lyl Lab Report1报告Word格式文档下载.docx
《lyl Lab Report1报告Word格式文档下载.docx》由会员分享，可在线阅读，更多相关《lyl Lab Report1报告Word格式文档下载.docx（16页珍藏版）》请在冰豆网上搜索。
1.3Createasignalcomposedofthreesinusoidsignalswithfrequenciesof100Hz,500Hzand1000Hz.Use‘myfilter’withthefiltercoefficientsoftheband-passfilterdevelopedin1.1toeliminatecomponentsof100Hzand1000Hz.Comparethesignalsbeforeandafterfilteringinboththetimedomainandthefrequencydomain.Providethecodesintheappendix.
Ex.2AddechoestoMartinLutherKing’sspeech
Aspeechcanbeheardmoreloudlyandstronglyinanemptyroomwithechoesthaninanopenareawithoutanyecho.However,iftheechoistoo‘strong’,thevoicewillbe‘blunt’andunclear.
ThegenerationofechoesisillustratedinFig.1,wheretheoutputsignalsoundy（t）isfedbackafteradelayTandscaledwithα.AndFig.1isthecorrespondingdiscrete-timesystemoftheechogeneration,wherethenumberofdelaysamplesis
andfsisthesamplingfrequencyofthesound.Typically,
assuccessiveechoesareattenuatednormally.
Fig.1Generatetheechointhecontinuous-anddiscrete-timesystems.
2.1AccordingtoFig.8,developthedifferenceequationofthesystemandcomparetheimpulseresponsesandthemagnitudesandphasesofthesystemwiththeparametersof
（1）
andk=5,10,100,respectively;
（2）k=10,and
respectively.
2.2Develop‘MyEcho.m’,importtheaudio‘dream.wav’andfilterthesoundwithadelaytimeT=0.5secandascale
.Thenplaythefilteredsoundtochecktheechoeffects.Providethecodesintheappendix.
Ex.3Designadigitalequalizer
In
soundrecordingandreproduction,
an
equalizeriscommonlyusedtoalterthe
frequencyresponse
ofanaudiosystemusingagroupof
linearfilters.An
equalizer
canbecircuitsforanalogsoundordigitalfiltersfordigitalsound.AsshowninFig.2,adigitalequalizerisaseriesoffilterswithdifferentgains.
3
3.1Constructanequalizerin‘myEQ.m’withasetoffilters.DesignthefilterseitherbyFDAtoolorbyMatlabfunctions.AgroupofanyIIRfiltersandagroupofanyFIRfiltersaredesignedtomeettherequirementsoftheequalizer,respectively.CutofffrequencyofeachfilterisillustratedinCht.1.
Cht.1Cut-offfrequencyofa5-filterequalizer
LPF1
BPF1
BPF2
BPF3
HPF1
fL（Hz）
60
250
1000
2000
fH（Hz）
3.2TunethegainofeachfilterandenjoydifferentsoundeffectwithparametersshowninCht.2.Chooseonesetofparametersanduseffttogetthefrequencyspectrumofboththeoriginalaudioandthetunedsignal.Plottheirspectrumtoseethedifference.Providethecodesintheappendix.
Cht.2Gainoptionsfordifferentstyles
α1
（dB）
α2
α3
α4
α5
Natural
Classic
80
40
Pop
30
10
-20
-40
Bass
-60
-80
Rock
20
3ResultsandDiscussion
1.1
Fig.3ComparisonofFRFbetweendigitalandanalogfilter
labIII1_1.m
clc,clear,closeall
n=6;
%order
Rp=0.5;
Rs=20;
fl=400;
wl=2*pi*fl;
%lowband
fh=600;
wh=2*pi*fh;
%highband
df=0.001;
f=0:
df:
1000;
w=2*pi*f;
%AnalogButterworthfilter（fHs）
[bs,as]=ellip（n,Rp,Rs,[wlwh],'
s'
）;
Hs=freqs（bs,as,w）;
%DigitalButterworthfilter（fzHz）
fs=1500;
wnl=fl/（fs/2）;
wnh=fh/（fs/2）;
[bz,az]=ellip（n,Rp,Rs,[wnlwnh]）;
[Hz,fz]=freqz（bz,az,1000,fs）;
%showresults
figure
plot（fz,20*log10（abs（Hz））,f,20*log10（abs（Hs））,'
r:
'
'
linewidth'
2）;
legend（'
Digital'
Analog'
Location'
northeast'
set（gca,'
xscale'
log'
）
xlim（[1,1000]）
ylim（[-160,10]）
xlabel（'
Frequency（Hz）'
ylabel（'
magnitude（dB）'
1.2
InI/Odifferenceequation,wecanuseexpression
togety[n].Beforethat,weshouldfirstgetx[i]andy[1]~y[n-1].
MyFilter.m
functionY=myfilter（b,a,x）
%%input
ifnargin<
1
disp（'
NoInput!
return
end
B=b;
A=a;
X=x;
n=length（X）;
m=length（A）;
%%I/Odifferenceequation
l=0;
Y=zeros（1,n）;
forjj=1:
m-1
forkk=1:
jj
ifkk==jj
l=B（kk）*X（jj-kk+1）;
else
l=B（kk）*X（jj-kk+1）-A（jj-kk+1）*Y（kk）;
end
Y（jj）=Y（jj）+l;
end
end
forii=m:
n
m
ifkk==m
l=B（kk）*X（ii-kk+1）;
l=B（kk）*X（ii-kk+1）-A（m-kk+1）*Y（ii-m+kk）;
Y（ii）=Y（ii）+l;
%%outputresults
y=Y;
1.3
Fromthefigure,wecanseetheband-passfiltercandobetterinsignalprocessing,butthesignalwegetintimedomaindoesn’tlookwell.That’sbecausewecan’tfilterthesignalcompletelysothere’salsoalittleinterferenceinthesignal.
Fig.4FilteringaSignalswithEllipticFilter
abIII1_3.m
ord=6;
fs=10000;
wl=fl/（fs/2）;
wh=fh/（fs/2）;
[b,a]=ellip（ord,Rp,Rs,[wlwh]）;
[Hz,fz]=freqz（b,a,1000,fs）;
%%creatanimpulsesignal
fs_imp=100;
T_imp=1;
t_imp=0:
1/fs_imp:
T_imp;
imp=[1;
zeros（length（t_imp）-1,1）];
%filterimpulsesignal
h_imp=MyFilter（b,a,imp）;
%%createsignalswiththreedifferentfrequencies
f1=100;
f2=500;
f3=1000;
t=-1/f1:
1/fs:
1/f1;
n=length（t）;
x1=sin（2*pi*f1*t）;
x2=sin（2*pi*f2*t）;
x3=sin（2*pi*f3*t）;
x=x1+x2+x3;
%plot（t,x）;
X=abs（fft（x）/（n/2））;
F_X=fs*（0:
1/n:
1-1/n）;
%%filterthesignal
h=MyFilter（b,a,x）;
H=abs（fft（h）/（n/2））;
F_H=fs*（0:
%%showresults
subplot（3,2,1）;
plot（t,x,'
%xintimedomain
title（'
x（t）'
subplot（3,2,2）;
plot（F_X,X,'
%xinfrequencydomain
xlim（[0,2000]）;
X（j\omega）'
subplot（3,2,3）;
plot（t_imp,h_imp,'
%hintimedomain
h（n）'
subplot（3,2,4）;
plot（fz,abs（Hz）,'
%hinfrequencydomain
xlim（[0,1000]）;
H（\omega）'
subplot（3,2,5）;
plot（t,h,'
%yintimedomain
y（t）'
Time（s）'
subplot（3,2,6）;
plot（F_H,H,'
%yinfrequencydomain
Y（j\omega）'
Frequency（Hz）'
%%end
2.1
Thefollowingsixfiguresshowstheresultsintheimpulseresponses,themagnitudesandphasesofthesystemwithdifferentparametersofkanda.Wewilltalkaboutthemrespectively.
Fig.5ImpulseResponsewithDifferentk
Thethreefiguresshowstheresultswithdifferentdelayk,inwhichFig.5showstheimpulseresponses,Fig.6showsthemagnitudesandFig.7showsthephases.
Fig.6MagnitudeswithDifferentk
Fig.7PhaseswithDifferentk
Thesethreefiguresshowstheresultswithdifferentscalea,inwhichFig.8showstheimpulseresponses,Fig.9showsthemagnitudesandFig.10showsthephases.Fromthesefigureswecanseethatdifferentaonlyaffecttheamplitudeinbothmagnitudesandphases,butthefrequencyisthesame.
Fig.8ImpulseResponsewithDifferenta
Fig.9MagnitudeswithDifferenta
Fig.10PhaseswithDifferenta
2.2
MyEcho.m
%getthewavefromdream.wav
[x_dream,fs,NBITS]=wavread（'
dream.wav'
x_cut=x_dream（1:
5*fs,1）;
sound（x_cut）;
%setparameters
T=0.5;
k=T*fs;
a=0.2;
%getthewavewithechoes
y=zeros（1,length（x_cut））;
forii=1:
k
y（ii）=x_cut（ii）;
forii=k+1:
length（x_cut）
y（ii）=a*y（ii-k）+x_cut（ii）;
sound（y）;
3.2
Fig.11DifferentFilterandSignalsthroughEachFilter
Fig.12OriginalAudio（up）andTunedClassicSignal（down）
Fig.11showsthefiltersandsignalsthrougheachfilter,Fig.12showstheoriginalaudio（up）andthetunedClassicsignal（down）.
myEQ.m
%%
[x,fs,NBITS]=wavread（'
canon.wav'
x_cut=x（1:
10*fs,1）;
%sound（x_cut）;
%%somedefinition
Natural=[00000];
Classic=[08080400];
Pop=[30100-20-40];
Bass=[80600-60-80];
Rock=[-2002040-20];
style=cell（1,5）;
style{1}=Natural;
style{2}=Classic;
style{3}=Pop;
style{4}=Bass;
style{5}=Rock;
filt=cell（1,5）;
filt{1}='
IIR_LPF.mat'
;
filt{2}='
IIR_BPF1.mat'
filt{3}='
IIR_BPF2.mat'
f
升级会员 