Hng tip cn theo mu thng k c ccchc nng ch yu sau:

- Phn tch v xc nh cc tham s: Tn hiu ting ni c phn tch

thnh mt chui cc c trng xc nh cc mu nhn dng. i

vi tn hiu ting ni, cc c trng ny thng l kt qu ca mt

s k thut phn tch ph nh ngn hng b lc, phn tch m ho

d bo tuyn tnh (LPC), bin i Fourier ri rc (DFT)

- Hun luyn mu: Mt s mu tng ng vi cc n v m thanh

cng loi c s dng hc, trch chn ra cc c trng ca mu

.

- Khi phn lp mu: Mu u vo cha bit c so snh vi mu

i din ca mt loi m thanh no v o khong cch (cn gi l

ging nhau) gia mu u vo v mu chun.

- Khi nguyn tc chn: Cc ch s v im ging nhau gia cc mu

tn hiu ting ni u vo v mu chun c s dng quyt nh

mu chun no ph hp nht vi mu u vo cha bit.

Vic chn hng tip cn ny c nhng u v nhc im sau:

- Tnh n gin v d hiu trong vic p dng thut ton

- Tnh bt bin trong thut ton so snh mu v quyt nh i vi

mi t vng, mi ngi s dng

- S thc hin ca h thng rt nhy cm vi s lng d liu hun

luyn c th cung cp cho lp cc mu chun. Ni chung, hun

luyn cng nhiu th hiu sut thc hin ca h thng cng cao.

- Khng c kin thc ting ni c bit dng xc nh h thng

v vy phng php ny khng nhy cm vi vic chn t vng,

c php v ng ngha.

32

- S tnh ton cho hun luyn mu v phn lp mu ni chung l

tuyn tnh i vi s mu hun luyn hoc nhn dng, v vy khi

s lp ln th s php tnh tng ln cng nhanh.

- Tng i d rng buc trc tip cc thnh phn ng php (v c

ng ngha) vo cu trc nhn dng mu, do ci thin c tnh

chnh xc nhn dng v gim c s tnh ton

3.2.1.3 Hng tip cn tr tu nhn to cho nhn dng ting ni

Nhn dng ting ni theo hng tr tu nhn to l s kt hp gia

khuynh hng m hc vi khuynh hng nhn dng mu v n khai thc cc

tng ca hai khuynh hng . Nhn dng ting ni theo khuynh hng

ny l c gng t ng ho th tc nhn dng theo cch m con ngi p

dng tr tu ca mnh hnh dung, phn tch v cui cng a ra quyt nh

trn cc c trng m hc o c. Trong thc t, cc k thut nhn dng

ting ni theo khuynh hng ny l s s dng h chuyn gia cho s phn

on v gn nhn, nh th bc ct yu v kh khn nht ny c th c

thc hin khng ch nh cc thng tin m hc ( tng nhn dng theo

khuynh hng m hc) m cn phn bit cc mu m thanh ( tng ca

nhn dng mu).

tng c bn ca hng tip cn tr tu nhn to vo nhn dng ting

ni l thu thp kin thc t cc ngun tri thc khc nhau gii quyt cc vn

ang t ra, v d tip cn tr tu nhn to cho vic phn on v gn nhn

ting ni cn c s tng hp cc kin thc v m hc, kin thc t vng, kin

thc ng php, kin thc ng ngha v thm ch c kin thc thc t.

3.2.1.4 Hng tip cn s dng mng nron

Xt v kha cnh m phng tr tu con ngi th mng nron nhn to

c th coi l phng php tip cn tr tu nhn to, tuy nhin c th coi y l

mt phng php ring.

Phng php ny thc cht c c s l phng php nhn dng mu

thng k. Khc c bn l cch thc lu tr mu. Phng php ny ch lu tr

33

vect s liu th hin tham s c trng thng qua trng s lin kt v h s

hiu chnh.

3.2.2 Cc n v x l ting ni

3.2.2.1 Tn s ly mu

Qu trnh ly mu to ra tn hiu ri rc hoc tn hiu s t tn hiu

tng t. Tn s ly mu l s ln ly mu c tnh trong mt n v thi

gian, thng thng l giy. Tn s ly mu k hiu l Fs.

Khong thi gian m qu trnh ly mu c lp li gi l chu k ly

mu.

V d: Fs = 11025 Hz

1s thu c 11025 mu

1ms thu c 11025/1000 11 mu.

S bit lu mt mu c th l 8 hoc 16 bit.

+ 8 bit/1 mu: x(n) (0,28 - 1)

Ngng lng tuyt i l 128

+ 16 bit/1 mu: x(n) (2-15, 215-1)

Ngng lng tuyt i l 0

3.2.2.2 Tn s c bn

Mt m thanh c th l t hp ca nhiu tn s, tn s chnh bao trm

trong m c gi l tn s c bn. Trong ting ni, tn s c bn l p ng

ca s rung ng cc dy thanh m, tn s c bn thng c k hiu l F0.

Tn s c bn c gi tr ph thuc vo tn s ly mu v khong cch a,

l khong cch gia hai nh ca cc sng m tun hon.

n v ca tn s l Hertz, k hiu l Hz. Mi Hz bng 1 dao ng/1s.

v 1KHz s bng 1000 Hz.

3. 2. 2. 3 Nhiu

Nhiu i vi h thng l loi m thanh ngoi mong mun hoc khng

phi ting ni sinh ra trong mi trng xung quanh. Ngay c b pht m ca

con ngi i khi cng sinh ra nhiu, chng hn nh ting th, ting bt li,

34

ting chp ming c khi mi chm vo micro... Khng d g c th lc c

mi th nhiu, ta ch tm cch ti thiu ho chng c th nng cao cht

lng ca h thng nhn dng.

Vi tn hiu ting ni l sn, tn hiu nhn c sau qu trnh thu s c

k hiu l n~

s . Nh vy:

n

~

s - sn chnh l tn hiu nn. nhiu ca tn hiu c xc nh thng

qua nng lng o c ca tn hiu: E = 10log10N

0n

2

nn

~

N

0n

2

n

ss

s

(n v nng lng tnh bng dB)

Nh vy, nu nng lng E cng ln th n~

s cng gn vi sn, tn hiu nn

c gi tr gn v 0. Nu E th tn hiu thu c l tn hiu sch, khng c

nhiu.

3.2.2.4 Thng s n nhiu.

Cch xc nh: Thng bo yu cu ngi s dng dng ni trong 3

giy v thu tn hiu trong thi gian ly ting n nhiu ca mi trng

xung quanh. Ngng im lng c xc nh l nng lng cao nht ca cc

frame. Ngoi ra c th dng bin i Fourier tnh ra cc tn s nhiu phc

v cho vic lc nhiu.

3.2.2.5 Lc nhiu

Hin ti, vic lc nhiu ca h thng c thc hin theo phng php

kinh in l dng php bin i Fourier vi thut ton FFT. Dng bin i

Fourier thun xc nh c cc tn s tham gia v loi i tt c tn s khng

thuc phm vi ting ni (nu bit c phm vi tn s ng ca ngi s dng

th kt qu lc s cng cao) bng cch cho cc h s tng ng gi tr zero sau

bin i ngc li.

35

3.2.3 Mt s k thut kh nhiu

1. K thut CMS

y l mt k thut thng dng kh nhiu trong cc h thng nhn

dng, c dng kt hp trong qu trnh tnh ton cc c tnh ph ca ting

ni. Phng php ny da trn gi thit l cc c tnh tn s ca mi trng

l thng xuyn c nh hoc bin i chm. Cc tham s cepstral ca mt

pht m c tr i gi tr trung bnh ca cc tham s trong mt khong thi

gian no v lm cho cc gi tr ny t b nh hng bi mi trng

( ) = O( ) - 1t

)(OT

1 (3.2.1)

Trong , T l di ca vng ly gi tr trung bnh, thng l di

ca c pht m.

2. K thut RASTA

RASTA l k thut lc da trn gi thit rng cc tnh cht thi gian ca

cc nhiu l khc so vi cc tnh cht thi gian ca ging ni. Tc thay i

ca cc thnhphn khng phi ting ni thng xuyn nm ngoi tc hot

ng ca b my pht m con ngi. Bng cch dng b lc s, k thut

RASTA c th loi b c mt phn cc nhiu ca mi trng v cc nhiu

b sung bt thng khc. B lc dng trong RASTA l:

H(z) = 1

321

z94,01

z1,0z2,0z1,02,0 (3.2.2)

Cc k thut kh nhiu thng yu cu mt on ting ni ln

phn tch, thng k. V vy, khi p dng cc k thut kh nhiu vo nhn dng

ting ni, cn lu n tc x l v bo tn cc c trng m hc ca ph

m, c bit l cc ph m v thanh. m bo thc hin c trong thi

gian thc, hin nay, ngi ta p dng m hnh tham s thch nghi vi nhiu. C

th nh sau: Khi hun luyn tham s, ngi ta ly mt mu sch, khng b

nhiu, hun luyn, sau , ngi ta ly cc mu sch ny trn vi cc loi

nhiu sinh bi cc m hnh ton hc khc nhau v tham s m hnh s c

bin i bi mu nhiu nh cc cng c m hnh nh mng Nron. Do ,

36

trong giai on nhn dng, khi tn hiu thc c a vo h thng, ngi ta s

tnh thng cc c trng v quyt nh t chnh tn hiu ch khng cn lc

3.2.4 Mt s phng php nhn dng ting ni

3.2.4.1 S khi h thng nhn dng ting ni

Qu trnh nhn dng ting ni c th m t s lc nh sau: m thanh

mi a vo my s c phn tch trch ra cc c trng ca ting ni,

ngn ng. Sau em so snh vi cc mu ta thc hin phn tch t trc.

Cui cng l a ra quyt nh nhn dng i vi m thanh mi. So snh mu

thc hin tnh ton v quyt nh cho nhn dng ting ni.

H thng so snh mu

Vi h thng so snh mu, y ch l m t mt cch khi qut nht

cho mt ng dng nhn dng ting ni. Di y l s khi cho h thng

nhn dng ting ni theo tng t ring bit.

Trch

c trng

Quyt nh

nhn dng

Cc mu

so snh

u vo

m thanh

u ra kt

qu nhn

dddng

Trch

c trng

Quyt nh

nhn dng t

Cc t mu

so snh

u vo

m thanh

u ra kt

qu nhn

dng

37

H thng ny c nhiu kh nng thc hin. Nhng i vi mi mt

ngn ng s lng t thng l rt ln. Vic thit lp v lu tr h thng d

liu cho tt c cc mu t trong mt ngn ng gp nhiu kh khn v dung

lng b nh cng nh tc x l thc. nng cao tnh kh thi ca h

thng ny, ngi ta b xung thm mt khu nhn dng n gin : nhn dng

m v. Mt t in m v c xy dng thc hin nhn dng m v ca t.

Sau da trn kh nng m v s sinh ra t no v tip tc nhn dng t .

im khc bit l ch trong t in mi t l mt chui cc m v cu thnh

ln t . Nh kch thc ca t in t nh hn, gim c dung lng

b nh dnh cho t in t.

Nhn dng t da trn nhn dng m v

3.2.4.2 So snh tng ng gia cc mu

Ngy nay nhn dng ting ni tr nn pht trin v c ng dng

rt nhiu trong cuc sng, c nhiu phng php nghin cu v nhn dng

ting ni nh phng php m hnh markow n (HMM), phng php dng

mng nron , hay phng php LPC-10

Trong vn nhn dng d l nhn dng nh, m thanh hoc mt kiu

d liu no khc, hay m hnh nhn dng no th vic ra quyt nh u da

trn phng php chung nht l so snh. i chiu gia mu mi v cc lp

mu sau da trn cc quy tc quyt nh v mu . Mu no c

tng ng i vi 1 lp mu l ln nht th quyt nh mu thuc v lp

mu .

Trch

c trng

Cc t

mu so

snh u vo

m thanh

u ra kt

qu nhn

dng

Nhn dng

t

Nhn dng

m v

Cc m v

mu so

snh

38

3.2.4.2.1 nh ngha

tng ng( hay ging nhau) gia cc mu c xc nh bng

cng thc ton hc. N cho php ta khng nh s ging nhau ca 2 mu.

Gi s ta c 2 vector mu u v Ai , Aj n chiu. ging nhau L(Ai ,

Aj) phi tho mn cc iu kin sau:

- S o ging nhau phi dng : L(Ai , Aj) >= 0;

- Phi c tnh i xng L(Ai , Aj) = L(Aj ,Ai)

- S o ging nhau phi c gi tr cc i khi c lng s ging

nhau gia mt nh no vi chnh n

L(Ai , Aj) = max L(Ai , Aj) (vi mi i j)

3.2.4.2.2 Hm khong cch

Hm khong cch ca hai mu c th cho ta nh gi c d dng

ging nhau gia hai mu. Theo trc quan chng ta khng nh ging nhau

gia hai mu cng ln khi v ch khi khong cch gia chng cng nh.

Gi s hai mu Ai , Aj n chiu :

Ai = {ai1 , ai2 , ... , ain}

Aj = {aj1 , aj2 , ... , ajn}

Di y l mt s hm khong cch ph bin.

+ Khong cch clid

d1(Ai , Aj) = 1/2

N

1k

2

jkik })aa({ (3.2.3)

+ Khong cch Manhattan

d2(Ai , Aj) = N

1k

jkik aa (3.2.4)

+ Khong cch Trebsep

d3(Ai , Aj) = )aa(max jkikk

(3.2.5)

+ Khong cch Micowskiedo

39

d4(Ai , Aj) =

N

1k

1/

jkik aa (3.2.6)

+ Khong cch Korelasi

d5(Ai , Aj) = 1/2N

1k

2

jjk

N

1k

2

iik

N

1k

jjkiik

aa.aa

aaaa

(3.2.7)

y:

ia =

N

1k

ikxN

1 ja =

N

1k

jkxN

1

+ Khong cch Cambera:

d6(Ai , Aj) =

N

1k jkik

jkik

aa

aa

(3.2.8)

Cc hm tnh khong cch Trebsep, Manhattan v clid c khi

lng tnh ton tng dn. Cc hm cn li u i hi thi gian tnh nhiu

hn. Trong ba khong cch c khi lng tnh ton t nht th khong cch

clid m bo khc phc c c tnh bin ng ca mu ( m d liu tn

hiu m thanh c s bin ng rt ln v v bin v thi gian). La chn

hm tnh khong cch clid gim ti thiu tnh bin ng ca d liu m

thanh m vn m bo tc tnh ton cho h thng.

3.2.4.2.3 Nhn dng trn c s tng ng ca cc i tng

Gi s ta c S = {S j} l tp cc mu nhn dng N chiu. Vic nhn

dng s c thc hin thng qua cc s o v tng ng gia mu mi

vi cc mu c.

Ai thuc S j nu L(Ai, S j) = max (L(Ai, S j)) theo j

Theo quan im v khong cch :

Ai thuc S j nu d(Ai, S j) = min (L(Ai, S j)) theo j

Nh vy ta c th vn dng nhn dng mu theo nguyn tc :

+ Tnh khong cch gia mu mi vi tng lp mu khc nhau.

40

+ Khng nh mu thuc lp no c tr khong cch l nh nht.

3.2.4.3 i snh mu da trn phng php LPC-10

Phng php ny c p dng nhn dng cc t n l. N c cc u

v nhc im sau:

u im:

- Tiu hao ti nguyn h thng t

- C th s dng cho mt t n hoc mt nhm t m khng cn thay

i thut ton nhiu.

- D ci t v trin khai. Vi s lng t khng ln, chnh xc t

cao.

Nhc im:

- chnh xc ca h ph thuc vo s lng mu hc. Cc mu tham

kho s b nh hng bi mi trng lc to mu nh ting n, thit b,

tm l...

- Thi gian tnh ton ph thuc vo s lng mu hc v s lng t

cn nhn dng

3.2.4.3.1 Phn tch d bo tuyn tnh

Phn tch d bo tuyn tnh l mt trong nhng k thut phn tch ting

ni c s dng rng ri. N c th tnh ton hiu qu cc tham s nh hm

din tch ca tuyn m v lu tr hoc truyn thng ting ni vi t l lu tr

nh.

Phn tch d bo tuyn tnh da trn c s mu tn hiu yn s c d

bo bng p mu tn hiu trc n.

41

yn

p

1i

ini y + G . n

Trong : i (i=1..p) l cc h s d bo

{yn-i}(i=1..p) l dy p tn hiu ngay trc ca tn hiu yn

G : h s lc lp

n : sai s d bo (hay cn gi l nhiu)

Sai s d bo n chnh l sai s phn tch ting ni. Yu cu t ra cho

h thng l phi gim ti thiu sai s d bo n . y ta thc hin o hm

ring phn n2 cho tng bin i (i=1..p), tnh gi tr h s d bo i m vi

gi tr n2 t cc tiu.

0

2

1

P

i

ninin

j

.Gy.yE

=> 0..21

jn

P

i

ninin yGyyE

=>

P

i

jnnjnini yyEyyE1

][][

Bi ton a v gii h phng trnh P n tm i . gii h trn ta

cn tnh c cc E [yn-i . yn-j]. C hai phng php cho php ta tnh cc E [yn-

i . yn-j] l phng php t tng quan (autocorrelation) v phng php hip

bin (autocovariance). Trong phng php t tng quan ta c :

E [ yn-i . yn-j] = Ryy(| i j |)

42

Gi s dy tn hiu {yn} bng 0 ngoi on tn hiu ta cn tnh h s d

bo. Khi :

N

kn

knn yyk1

.)(yyR

By gi ta c th m t h phng trnh dng ma trn nh sau :

)(

...

)2(

)1(

....

)0(...)2()1(

............

)2(...)0()1(

)1(...)1()0(

2

1

PR

R

R

RPRPR

PRRR

PRRR

yy

yy

yy

Pyyyyyy

yyyyyy

yyyyyy

H phng trnh trn c th gii bng phng php nghch o ma trn

bi v ma trn Ryy l ma trn Toeflitz (ma trn i xng qua ng cho

chnh v cc ng cho song song vi ng cho chnh c cc phn t

ging nhau). Ma trn Toeflitz lun c nh thc khc 0, cng c ngha l lun

tm c ma trn nghch o cho ma trn Toeflitz. Nhng gii h phng

trnh bng phng php ma trn nghch o khng hiu qu, hn na sai

s rt ln. Di y trnh by thut ton Levinson Durbin cho php ta tnh

h s d bo i (i=1..P) m khng cn gii h phng trnh trn.

* Thut ton Levinson Durbin :

1. t E0 = Ryy(0) , i = 0

2. i = 1

3. ki = (

1

1

1

)1(/))()1(

i

j

iyyyy

i

j EiRjiR )

4. t i(i)

= ki

5. j(i)

= j(i-1)

+ ki . j(i-1)

(vi j = 1..i-1)

6. Ei = ( 1 ki2 ) Ei-1

7. Nu i < P th quay li 2.

43

3.2.4.3.2 Nhn dng ting ni bng phng php LPC-10

LPC l vit tt ca Linear Predictive Coder (m ho d bo tuyn tnh).

Ch s 10 c ngha l h thng d bo tuyn tnh c s lng h s t 10 tr

ln l tt nht, h thng phi c ti thiu 10 h s d bo mi m bo mc

chnh xc ca kt qu d bo. S lng h s cng cao th hiu qu d bo

cng cao. Nhng ngc li thao tc tnh ton cng phc tp v tn nhiu thi

gian. Chng trnh nhn dng t ting Vit chn s lng h s LPC-10 l 10

h s. Qua thc nghim, tiu chun LPC-10 c c cc h s tt nht nu ta

ly kch thc frame t 10 20 ms(dng file WAVE 11.025kHz, mono, 8

bits, th kch thc theo mu tn hiu ca 1 frame t 110 n 220 mu). K

thut nhn dng ting ni bng phng php LPC-10 l thc hin tnh ton

cc h s d bo tuyn tnh sau so snh vi b mu l cc b h s d bo

c tnh ton trc .

X l tn hiu m thanh bng phng php d bo tuyn tnh (LPC) rt

ph bin. N p ng c cc yu cu t ra v x l m thanh: Tng hp

ting ni, nhn dng ting ni ... Nhn dng ting ni da trn tiu chun

LPC-10 chnh l vn dng k thut d bo tuyn tnh nhm tng hiu qu

nhn dng chng trnh.

44

CHNG 4: CHNG TRNH DEMO

4.1. Thit k cc chc nng chnh

Vi nhim v n l nghin cu v xy dng chng trnh nhn dng

t trong ting Vit. Trc ht, chc nng chnh ca chng trnh l m phng

c cng vic nhn dng cc t n ca ting Vit. N l c s cho vic

nhn dng cc n v ting Vit ln hn nh: t ghp, cm t, cu Chng

trnh gm 2 chc nng chnh:

+ Hun luyn h thng: Chc nng ny nhm mc ch to v cp nht

vo c s d liu cc c trng c bn nht ca t, tc l cho my hc

trch rt cc c trng ca t i vi nhiu ngi ni, phc v nhu cu

nhn dng t cho nhiu ngi khc nhau. Mi ngi thc hin cho my hc

mt s t ting Vit v sau s ghi m t nhng ln ni khc ri cho h

thng nhn dng.

+ Nhn dng t n (t ch c mt ting) ca ting Vit t file ngun:

Mt t ch c nhn dng sau khi cho my hc v t , chc nng ny

nhm nhn dng cc t t file m thanh. Nu cha c ta phi ghi m t cn

nhn dng bng trnh SoundRecorder ca Window tch hp sn trong h

thng ri ghi vo cc file Wave, sau vi nhn dng cc file m thanh ny

bng chc nng nhn dng ca chng trnh. Hoc kim tra kh nng nhn

dng chng trnh ta s dng cc t ghi m sn trong th mc Data-for-

NhanDang, do cc t ny c mt tp hp cc mu c hc trc v

lu cc c trng ca cc t trong c s d liu.

+ Nhn dng trc tip qua Microphone: Trn c s t c hc

ri. H thng s thng trc ch ngi ni ni vo Micro v hin th thng

tin nhn c dng text ln mn hnh. ng thi sng m c hin th trc

quan trong hp nh.

+ Ngoi ra cn c cc chc nng khc nh:

- Ghi m: ghi m cc t mu hc v cc t nhn dng.

- Hin th thng tin v file Wave ang c.

45

- Hin th sng m thanh khi c t tp.

- Hin th sng m thanh sau khi c x l.

- a ra loa d liu m thanh ang x l ( kim tra).

4.2. La chn ngn ng lp trnh

Trong thit k chng trnh nhn dng t ting Vit, chng trnh phi

c d liu m thanh vo mng. Sau phi thc hin x l d liu m thanh

thu c qua nhiu cng on a v dng chun ho v tnh ton a ra

b tham s c trng. Tip m c s d liu v so snh vi tt c cc mu

trong ri a ra kt lun nhn dng, cui cng l hin th t nhn dng

c. nhn dng c mt t phi x l rt nhiu thao tc, c bit khi s

lng t trong c s d liu ln.

Do s phc tp ca h thng v yu cu ca n, ti la chn ngn

ng Visual Basic vi h qun tr c s d liu Access. Ngn ng lp trnh ny

tuy c tc x l khng cao lm nhng li h tr ngi lp trnh tt trn c

s d liu v c giao din thn thin, d s dng. l ngn ng c kh

nng p ng c yu cu ca h thng.

4.3. Xy dng b mu nhn dng

M hnh nhn dng t ting Vit da trn phng php d bo tuyn tnh

LPC-10. Mi mt mu t s c chia thnh cc frame nh. Sau thc hin

tnh ton h s LPC-10 cho tng frame, cho tt c cc frame, b tham s ny

s c lu tr trong c s d liu.

Ta c th hnh dung thao tc to d liu t 1 mu nh sau :

+ File m thanh c ct trch ly phn d liu m thanh c ting

ni.

+ Chun ho thi gian

+ Chun ho bin ng

46

+ Chia file m thanh ra thnh 30 frame nh (kch thc mi frame 110

byte). Tnh h s LPC-10 cho mi mt frame. Sau lu tr b h s ny

trong c s d liu.

4.4. Mt s hnh nh ca chng trnh

Lc quan h c s d liu ca chng trnh

D liu c t chc gm 4 bng:

+ Bng 1 l bng chnh: gm 2 trng, trng th nht l kha ID

autonumber. Trng th 2 c dng text lu mu k t ca t c hc.

+ 3 bng cn li, mi bng gm mt trng kha ID v 100 trng

dng s double lu 30 b h s LPC-10 (mi b h s LPC-10 gm 10 s

c trng, 30 b h s l 300 con s tng ng vi 300 trng ca tng 3

bng).

Cc trng ID ca c 4 bng c lin kt vi nhau. Quan h gia cc

bng l 1-1. Mi mu m thanh c hc (1 t c hc) c lu vo CSDL

l 1 bn ghi vi ch s ID, tn, v 300 con s c trng. Do s trng lu tr

l rt ln nn ta tch ra thnh 4 bng

47

Hun luyn h thng hc cc t ting vit

Giao din gm hp nh th nht, v sng m thanh ca file m thanh

c m hc. Hp nh bn di hin th sng m thanh sau khi ct

ly phn ch c ting ni. Mc ch trc quan ho d liu ct c. Mt hp

TextBox nhp t cn hc. Ngoi ra cn hin th thng tin v file m thanh,

pht ra loa tn hiu m thanh khi mt file m thanh c m.

48

Nhn dng t ting vit t file ngun

Nhn dng t ting Vit t Microphone

49

NH GI KT QU V KT LUN

Vi ti c giao, sau thi gian thc hin n tt nghip, vn dng

nhng kin thc c bn c hc cng vi n lc bn thn, s ch bo tn

tnh ca gio vin hng dn - Thc S V Vn Tng n Nhn dng tp

t hn ch Ting Vit trong mi trng nhiu hon thnh. Chng

trnh p ng c c bn cc yu cu t ra.

Nhng vn t c:

+ p ng c tn ti yu cu l nhn dng t ting vit

+ Khi s lng mu hun luyn ln th kt qu nhn dng t cht

lng

+ Th nghim h thng cho kt qu nhn dng tt khi m s lng t

khng ln (hn 20 t).

+ H thng nhn dng tt vi cng ngi ni v nhng ngi tham gia

hun luyn mu.

+ Khi ngi ni khng tham gia hun luyn mu th kt qu nhn dng

cha c kh quan.

Cc yu cu ca tng cht lng h thng

+ Chn mu hun luyn phi l cc mu chun, t nhiu

+ Tng s lng mu hc

+ Kim tra, nghe th trc khi cp nht vo CSDL

Hng pht trin ca n

+ Lm c s thit k h thng nhn dng cm t v cu

+ Pht trin chng trnh giao tip vi my tnh trc tip qua

Microphone thc hin mt s cu lnh c bn.

50

TI LIU THAM KHO

+ Visual Basic 6 Certification Exam Guide Chaper 1- Dan mezick &

Scot Hillier Mcgraw- Hill 1998.

+ Digital Signal Processing: Principles, Algorithms, and

Applications- Prentice Hall. John G. Proakis, Dimitris G. Manolakis

+ X l tn hiu v lc s - Nguyn Quc Trung.

+ Visual Basic - Lp trnh c s d liu- Nxb Lao ng x hi-2004-

Nguyn Th Ngc Mai.

+ Digital Signal Processing: A Computer-Based Approach-

McGraw-Hill. Sanjit K. Mitra

+ X l tn hiu s- Nguyn Hu Phng.

+ Ti liu tham kho mn hc X l ting ni [L B Dng- khoa

CNTT- H Hng Hi Vit Nam].

+ Voice Processing - Gordon E. Pelton nm 1993.