Do an Tot Nghiep Xu Ly Tieng Noi 156

7/31/2019 Do an Tot Nghiep Xu Ly Tieng Noi 156

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N TT NGHIP

TI

X L TING NI

SVTH: NGUYN TH NGC DIP


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CNG HA X HI CH NGHA VIT NAM

c lp T do Hnh phc

LI CAM OAN

Knh gi: Hi ng bo v n tt nghip Khoa in t _ Vin thng _

Trng i hc Bch Khoa Nng.

Em tn l: Nguyn Th Ngc Dip

Hin ang hc lp 04T1- Khoa: in t - Vin thng Trng: i hc

Bch Khoa Nng.Nhm em xin cam oan ni dung ca n ny khng phi l bn sao chp

ca bt c n hoc cng trnh c t trc.

Sinh vin thc hin

Nguyn Th Ngc Dip

SVTH: Nguyn Th Ngc Dip Trang 2

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MC LC

LI CAM OAN.....................................................................................................2

MC LC................................................................................................................3

DANH MC CC T VIT TT V CC THUT NG TING ANH...........5

M U..................................................................................................................7

CHNG 1: TNG QUAN V NNG CAO CHT LNG TING NI......11

CHNG 2 : NH GI CHT LNG TING NI.....................................28

CHNG 3: THUT TON SPECTRALSUBTRACTION V WIENER

FILTERING............................................................................................................39

CHNG 4: THC HIN V NH GI CC THUT TON.....................52

KT LUN N V HNG PHT TRIN TI..................................74

PH LC...............................................................................................................75

DANH MC CC HNH V V BNG

Hnh 1.1 Tn hiu ting ni [2]...............................................................................13

Hnh 1.2 Dng v s phn b ph nng lng trung bnh nhiu trn xe [4]...........16Hnh 1.3 Dng v s phn b ph nng lng trung bnh ca nhiu trn tu [4]...16

Hnh 1.4 Dng v s phn b ph nng lng trung bnh ca nhiu trong nh

hng[4]....................................................................................................................17

Hnh 1.5 Mc nhiu v ting ni (c o bng SPL dB) trong cc mi trng

khc nhau [4]...........................................................................................................18

Hnh 1.6 Mu ting ni eee c ly mu vi tn s ly mu 8kHz [11]...........23


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Hnh 1.7 Dng sng tn hiu ting ni ca cu The wife helped her husband v

dng sng ca ph m f trong t wife, dng sng ca on nguyn m er

trong t her [11]..................................................................................................25

Hnh 1.8 mt ct dc ca c quan to ting ni [11]..............................................26

Hnh 1.9 m hnh k thut to ting ni[11]...........................................................26

Hnh 1.10 bng phn loi m v trong ting Anh ca ngi M [11].....................27

Bng 2.1.Thang im nh gi cht lng ting ni theo MOS [12].....................29

Bng 2.4. Thang im nh gi cht lng tn hiu ting ni theo CCR...............30

Bng 2.5. Thang nh gi DCR..............................................................................30

Hnh 3.1 S khi cho hai thut ton SS v WF.................................................39

Hnh 3.2 S khi ca thut ton Spectral subtraction [26]................................43

Hnh 3.3 S khi ca thut ton Wiener Filtering.............................................46

Hnh 3.4 Phn tch tn hiu thnh cc frame [31]...................................................47

Hnh 3.5 qu trnh thc hin overlap v adding [32]..............................................48

Hnh 4.1. S thc hin v nh gi thut ton tng cng................................53

Hnh 4.2 Lu thut ton SS................................................................................55

Hnh 4.3 Lu thut ton WF..............................................................................56

Hnh 4.4 dng sng v spectrogram ca tn hiu sch............................................57

Hnh 4.5 Dng sng v ph ca tn hiu b nhiu xe hi vi SNR = 10dB............57Hnh 4.6 Dng sng v spectrogram ca tn hiu sau khi x l nhiu xe hi bng

SS vi SNR = 10dB................................................................................................58

Hnh 4.7 Dng sng v spectrogram ca tn hiu sau khi x l nhiu xe hi bng

WF vi SNR = 10dB...............................................................................................58

Hnh 4.8 Quy trnh thc hin nh gi....................................................................60

Hnh 4.9. th kim tra n nh ca nh gi OE i vi nhiu xe hi ........61


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Hnh 4.10. th kim tra n nh ca nh gi OE i vi nhiu ngi ni

xung quanh .............................................................................................................61

Hnh 4.11 th nh gi Objective vi h s IS=0.2, NoiseMargin=3................63

Hnh 4.12 th nh gi Objective vi h s IS=0.15, NoiseMargin=2..............64

Hnh 4.14 th nh gi objective vi h s alpha=0.5, 0.8,0.9 vi IS=0.15 v

NoiseMargin = 2.....................................................................................................66

Hnh 4.15 th nh gi objective vi h s gamma = 1 v gamma = 2.............67

Hnh 4.16 th nh gi vi IS=0.15 NoiMargin= 2 v alpha = 0.8 cho thut ton

WF, gama=1 cho thut ton SS...............................................................................69

Hnh 4.17 th nh gi OE vi nhiu ngi ni xung quanh............................70

DANH MC CC T VIT TT V CC THUT NG TING

ANH

T vit

ttTing Anh Ngha ting Vit

SNR Signal Noise Ratio T s tn hiu trn nhiuPC Personal Computer My tnh c nhn


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SPL Sound Pressure Level Mc p sut ca m thanh

MMSE Minium Mean-Squared ErrorTi thiu ho sai lch trung

bnh bnh phngSVD Singular Value Decomposition Php phn tch gi tr nDFT Discrete Fourier Transform Php bin i Fourier ri rcFFT Fast Fourier Transform Php bin i Fourier nhanh

DTFT Discrete-Time Fourier TransformPhp bin i Fourier ca tn

hiu ri rc.

ZT Z Transform Php bin i ZROC Region of Convergence Min hi t

IDTFTInverse Discrete Fourier

Transform

Php bin i ngc Fourier

ri rc

LTI Linear Time-InvariantH thng tuyn tnh v bt

bin theo thi gian

ITU-TInternationalTelecommunications

Union-Telecommunication

Hip hi tiu chun vin thng

quc tACR Absolute Categories Rating nh gi theo gi tr tuyt i

MOS Mean Opinion Scoresnh gi theo quan im

ngi ngheCCR Comparison Category Rating nh gi bng cch so snhDCR Degradation Category Rating nh gi suy gim cht lngSE Subjective Evaluation nh gi ch quanOE Objective Evaluation nh gi khch quanIS Itakura_SaitoLLR Log likehook RaitoWSS Weighted Spectral Slope o theo trng s ca phLPC Linear Prediction Coefficients H s d on tuyn tnh

VAD Voice Activity Detection

Thm d s hot ng ca

ting niSpeech Enhancement Nng cao cht lng ting ni

SS Spectral Subtraction

Thut ton gim nhiu tn hiu

ting ni bng phng php

tr ph.

WF Wiener Filter


ting ni bng cch s dng

b lc Wiener.


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Statistical-model-based


ting ni da trn nguyn l

thng k

FrameKhung tn hiu.

Hamming Ca s HammingOverlap v Adding Xp chng v cng

M U

Trong cuc sng, ting ni ng mt vai tr rt quan trng i vi con

ngi. Cng vi ting ni l s xut hin ca rt nhiu cc loi dch v thoi nh

ngy nay. Tuy nhin vic bo ton c tn hiu ting ni trn cc dch v ny l

iu v cng kh khn do s mt mt v suy gim tn hiu v nht l nh hng

ca nhiu s lm cho tn hiu ting ni khng cn nh ban u. V l do m cc

thut ton v Speech Enhancement ra i. Tuy khng th bo ton c y nguyn

tn hiu ban u nhng s dng cc thut ton ny ta c th tng cng c cht

lng ting ni v gim bt nhiu nn tn hiu sau khi x l n ngi nghe

vn mang y ni dung thng tin v khng gy kh chu bi nhiu i vi

ngi nghe. V vy, Speech Enhancement ng mt vai tr rt quan trng tronglnh vc thoi.

Xut pht t thc t ny nhm bt tay vo tm hiu v Speech

Enhancement, nghin cu cc thut ton ca n thc hin v nh gi hiu qu

ca cc thut ton trong mi trng thc t.

thc hin c n, nhm phn chia thnh 3 phn tng ng vi 3

thnh vin :


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- Nguyn Ngc Trung: nghin cu v thc hin thut ton x l ting ni s

dng phng php Spectral Subtraction.

- Nguyn Phc Nguyn : nghin cu v thc hin thut x l ting ni s

dng b lc Wiener.

- Nguyn Th Ngc Dip : nghin cu v thc hin cc phng php nh gi

t cc kt qu t c ca 2 thut ton trn trong mi trng thc t.

thc hin c ni dung phn ca em th n ca em c kt cu

thnh 2 phn, gm 5 chng :

Phn 1 : L thuyt

Chng 1 : Tng quan v nng cao cht lng ting ni. Chng ny gii

thiu mt s khi nim c bn v tn hiu s, cc php bin i, tm hiu v cc

loi nhiu , tn hiu ting ni v s hnh thnh ting ni. Bn cnh cn gii

thiu khi qut v mt s thut ton trong Speech Enhancement .

Chng 2 : nh gi cht lng ting ni. Chng ny gii thiu mt s

phng php nh gi hiu qu ca thut ton gim nhiu trong ting ni. Gm c

nh gi ch quan v nh gi khch quan.Chng 3 : Thut ton Spectral Subtraction v Wiener Filtering. Chng

ny i su vo nghin cu nguyn l c bn ca tng thut ton.

Phn 2 : Thc hin v nh gi

Chng 4 : Thc hin v nh gi thut ton. Chng ny trnh by cc kt

qu nhm lm c gm c thc hin gim nhiu tn hiu ting ni bng hai

thut ton nghin cu chng 3. ng thi so snh kt qu thu c bng

cch dng cc phng php nh gi c gii thiu chng 2

Phng php nghin cu ca n l xy dng lu ca thut ton, thc

hin x l ting ni bng cc thut ton . Da trn cc kt qu t c sau khi

x l, sau s dng cc phng php nh gi khch quan nh gi tnh hiu

qu ca cc thut ton x l trong mi trng thc t.

n ca nhm thc hin c 2 thut ton x l ting ni trong Speech

Enhancement v a ra c cc kt qu nh gi khch quan lm c s nh


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gi tnh hiu qu ca 2 thut ton trn. chnh l im mi trong n ca

nhm so vi cc n c trc trong cng ch nghin cu.


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Chng 1 : Tng quan v nng cao cht lng ting ni

CHNG 1: TNG QUAN V NNG CAO CHT LNG TING NI

1.1 Gii thiu chng

Ni dung ca chng trnh by mc ch ca nng cao cht lng ting ni

l g, cc loi nhiu trong ting ni, cch hnh thnh ca ting ni v cc c im

cu tn hiu ting ni. Chng ny cn gii thiu khi qut v cc thut ton s

dng trong speech enhancement.

1.2 Nng cao cht lng ting ni l g ?

Nng cao cht lng ting ni lin quan n vic ci thin cm nhn i vi

ting ni b suy gim cht lng do s c mt ca nhiu trong ting ni. Trong hu

ht cc ng dng, th mc ch ca nng cao cht lng ting ni l s ci thin

cht lng v tnh d nghe ca ting ni b suy gim do nhiu. S ci thin v

cht lng m tt th n lm gim i s kh khn cho ngi nghe khi nghe v

trong nhiu trng hp n cn gip cho ngi nghe c th nghe trong mi trng

c nhiu vi mc cao v nhiu tn ti trong thi gian di. Cc thut ton ng

cao cht lng ting ni lm gim v nn nhiu nn n mt mc no v nc xem nh l cc thut ton nn nhiu.

Trong nhiu trng hp, s cn thit ca vic tng cng trong tn hiu ting

ni xut hin khi tn hiu ting ni hnh thnh trong vng c nhiu hoc nh hng

bi nhiu trong cc knh truyn thng. C rt nhiu kch bn yu cu t ra i vi

Speech enhancement trong nhiu trng hp khc nhau, v d i vi thng tin

thoi, trn cc h thng in thoi t bo th chu s nh hng nhiu nn t t,

nh hng,.. khi truyn n ch. Chnh v vy m cc thut ton trong nng cao

cht lng ting ni c th c s dng ci thin cht lng ca ting ni ti

im thu, mt khc, n c th c s dng trong cc khi tin x l ca h thng

m ho ting ni dng trong cc in thoi t bo chun [1]. Khi nhn dng ting

ni, ting ni b nhiu c tin x l bi cc thut ton nng cao cht lng trc

khi c nhn dng. Trong thng tin lin lc hng khng, cc k thut nng cao

ting ni cn c s dng ci thin cht lng v tnh d nghe ca ting ni



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ca phi cng b nh hng bi nhiu trong bung li. V vy m nng cao cht

lng ting ni cng rt cn thit trong thng tin lin lc ca qun s. Trong h

thng hi ngh qua thoi, th ngun nhiu xut hin mt vng no th n s

c truyn n tt c cc vng khc. Cc thut ton nng cao cht lng ting ni

c s dng nh tin x l hoc lm sch nhiu trong ting trc khi c

khuch i.

Nh cc v d minh ha trn th mc tiu ca cc thut ton tng cng tu

thuc vo cc ng dng m chng ta ang dng. Xt trn phng din l tng,

th chng ta mong mun Speech enhancement ci thin c c cht lng v tnh

d nghe hay s trong sut ca ting ni. Tuy nhin, xt trn phng din thc t

th cc thut ton Speech enhancement ch c th ci thin c cht lng ca

ting ni. N c th lm gim c nhiu nn trong ting ni nhng n s lm gia

tng thm mo ca tn hiu ting ni, chnh iu ny lm gim i tnh d nghe

ca ting ni. Do , yu cu chnh trong vic thit k mt thut ton Speech

enhancement phi m bo nn c nhiu v khng c gy ra mo trong s

cm nhn tn hiu ting ni.Gii php tng qut trong cc vn ca Speech enhancement ph thuc rt

ln vo ng dng chng ta cn s dng, l cc vn nh l ngun nhiu v

giao thoa gy ra nhiu, mi lin h gia nhiu v tn hiu sch, s microphone v

cm bin c th c. S giao thoa c th xem nh l nhiu hoc c xem nh tn

hiu ting ni, n tu thuc vo mi trng ta ang xt, n c th c xem nh l

s tranh chp gia cc speaker. c tnh m nhiu c th c cng thm vo tn

hiu sch nu m thanh c hnh thnh trong cn phng b di m thanh. Hn

na, nhiu c th c tnh tng quan hoc khng tng quan v mt thng k vi

tn hiu sch. S lng microphone cng c kh nng nh hng n tnh hiu qu

ca cc thut ton Speech enhancement.



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1.3 L thuyt v tn hiu v nhiu

1.3.1 Tn hiu, h thng v x l tn hiu

1.3.1.1 Tn hiu

Tn hiu(signal) dng ch mt i lng vt l mang tin tc. V mt ton

hc, ta c th m t tn hiu nh mt hm theo bin thi gian, khng gian hay cc

bin c lp khc. Chng hn nh, hm: x(t) = 20t2 m t tn hiu bin thin theo

bin thi gian t. Hay mt v d khc, hm: s(x,y) = 3x + 5xy + y2 m t tn hiu l

hm theo hai bin c lp x v y, trong x v y biu din cho hai ta trong

mt phng [2].

Hai tn hiu trong v d trn v lp tn hiu c biu din chnh xc bng

hm theo bin c lp. Tuy nhin, trong thc t, cc mi quan h gia cc i

lng vt l v cc bin c lp thng rt phc tp nn khng th biu din tn

hiu nh trong hai v d va nu trn.

Hnh 1.1 Tn hiu ting ni [2].

Ly v d tn hiu ting ni l s bin thin ca p sut khng kh theo

thi gian. Chng hn khi ta pht m t away, dng sng ca n c biu din

nh hnh trn.

1.3.1.2 Ngun tn hiu

Tt c cc tn hiu u do mt ngun no to ra, theo mt cch thc no

. V d tn hiu ting ni c to ra bngg cch p khng kh i qua dy thanh



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m. Mt bc nh c c bng cch phi sng mt tm phim chp mt cnh/i

tng no . Qu trnh to tn hiu nh vy thng lin quan n mt h thng,

h thng ny p ng li mt kch thch no . Trong tn hiu ting ni, h thng

l h thng pht m, gm mi, rng, li, dy thanhKch thch lin quan n h

thng c gi l ngun tn hiu. Nh vy ta c ngun ting ni, ngun nh v cc

ngun tn hiu khc.

1.3.1.3 H thng v x l tn hiu

H thngl mt thit b vt l thc hin mt tc ng no ln tn hiu. V

d, b lc dng gim nhiu trong tn hiu mang tin c gi l mt h thng.

Khi ta truyn tn hiu qua mt h thng, nh b lc chng hn, ta ni rng x l

tn hiu . Trong trng ny, x l tn hiu lin quan n lc nhiu ra khi tn

hiu mong mun.

X l tn hiu l mun ni n mt lot cc cng vic hay cc php ton

c thc hin trn cc tn hiu nhm t mc ch no , nh l tch tin tc

cha bn trong tn hiu hoc l truyn tn hiu mang tin t ni ny n ni khc.

y ta cn lu n nh ngha h thng, n khng ch n thun l thitb vt l m cn l phn mm x l tn hiu hoc l s kt hp gia phn cng v

phn mm. V d khi x l s tn hiu bng mch logic, h thng x l y l

phn cng. Khi x l bng my tnh s, tc ng ln tn hiu bao gm mt lot cc

php ton thc hin bi chng trnh phn mm. Khi x l bng cc b vi x l-h

thng bao gm kt hp c phn cng v phn mm, mi phn thc hin cc cng

vic ring no .

1.3.1.4 Phn loi tn hiu

Cc phng php ta s dng trong x l tn hiu ph thuc cht ch vo c

im ca tn hiu. C nhng phng php ring p dng cho mt loi tn hiu no

. Do vy, trc tin ta cn xem qua cch phn loi tn hiu lin quan n nhng

ng dng c th. Chng ta c th phn tn hiu thnh cc loi :

- Tn hiu nhiu hng v tn hiu a knh

- Tn hiu lin tc v tn hiu ri rc



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- Tn hiu bin lin tc v tn hiu bin ri rc

- Tn hiu xc nh v tn hiu ngu nhin

1.4 L thuyt v nhiu

1.4.1 Ngun nhiu

Nhiu mt hin thc, n tn ti mi ni, trn ng ph, trn xe, trong vn

phng, trong nh hng, trong cc to nh. N c th l ting xe chy trn ng,

ting n trn cc cng trng xy dng, ting n pht ra t cc qut chy trong

PC, chung in thoi, n tn ti vi cc hnh dng v hnh thc khc nhau

trong cuc sng hng ngy ca chng ta.

Nhiu c th hnh thnh mt ni c nh, v khng thay i theo thi gian,

v d nh l ting n pht ra t qut chy trong PC. Nhiu cng c th khng ng

yn mt ch, v d nh nhiu trong nh hng, l ting ni ca nhiu ngi xen

ln vi nhiu cch khc nhau vi ting n pht ra t nh bp. Cc c tnh v ph

cng nh thi gian ca nhiu trong nh hng thay i khng theo quy lut nn vic

nn nhiu trong cc mi trng c nhiu thay i nh vy s kh khn hn nhiu

so vi cc ngun nhiu ng yn khng thay i.Cc c tnh c bit khc nhau ca cc loi nhiu l hnh dng ca ph

v s phn b ca nng lng nhiu trong min tn s. V d, nhiu gy ra bi gi

th nng lng ca n tp trung tn s thp di 500Hz. Nhng i vi nhiu

trong nh hng, trn xe, trn tu th khc, nng lng ca n c phn b trn

mt di tn s rng [3].



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Hnh 1.2 Dng v s phn b ph nng lng trung bnh nhiu trn xe [4].

Hnh 1.3Dng v s phn b ph nng lng trung bnh ca nhiu trn tu

[4].



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Hnh 1.4 Dng v s phn b ph nng lng trung bnh ca nhiu trong

nh hng[4].

1.4.2 Nhiu v mc tn hiu ting ni trong cc mi trng khc nhau

im ti hn trong vic thit k cc thut ton ca Speech enhancement l s

nhn bit di bin thin ca ting ni v mc cng nhiu trong mi trng

thc t. T , chng ta c th m t min bin thin ca mc t s tn hiu

trn nhiu(SNR) c bt gp trong mi trng thc t. iu ny rt quan trng

nh gi tnh hiu qu ca cc thut ton Speech enhancement trong vic nn

nhiu v ci thin cht lng ca ting ni trong di bin thin ca mc SNR.

Mc ca ting ni v nhiu c o lng bng mc m thanh. Phpo lng y l o mc p sut ca m thanh tnh bng dB SPL(sound

pressure level)[4]. Khong cch gia ngi ni v ngi nghe cng nh hng

n mc cng m thanh, n tng ng vi php o c thc hin khi

microphone c t ti nhng v tr c khong cch khc nhau. Khong cch c

trng trong giao tip face-to-face l 1m, khi khong cch tng gp i th mc

cng m gim i 6 dB[6].



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Hnh bn di ny l s tng hp v mc m trung bnh gia ting ni v

nhiu trong cc mi trng khc nhau. Mc ca nhiu nh nht trong cc mi

trng nh phng hc, trong nh , trong bnh vin v trong cc to nh. Trong

cc mi trng khc nhau, th mc m ca nhiu nm trong phm vi bin thin

t 50 n 55 dB SPL, v mc m ca ting ni l 60 n 70 dB SPL. V

khuyn ngh a ra l mc t s SNR c hiu qu trong cc mi trng ny l 5

n 15 dB. Mc m ca nhiu rt cao trong cc mi trng tu in ngm,

trn my bay, n t khong 70 n 75 dB SPL. V mc m ca ting ni trong

cc mi trng ny cng t mc , nn mc t s SNR trong cc mi trng

ny gn nh l 0 dB.

Hnh 1.5 Mc nhiu v ting ni (c o bng SPL dB) trong cc mi

trng khc nhau [4].

1.5 Tn hiu ri rc theo thi gian

Tn hiu ri rc theo thi gian x(n) c th to ra bng cch ly mu tn hiu

lin tc theo thi gian xa(t) vi chu k ly mu l Ts (tn s ly mu Fs = 1/ T). Ta

c

xa(t)|t=nT = xa(nT) = x(n) , - < n< (1.1)

Lu n l bin nguyn, x(n) l hm theo bin nguyn, ch nh ti cc gi tr

n nguyn. Khi n khng nguyn, th x(n) khng xc nh, ch khng phi bng 0.

Trong nhiu sch v x l tn hiu s, ngi ta quy c: khi bin nguyn th bin



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c t trong du ngoc vung v khi bin lin tc th c t trong du ngoc

trn. T y tr i, ta k hiu tn hiu ri rc l: x[n].[7]

Mt s tn hiu ri rc c bn

1.5.1 Tn hiu bc nhy n v

u[n] =

=

,0

0,)(

XXXP (3.24)

V v ch st

[.] tn hiu ti khong thi gian ang x l.

Trong phng trnh nu cho h s ta c th c lng c priSNR bng

postSNR . Trong thc t h s =0.98 rt tt cho cc tn hiu c SNR


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Chng 3 : Thut ton Spectral Subtraction v Wiener Filtering

x l no trc th tn hiu sau khi c bin i FFT s bin i nhanh, lc

chng ta khng th thc hin c cc thut ton x l trit nhiu trong tn hiu v

khi tn hiu c xem l ng.

Chnh v vy, tn hiu ca chng ta cn phi c phn tch thnh nhng

khung tn hiu(frame) lin tc trong min thi gian trc khi chuyn sang min tn

s bng bin i FFT. Khi tn hiu c phn tch thnh cc frame lin tc, th

trong tng frame, tn hiu ca chng ta s bin i chm v n c xem l tnh.

Nu tn hiu c phn tch theo tng frame th khi cc thut ton x l trit

nhiu trong tn hiu mi c th thc hin c mt cch hiu qu. V cch phn

tch tn hiu ca chng ta l frame by frame.

thc hin vic phn tch tn hiu thnh cc frame, cn s dng cc loi

ca s thch hp. y, chng ta s dng ca s Hamming, vi N = 256 mu

trong tng frame :

1,...,0,)/)12cos((.85185.01 =+ NkNk (3.27)

Hnh 3.4 Phn tch tn hiu thnh cc frame [31].

1.19.2 Overlap v Adding

Sau khi phn tch tn hiu thnh cc frame lin tc trong min thi gian bng

ca s Hamming, nu cc frame ny lin tc vi nhau v khng theo mt iu kin

no c th khi thc hin bin i FFT th v tnh chng ta lm suy gim tn hiu

do Hamming l ca s phi tuyn.


N : kch thc ca frame

m : s lng frame


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Nn khi thc hin phn tch tn hiu thnh cc frame th yu cu t ra l cc

frame phi sp xp chng ln nhau, gi l overlap. Vic xp chng cc frame

vi nhau s c thc hin theo mt t l chng lp thch hp, thng thng l

40% hoc 50%.

Sau khi cc frame tn hiu c x l trit nhiu trong min tn s, cc

frame ny c lin kt li nhau bng phng php thch hp vi phng php

phn tch tn hiu thnh cc frame u vo gi l adding.

Tp hp cc mu tn hiu trong cng mt frame sau khi c phn tch u

vo gi l mt segment. Vi cch thc hin phn tch v lin kt cc frame bng

phng php overlap v adding th tn hiu ca chng ta thu c sau khi x l

trit nhiu s khng b mo dng v s khng xut hin hin tng gi nhiu.

Hnh 3.5 qu trnh thc hin overlap v adding [32].

1.20 c lng v cp nht nhiu

Phng thc c lng nhiu c th nh hng ln n cht lng ca tn

hiu sau khi c tng cng. Nu nhiu c c lng qu nh th nhiu s vn

cn trong tn hiu v n s c nghe thy, cn nu nh nhiu c c lng

qu ln th ting ni s b mo, v lm s lm tnh d nghe ca ting ni b nh

hng. Cch n gin nht c lng v cp nht ph ca nhiu trong on tn

hiu khng c mt ca ting ni s dng thut ton thm d hot ng ca ting



49/75


ni (voice activity detection - VAD). Tuy nhin phng php ch tho mn i

vi nhiu khng thay i(nhiu trng), n s khng hiu qu trong cc mi trng

thc t (v d nh nh hng), nhng ni c tnh ph ca nhiu thay i lin

tc. Trong mc ny chng ta s cp n thut ton c lng nhiu thay i

lin tc v thc hin trong lc ting ni hot ng, thut ton ny s ph hp mi

trng c nhiu thay i cao.

1.20.1 Voice activity detection

Qu trnh x l phn bit khi no c ting ni hot ng, khi no khng

c ting ni (im lng) c gi l s thm d hot ng ca ting ni Voice

activity detection (VAD). Thut ton VAD c tn hiu ra dng nh phn quyt

nh trn mt nn tng frame-by-frame, khi frame c th xp x 20-40 ms. Mt

on ting ni c cha ting ni hot ng th VAD = 1, cn nu ting ni khng

hot ng hay chnh l nhiu th VAD = 0.

C mt vi thut ton VAD c a ra da trn nhiu c tnh ca tn hiu.

Cc thut ton VAD c a ra sm nht th da vo cc c tnh nh mc nng

lng, zero-crossing, c tnh cepstral, php o khong cch ph Itakura LPC,php o chu k.

Phn ln cc thut ton VAD u phi i mt vi vn l iu kin SNR

thp, c bit khi nhiu b thay i. Mt thut ton VAD c chnh xc trong

mi trng thay i khng th trong cc ng dng ca Speech enhancement,

nhng vic c lng nhiu mt cch chnh xc l rt cn thit ti mi thi im

khi ting ni hot ng [26].

1.20.2 Qu trnh c lng v cp nht nhiu

Nhiu s c c lng lc ban u bng cch ly trung bnh bin ph

ca tn hiu b nhiu

=

=1

0

)(1

)(M

i

ii YM

D (3.28)

Sau , s dng phng php VAD nhn bit cc frame tip theo, frame

no l frame nhiu v s cp nht nhiu cho cc frame tip theo. c th nhn



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bit c frame no l nhiu th chng ta thc hin so snh bin ph ca nhiu

c c lng vi bin ph ca tn hiu b nhiu :

dD

YT

i

i

= |)(

)(|

21

log201

(3.29)

Nu dBT 12 th frame khng phi l frame c ting ni, khi ta c

th cp nht li nhiu c c lng trc .

1.21 Kt lun chng

Ni dung ca chng gip nguyn l chung ca thut ton Spectral

Subtraction v Wiener Filtering. hai thut ton c th thc hin c th cn

phi phn tch tn hiu thnh cc frame v cc frame phi xp chng ln nhau, v

sau khi cc frame c x l trong min tn s v chuyn i v li min thi gian

th cc frame phi c lin kt li vi nhau theo ng phng php tng ng

vi phng php phn tch tn hiu u vo, qu trnh gi l overlap v

adding. Chnh iu s lm cho tn hiu ca chng ta sau khi x l trit nhiu s

khng b mo, m bo cht lng ca ting ni. Ni dung ca chng cng trnh

by vn c lng nhiu, y l ci chnh m speech enhancement cn giiquyt, n quyt nh tnh hiu qu ca thut ton v cht lng ca ting ni sau

khi x l trit nhiu.



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52/75

Chng 4: Thc hin v nh gi cc thut ton

CHNG 4: THC HIN V NH GI CC THUT TON

1.22 Gii thiu chng

Da vo l thuyt nghin cu c, chng ny xy dng cc lu

thut ton v thc hin cc thut ton gim nhiu m phng bng Matlab, sau

nh gi cc kt qu thu c ch yu bng phng php nh gi Objective

Measure



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1.23 Quy trnh thc hin v nh gi thut ton

Hnh 4.1. S thc hin v nh gi thut ton tng cng

Xy dng thut ton : da trn cc c s ton hc, cc php bin i trong

min thi gian v tn s i vi x l tn hiu s xy dng nn cc thut ton

x l nhiu trong ting ni.


Xy dng cc thut ton

Trin khai thut ton trn Matlab

Thc hin x l ting ni bngcc thut ton gim nhiu

Thc hin cc thut ton nh gida trn cc kt qu t c sau

khi x l

Nhn xt nh gi


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Trin khai trn Matlab: t thut ton xy dng c, thc vit m ngun

bng ngn ng lp trnh v s dng cc cng c trn Matlab to nn chng trnh

thc hin x l nhiu trong ting ni trn nn Matlab.

Thc hin x l ting ni bng cc thut ton: thc hin x l trit nhiu

trong cc file m thanh b nhiu bng chng trnh xy dng trn.

Thc hin cc phng php nh gi da trn cc kt qu t c sau khi

x l : sau khi cc file m thanh b nhiu vi cc mc v loi nhiu khc nhau

c x l trit nhiu, cng vi cc file m thanh sch tng ng, ta s dng

cc phng php nh gi ca Speech enhancement thc kim tra, nh gi tnh

hiu ca thut ton.

Nhn xt nh gi: t cc kt qu sau khi thc hin cc phng php nh

gi c trn, a ra cc kt lun nh gi : thut ton no thch hp cho loi

nhiu no, vi mc bao nhiu, thut ton no c kh x l nhiu tt hn trong

mi trng hp.



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1.24 Lu thut ton Spectral Subtraction

Hnh 4.2 Lu thut ton SS


Tnh li mc nhiu N

End

I=I+1;nhp frame tip theo

Begin

Phn chia Frame tn hiu uvo

Tinh cong suat nhieu trung binh N banu

I=0;Nhp frame u tin

VAD

X(:,i)=Beta*Y(:,i)

D=YS(:,i)-N; % Thc hin tr ph

X(:,i)=max(D,0);

Y=bin i FFT cho cc frame

X =

X =

=

X =

S

SpeechFlag==0?

S

I


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1.25 Lu thut ton Wiener Filtering

Hnh 4.3 Lu thut ton WF


Tnh li mc nhiu trung bnh

N

End

I=I+1;nhp frame tip theo

Begin

Phn chia Frame tn hiu u

vo

Tinh cong suat nhieu trung bnh N ban

u

SpeechFlag==0?

I=0;Nhp frame u tin

VAD

Tnh Priori SNR

Y=bin i FFT cho cc frame

Tnh Gain Function G

X(:,i)=G.*Y(:,i);tin hiu sch

S

X

=X

=

S

I


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1.26 Thc hin thut ton

Chng ta thc hin x l cc file m thanh b nhiu, vi 2 loi nhiu l

nhiu do ting xe hi v nhiu do ngi ni xung quanh tng ng vi SNR

=10dB

Dng sng v ph ca tn hiu sch:

Hnh 4.4 dng sng v spectrogram ca tn hiu sch

Dng sng v spectrogram ca tn hiu b nhiu xe hi vi SNR = 10dB

- Trc khi x l nhiu:

Hnh 4.5 Dng sng v ph ca tn hiu b nhiu xe hi vi SNR = 10dB

- Sau khi x l trit nhiu bng thut ton Spectral Subtraction



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Hnh 4.6Dng sng v spectrogram ca tn hiu sau khi x l nhiu xe hi

bng SS vi SNR = 10dB.

- Sau khi x l bng thut ton Wiener filtering

Hnh 4.7Dng sng v spectrogram ca tn hiu sau khi x l nhiu xe hi

bng WF vi SNR = 10dB.

Nhn xt s b

Sau khi nghe cc file m thanh ca tn hiu sch, tn hiu sau khi x l nhiu,

da trn dng sng v spectrogram ca tn hiu sch, tn hiu sau khi x l trit

nhiu bng 2 thut ton SS v WF, ta c th a ra mt s nhn xt nh sau

C hai thut ton u c th x l trit nhiu tt hn mi trng c

SNR cao hn, v x l tt hn i vi tn hiu b nhiu bin i chm

v c phn b u.



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C hai thut ton u c tnh hiu qu ging nhau i vi nhiu

mc SNR thp, nhng i vi mi trng c SNR cao hn thi thut

ton Wiener x l trit nhiu tt hn.

Nhn chung th thut ton WF x l trit nhiu tt hn so vi SS

1.27 nh gi cht lng ting ni c x l

1.27.1 C s d liu cho vic nh gi

L 30 cu thoi c ghi m trong phng th nghim theo chun ca IEEE

[32] l tn hiu thoi sch. Mi cu trung bnh khong 2s. Ni dung cc cu u c

s cn bng v mt ng m nn c th thy c s tc ng ca thut ton ln tt

c cc m v c th c trong tn hiu thoi

Cc tn hiu thoi sau c cng nhiu vo ( gm c loi nhiu c

trong th gii thc, vi cc t s SNR khc nhau. Nh vy ta c sn tn hiu

sch v tn hiu b nhiu theo chun chung.

Hai loi nhiu c dng l: nhiu xe hi (car noise) c dng lm d liu

chnh x l v nh gi, v nhiu do nhng ngi ni xung quanh (babble

noise) kim tra tc ng ca thut ton trong mi trng nhiu khc, vi ccSNR 0dB, 5dB, 10dB, 15dB.

Sau khi tng cht lng ting ni t cc tn hiu ting ni b nhiu bng cc

thut ton nghin cu l SS v WF, c c tn hiu ting ni c tng

cng. Nh vy ta c c c s d liu cho vic nh gi cht lng ca tn hiu

ting ni sau khi c tng cng.

1.27.2 Tng quan v quy trnh nh gi

nh gi cht lng ting ni sau khi x l s dng c hai phng

php nh gi da trn cht lng do ngi nghe cm nhn c (SE) v nh gi

da trn cc php o thuc tnh ca tn hiu (OE). Trong n ny phng php

nh gi chnh c dng l OE, SE c dng lm phng php nh gi b

sung v c thc hin bi cc thnh vin trong nhm thc hin .

Do c tnh ca cc thut ton gim nhiu c s dng trong ti l c

cc thng s nh hng n cch thc x l nu chnh cc thng s ny ta s c



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cc kt qu khc nhau c th tt, c th xu i vi mt file m thanh. c th

c cc thng s tt nht v c cc nhn xt v tnh n nh, thut ton tt hay xu

ta phi thc hin qu trnh tinh chnh thng s c cc kt qu khc nhau t

so snh v a ra cc thng s ti u nht c th. Qu trnh ny l thc hin

nh gi thut ton.

Hnh 4.8 Quy trnh thc hin nh gi

1.27.3 Kim tra tin cy ca cc phng php nh gi

Cc nh gi OE c dng l : SNRseg, IS, LLR, WSS.

Kim tra n nh ca cc phng php nh gi trn bng cch so snh

tn hiu ting ni b nhiu xe hi v nhiu ngi ni xung quanh cha c x l

vi tn hiu sch


Cc thut ton gim nhiu

Nhn xt

nh gi SEnh gi OE

Chnh sa cc thng s ca

thut ton gim nhiu

Ting ni c

gim nhiu

Tn hiu sch


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Hnh 4.9. th kim tra n nh ca nh gi OE i vi nhiu xe hi

Hnh 4.10. th kim tra n nh ca nh gi OE i vi nhiu ngi

ni xung quanh

Kt qu kim tra cho thy



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i vi nh gi SNRseg th i ln theo chiu tng dn ca SNR

i vi nh gi LLR, IS v WSS th th c hng i xung v

variance cng gim dn theo chiu tng dn ca SNR chng t ph

ca tn hiu c SNR cao gn vi ph tn hiu sch hn

Qua kim tra thy c cc phng php nh gi trn u n nh v tin

cy thc hin nh gi i vi cc tn hiu ting ni qua x l.

1.27.4 Thc hin nh gi

Trong qu trnh nghin cu v trin khai thut ton ta nhn thy cc thng s

sau nh hng ln n thut ton:

- NoiseMargin :l ngng nhn bit nhiu trong VAD .Mc nh ca

thut ton Noise margin s l 3db.

- IS :h s ch thi gian khng c ting ni u tin trong mi file m thanh

c dng tnh ton nhiu ban u. Do khi kim tra nhng on im lng ban

u trong cc file sch ta nhn thy rng i vi tng file th t 0.15s n 0.2s l

nhng on im lng.Ta la gi tr IS l 0.2

- i vi thut ton WF th ta c thm h s alpha l h s lm trn trongphng php c lng t s Priori SNR.

-i vi thut ton SS th c h s Gramma l h s quyt nh nhiu s

c tr theo bin hay nng lng. Ta chn gi tr Gramma l 1 tc l thut

ton Subtraction s tr nhiu theo bin .

1.27.4.1 nh gi thut ton vi cc h s d on ban u

H s IS=0.2, NoiseMargin=3

nh gi OE

Sau khi thc hin thut ton SS v WF vi cc thng s alpha=0.9,

gamma=1, NoiseMargin=3,IS=0.2 ta c th ca nh gi bng SNR, LLR, IS,

WSS nh sau



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Hnh 4.11 th nh gi Objective vi h s IS=0.2, NoiseMargin=3

Theo th ta c cc nhn xt nh sau :

i vi thng s nh gi SNR cho ta thy t s SNR c tng hn so vi

file cha x l. Chng t thut ton loi tr mt phn nhiu ra khi file sch.

Nhng i vi so snh IS, LLR, WSS th ta li thy file cha x l li c kt qu

tt hn file x l. Do nh gi IS, LLR, WSS l so snh khong cch ph gia

file x l v file sch ri tnh gi tr trung bnh nn ta c th d on l nng

lng ca file x l lch rt nhiu vi file sch c th do thut ton ti hoc l

nng lng tn hiu sch b nn mt phn .

nh gi SE

Sau khi kim tra cc file u ra bng phng php nghe th ta c cc nhnxt sau y: Mt s file u ra ca cc thut ton SS v WF c mc nn nhiu

khc cao dn ti vic mt mt phn ting ni.

Kt lun v ti u cc thng s cho thut ton VAD

Qua cc nhn xt v nh gi OE v SE ta rt ra kt lun nh sau:

Do thut ton VAD vi cc thng s ra l IS=0.2 v NoiseMargin=3 l

khng tt nn mt phn m thanh b c lng l nhiu nn b thut ton nn i

dn ti vic mt nng lng ca phn m thanh sch.



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i vi thng s IS ta phi thay i nh sau : Do on lng trong file sch

ch nm trong khong 0.15s n 0.2s. Nu ta 0.2 l qu ln i vi mt s file

nn mt phn nng lng ting ni trong nhng file nay s c thut ton VAD

xem l nhiu v th mt phn ting ni s b loi b. l mt hn ch ca thut

ton VAD c dng trong ti : gi cng gi tr IS( on im lng) ci t

nhiu l khng ph hp cho tt c mi file m thanh.

i vi thng s NoiseMargin: V ta chn mc ngng nhn bit nhiu l

3dB l kh ln nn tng t nh gi tr IS vi mc ngng nh vy mt phn tn

hiu sch s b loi b do khc gn vi nhiu d IS c ti u th no i na. Qua

thc nghim ta c h s NoiseMargin ti u l 2. l gi tr m tn hiu sch

khng b c lng l nhiu.

Vy cc gi tr ti u cho thut ton VAD l : h s IS phi iu chnh li l

0.15s, h s NoiseMargin l 2.

H s IS=0.15 ,h s NoiseMargin=2

nh gi OE

Sau khi thut hin li thut ton SS v WF vi h s IS=0.15,h sNoiseMargin=2 ta c th nh gi IS, SNR, WSS, LLS nh sau :

Hnh 4.12 th nh gi Objective vi h s IS=0.15, NoiseMargin=2.



65/75


Ta nhn thy thng s SNR tng t nh trng hp IS = 0.2 v

NoiseMargin=2. Nhng ta cc gi tr LLR v IS ca so snh tn hiu x l bng

SS v WF gim, trong gi tr IS gim ng k.c bit vi thut ton SS

gi tr IS xung di ngng ca file nhiu. iu chng t cc thng s ny

tht s tt. Nhng cc gi tr IS cn rt ln i vi thut ton WF v cc mc SNR

0dB v 10dB v cc gi tr IS ca thut ton Wiener vn cn nm trn gi tr IS

ca file cha x l v file sch.

nh gi SE

Sau khi nghe th cc file u ra ca thut ton SS v thut ton WF. Ta nhn

thy thut ton SS tht s lm vic tt h c mc nhiu ca cc file m

thanh. Nhng i vi thut ton WF mc d h c mc nhiu ca cc file m

thanh nhng mt s file vn b mt ting ni iu chng t h s ca thut ton

WF cha tt.

Kt lun

Kt hp gia nhn xt trong OE v SE ta c kt lun l vi h s IS=0.15 v

NoiseMargin=2 th thut ton VAD lm vic tht s ti u cho nhiu xe hi. V hs ca thut ton Wiener cha ti u chnh l h s alpha.

1.27.4.2 Ti u h s alpha cho thut ton WF

Ta nh gi h s alpha cho thut ton WF qua cc trng hp h s

alpha=0.5, 0.8,0.9 vi IS=0.15 v NoiseMargin = 2 chn ra trng hp tt nht.

nh gi objective



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Hnh 4.14 th nh gi objective vi h s alpha=0.5, 0.8,0.9 vi

IS=0.15 v NoiseMargin = 2

Qua th SNR ta nhn thy h s alpha cng ln th mc nhiu b nn cng

ln (t s SNR ln). Qua th IS ta thy h s alpha cng nh th tc ng vo

file t s SNR cng ln cng tt. Gi tr alpha=0.9 tc ng vo file c SNR=10 dB

cho ra file output c khong cch ph xa hn so vi file sch v file nhiu. Cn li

cc gi tr alpha khc v alpha=0.9 vi cc mc file nhiu c t s SNR khc u

cho ra kt qu tt hn so vi file sch v file nhiu.V h s alpha bng 0.5 c v

rt tt trn th is c bit l vi file nhiu c t s SNR=15dB tc ng rt n

nh (variant nh).

nh gi subjective

Qua vic kim tra subjective ta nhn thy vi h s alpha=0.5 tc ng rt n

nh v tt vi file nhiu c mc SNR=15dB cho ra file rt sch. Nhng vi cc

mc dB khc th ko tt bng so vi cc h s alpha khc, nhiu cn tng i

nhiu.i vi h s alpha l 0.9 th vi mc file nhiu c SNR=10dB tc ng

khng tt, mt s file c tn hiu sch cng b nn.

Kt lun



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Qua cc nhn xt v nh gi SE v OE ta rt ra kt lun l h s alpha=0.8

l h s ti u nht cho tt c cc trng hp c th n nn nhiu khng nhiu

bng h s alpha nhng khng nn lun tn hiu sch, bo m tn hiu vn cn

nghe tt, nhiu b h xung tng i nhiu.

Ta c thm nhn xt v cch nh gi OE l khng phi lc no cng hon

ton chnh xc nh i vi h s alpha=0.5 trn th IS n l tt nht nhng vi

vic kim tra bng SE th n ch tt nht trong trng hp 15dB hay i vi th

SNR th h s alpha tt nht nhng c mt s trng hp tn hiu sch b nn

lun.

1.27.4.3 H s gamma cho thut ton SS

V thut ton SS l thut ton tr nhiu nn ta c 2 cch tr nhiu l tr theo

nng lng v tr theo bin nn ta cung cp h s gamma nu gamma=1 th tr

theo bin gamma =2 th tr theo nng lng. Sau y ta s nh gi v tm ra

cch tr no l tt nht( gamma=1 hay 2).

nh gi OE

Hnh 4.15 th nh gi objective vi h s gamma = 1 v gamma = 2.



68/75


Ta nhn thy i vi c thng s SNR v IS th h s gamma=2 tc l tr

theo nng lng u tt hn ngoi tr i vi file nhiu c SNR l 10dB.V

gamma=1 hay gamma = 2 u a ra th tt hn th gia file nhiu vi file

sch

nh gi SE

Sau khi kim tra SE ta nhn thy rng i vi h s gamma=2 tc l tr theo

nng lng th nhiu b nn rt t, file u ra khng tt bng h s gamma=1.

Kt lun

Sau khi so snh OE v SE ta c kt lun l mc d trn th phn nh h sgamma=2 tt hn nhng trn thc t th h s gamma=1 mi tt hn.Chng t

vic nh gi OE nh ni trn khng phi lc no cng ng.

Ta chn h s gamma ti u l 1.

1.27.4.4 nh gi thut ton sau khi ti u

Sau khi thc hin mt lot cc h s th nghim ta chn ra h s ti u l :

-Thut ton VAD: h s IS=0.15, NoiseMargin = 2.

-Thut ton WF h s alpha=0.8.

-Thut ton SS tr theo bin .

V vic nh gi OE ch nh gi v mt ton khng phi lc no cng

ng , nh gi OE phi i km vi nh gi SE.



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Hnh 4.16 th nh gi vi IS=0.15 NoiMargin= 2 v alpha = 0.8 cho

thut ton WF, gama=1 cho thut ton SS.

1.27.4.5 nh gi n nh ca thut ton trong mi trng nhiu

khc

nh gi OE

Thc hin nghe i vi tn hiu qua x l thy rng mt s file tn hiu c

nhng on ch nghe c nhiu ch khng nghe c ting ni. iu ny c

gii thch l do nhiu ngi ni c nng lng nhiu tng ng vi nng lng

ting ni, trong mt s file th tn hiu ting ni c mc nng lng thp hn mc

nng lng ca nhiu nn on ting ni b tr mt ch cn li nhiu.

thp dng cc thng s ti u i vi nhiu xe hi cho nhiu ngi ni xung

quanh c th nh gi nh sau



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Hnh 4.17 th nh gi OE vi nhiu ngi ni xung quanh.

Nhn xt

Nhn xt theo th i vi c bn php nh gi ta thy i vi nhiu

ngi ni xung quanh th SS c v x l tt hn WF.Nhng i vi c ba phng php nh gi u tin th c ba gi tr WSS,

LLR, IS ca cc tn hiu c x l so vi tn hiu sch li khng tt bng gi

tr ca tn hiu nhiu cha x l so vi tn hiu sch (so snh ca tn hiu x l

c gi tr ln hn).

Ring vi php nh gi IS ta thy thut ton x l nhiu c tc ng tt i

vi nhiu 0dB v 5dB. Bn cnh variant cn ln v c mt s file c gi tr so

snh ln hn gi tr ca cc file khc rt nhiu (iu ny cng xy ra i vi carnoise) c th hin trong bng gi tr IS [matlab file]. L gii cho iu ny l do

mt s tn hiu b nhiu t bin.

nh gi SE

Khi thc hin nghe i vi cc file m thanh b nhiu ngi ni xung quanh

c x l bng SS v WF th c mt s on ting ni b mt, ch nghe c

nhiu ch khng nghe c ting ni.



71/75


iu ny c l gii l do nhiu ngi ni xung quanh c mc nng lng

tng ng vi mc nng lng ca ting ni nn mt s file m thanh c on

ting ni c mc nng lng thp hn mc nng lng ca nhiu th ting ni

s b tr mt ch cn li nhiu.

Nhn xt chung

Khi em cc thng s ti u x l nhiu xe hi p dng vi ngi ni

xung quanh th kt qu khng tt.

i vi nhiu ngi ni xung quanh th thut ton SS tc ng tt hn WF.

1.27.5 Kt lun chng

Qua kt qu nh gi bng OE v SE a ra c kt lun l :

- i vi tng loi nhiu khc nhau th tc ng ca cc thut ton tng

cng l khc nhau.

- i vi tng mc nhiu khc nhau th thut ton cng tc ng cng

khc nhau.



72/75

n tt nghip

TI LIU THAM KHO

[1]. Ramabadran, T.,Ashley, J., and McLaughin, M.(1997), Background noise

suppression for speech enhancement and coding, Proc. IEEE Workshop Speech

Coding Telecommun.

[2]. Ths.Hong L Uyn Thc, Gio trnh x l tn hiu s, i hc Bch Khoa

i hc Nng.

[3].Hu, Y. and Loizou, P(2006), Subjective comparison of speech enhancement

algorithms,Proc. IEEE Int.Conf. Acoust. Speech Signal Process, I.

[4]. Philippos C.Loizou, Speech Enhancement Theory and Practice,pp. 2-7.

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[32] http://www.utdallas.edu/~loizou/speech/noizeus/

KT LUN N V HNG PHT TRIN TI

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trng xung quanh l mt vn quan trng cn phi c gii quyt. Vic tm ra

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http://www.utdallas.edu/~loizou/speech/noizeus/http://www.utdallas.edu/~loizou/speech/noizeus/


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quan tm rt nhiu. Trong cc dch v truyn thng vi phng tin ngn ng l

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Spectral Subtraction v Wiener Filtering

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thanh b nhiu da trn 2 thut ton : Spectral Subtraction v Wiener

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thc v cc dch v trong lnh vc truyn thng a phng tin nh : thoi, m

nhc truyn hnh hi ngh

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