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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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n tt nghip
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
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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
Thut ton gim nhiu tn hiu
ting ni bng cch s dng
b lc Wiener.
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Statistical-model-based
Thut ton gim nhiu tn hiu
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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Chng 1 : Tng quan v nng cao cht lng ting ni
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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Chng 1 : Tng quan v nng cao cht lng ting ni
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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Chng 1 : Tng quan v nng cao cht lng ting ni
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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Chng 1 : Tng quan v nng cao cht lng ting ni
- 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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Chng 1 : Tng quan v nng cao cht lng ting ni
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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Chng 1 : Tng quan v nng cao cht lng ting ni
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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Chng 1 : Tng quan v nng cao cht lng ting ni
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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Chng 1 : Tng quan v nng cao cht lng ting ni
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.
SVTH: Nguyn Th Ngc Dip Trang 47
N : kch thc ca frame
m : s lng frame
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Chng 3 : Thut ton Spectral Subtraction v Wiener Filtering
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
SVTH: Nguyn Th Ngc Dip Trang 48
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Chng 3 : Thut ton Spectral Subtraction v Wiener Filtering
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
SVTH: Nguyn Th Ngc Dip Trang 49
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Chng 3 : Thut ton Spectral Subtraction v Wiener Filtering
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.
SVTH: Nguyn Th Ngc Dip Trang 50
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Chng 3 : Thut ton Spectral Subtraction v Wiener Filtering
SVTH: Nguyn Th Ngc Dip Trang 51
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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
SVTH: Nguyn Th Ngc Dip Trang 52
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Chng 4: Thc hin v nh gi cc thut ton
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.
SVTH: Nguyn Th Ngc Dip Trang 53
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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Chng 4: Thc hin v nh gi cc thut ton
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.
SVTH: Nguyn Th Ngc Dip Trang 54
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Chng 4: Thc hin v nh gi cc thut ton
1.24 Lu thut ton Spectral Subtraction
Hnh 4.2 Lu thut ton SS
SVTH: Nguyn Th Ngc Dip Trang 55
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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Chng 4: Thc hin v nh gi cc thut ton
1.25 Lu thut ton Wiener Filtering
Hnh 4.3 Lu thut ton WF
SVTH: Nguyn Th Ngc Dip Trang 56
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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Chng 4: Thc hin v nh gi cc thut ton
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
SVTH: Nguyn Th Ngc Dip Trang 57
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Chng 4: Thc hin v nh gi cc thut ton
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.
SVTH: Nguyn Th Ngc Dip Trang 58
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Chng 4: Thc hin v nh gi cc thut ton
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
SVTH: Nguyn Th Ngc Dip Trang 59
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Chng 4: Thc hin v nh gi cc thut ton
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
SVTH: Nguyn Th Ngc Dip Trang 60
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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Chng 4: Thc hin v nh gi cc thut ton
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
SVTH: Nguyn Th Ngc Dip Trang 61
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Chng 4: Thc hin v nh gi cc thut ton
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
SVTH: Nguyn Th Ngc Dip Trang 62
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Chng 4: Thc hin v nh gi cc thut ton
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.
SVTH: Nguyn Th Ngc Dip Trang 63
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Chng 4: Thc hin v nh gi cc thut ton
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.
SVTH: Nguyn Th Ngc Dip Trang 64
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Chng 4: Thc hin v nh gi cc thut ton
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
SVTH: Nguyn Th Ngc Dip Trang 65
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Chng 4: Thc hin v nh gi cc thut ton
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
SVTH: Nguyn Th Ngc Dip Trang 66
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Chng 4: Thc hin v nh gi cc thut ton
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.
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Chng 4: Thc hin v nh gi cc thut ton
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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Chng 4: Thc hin v nh gi cc thut ton
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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Chng 4: Thc hin v nh gi cc thut ton
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.
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Chng 4: Thc hin v nh gi cc thut ton
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.
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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.
[5]. Long, M. (2005), Dinner Conversation (An oxymoron?),Acoustics Today,l(1),
pp. 25-27.
[6]. Lombard, E.(1911), Le signe de lelevation de la voix, Ann. Mal. Oreil.
Larynx.,37, 101-119.
[7]. Nguyn Quc Trung, X l tn hiu s - tp 1, NXB Khoa hc k thut.
[8]. Lim, J. and Oppenheim, A.V.(1979), Enhancement and bandwidth
compression of noisy speech,Proc. IEEE, 67(12),pp. 1586-1604.[9]. Weiss, M., Aschkenasy, E., and Parsons, T.(1974), Study and the development
of the INTEL technique for improving speech intelligibility, Technical Report
NSC-FR/ 4023.
[10]. Boll, S.F. (1979), Suppression of acoustic noise in speech using spectral
subtraction,IEEE Trans, Acoust. Speech Signal Process.,27(2), 113-120.
[10]. Philippos C.Loizou, Speech Enhancement Theory and Practice,pp. 46-57.
[11] Methods for Subjective Determination of Transmission Quality, ITU_T
Recommendation P.800, August 1996.
[12] Philipos C.Loizou, Speech Enhancement Theory and Practice, CRC Press,
Taylor and Francis Group.
[13] Friedrich Schafer, Artificial Bandwidth Extension of Narrowband Speech,
Signal Processing and Speech Communication Lab, Technical University Graz.
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n tt nghip
[14] Hansen J. and Pellon B. , An effective quality evaluation protocol for Speech
Enhancement algorithms, Proc. Int Conf. Spoken Language Process, 1998.
[15] http://en.wikipedia.org/wiki/Code_Excited_Linear_Prediction
[16] Beey Y. , Shpiro Z. , Simchony T. , Shatz L. and Piasetzky J., An efficient
variable_bit_rate_low_delay (VBR_LP_CELP) code , New York, Marcel Pekker,
1990.
[17] Yi Hu and Philipos C. Loizou, Evaluation of Objective Quality Measures for
Speech Enhancement, IEEE.
[18] Klatt D., Prediction of perceived phonetic distance from critical band
spectra, Proc IEEE Int. Conf. Acoust. Speech Signal Process.
[19] Kitawaki N., Nagabuchi H., and Itoh K., Objective Evaluation for low
bit_rate Speech Coding systems, IEEE J, Sel. Areas Commun.
[20] Quackenbush S., Barnwell T. and Clements M., Objective Measure of
Speech Quality, Englewood Cliffs NJ: Prentic Hall.
[21]. Boll, S.F(1979), Suppression of acoustic noise in speech using spectral
subtraction, IEEE Trans. Acoust. Speech Signal Process., 27(2), 113-120.[22]. Paliwal, K. and Alsteris, L.(2005), On the usefulness of STFT phase
spectrum in human listening tests, Speech Commun., 45(2), 153-170.
[23]. Weiss, M., Aschkenasy, E., and Parsons, T., (1974), Study and the
Development of the INTEL Technique for Improving Speech Intelligibility,
Technical Report NSC-FR/4023, Nicolet Scientific Corporation.
[24]. Deller, J., Hansen, J.H.L., and Proakis, J. (2000), Discrete time Processing
of Speech Signals,New York : IEEE Press.
[25]. Guastafsson, H., Nordholm, S., and Claesson, I.(2001), Spectral subtraction
using reduced delay convolution and adaptive averaging, IEEE Trans. Speech
Audio Process., 9(8), 799-807.
[26]. Philippos C.Loizou, Speech Enhancement Theory and Practice,pp. 100.
[27]. Paliwal, K. and Alsteris, L.(2005), On the usefulness of STFT phase
spectrum in human listening tests, Speech Commun., 45(2), 153-170.
SVTH: Nguyn Th Ngc Dip Trang 73
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n tt nghip
[28]. Lim, Oppenheim, Speech Enhancement Using a Soft-Decision noise
SuppressionEEE Trans. Acoustics, Speech and Signal Processing, vol. assp-28,
no. 2, april 1980.
[29]. Y. Ephraim and D. Malah, Speech Enhancement Using a Minimum Mean-
Square Error Short-Time Spectral Amplitude Estimator, IEEE Trans. Acoustics,
Speech and Signal Processing, vol. 32, no. 6, pp. 11091121, December 1984.
[30]. P. Scalart and J. Vieira-Filho, Speech enhancement based on a priori signal
to noise estimation, in Proc. 21st IEEE Int. Conf. Acoust. Speech Signal
Processing, Atlanta, GA, May 1996, pp. 629632.
[31]. Dominic K. C. Ho, Speech Enhancement : concept and methodology, Demo
prepared by Tong Wang, University of Missouri-Columbia.
[32] http://www.utdallas.edu/~loizou/speech/noizeus/
KT LUN N V HNG PHT TRIN TI
Cht lng ca ting ni b suy gim do s tc ng ca nhiu trong mi
trng xung quanh l mt vn quan trng cn phi c gii quyt. Vic tm ra
cc phng php trit nhiu v gim nhiu trong ting ni lun lun ti c
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quan tm rt nhiu. Trong cc dch v truyn thng vi phng tin ngn ng l
ting ni th vic tng cng, ci thin cht lng ting ni b nhiu l rt thit,
gip cho ngi nghe c th nghe r v ng nhng g ngi ni ni.
n thc hin c cc vn :
- Tm hiu v nghin cu cc phng php ci thin cht lng ting ni,
nhng tp trung vo 2 thut ton c trong Speech enhancement l :
Spectral Subtraction v Wiener Filtering
- Xy dng c chng trnh thc hin x l nhiu trong cc file m
thanh b nhiu da trn 2 thut ton : Spectral Subtraction v Wiener
Filtering.
- Thc hin v nh gi tnh hiu qu ca 2 thut ton trong cc mi
trng nhiu v mc nhiu khc nhau, t a ra cc bin php ti
u ha cc thut ton. Kt qu t c cho thy WF l thut ton gim
nhiu tt hn SS. Cc thut ton gim nhiu c hiu qu khc nhau i
vi tng mi trng nhiu khc nhau
Tuy nhin n vn cha gii quyt ht c cc vn trong Speechenhancement nn hng pht trin ca ti trong tng lai s l :
- Tm hiu, nghin cu v xy dng cc chng trnh thc hin x l
nhiu trong ting ni da trn cc thut ton khc trong Speech
enhancement.
- Nghin cu v a ra thut ton mi v x l nhiu v trit nhiu trong
Speech enhancement.
Pht trin chng trnh thc hin i vi cc dch v ng dng thi gian
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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