adsp report 2 2

8/8/2019 ADSP Report 2 2

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M. ENG. IN ELECTRONICS ENGINEERING

SEMESTER 1

ADVANCED DIGITAL SIGNAL PROCESSING

Filter Bank Based Short-time Spectral Analyser.

Project Team Members:

Aoife ByrneJoel George MathewPhilip Creevy

Supervisor

Mohamed Medjaou


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REPORT-2

(Team members current project status and future plan.)AIM:

To ascertain the current status of all team members, with a view to smooth

progression of the project.

MEMBERS PRESENT

October 15th 2010 (Wednesday) at 11AM in AG06Aoife Byrne, Joel George Mathew, Philip Creevy.

Basic matlab codes for developing the application are beinginvestigated with a view to improving efficiency once the basic codeis complete.

Philip

Write a program to implement the short-time spectrum analyser given in figure 1 of

project specification.

To apply each speech signal at the input and plot output every 16ms.

While Aoife is finalising the sine wave code I will be researching thecumtrapz function to make sure it is correct. The code will need to be modified to allow an audio file to beprocessedas it will only run for 16mS.

Matlab code written by Philip.

for m=1:19for n=1:1000,

y(m,n)= -b1(m)*y(m,n-1)-b2(m)*y(m,n-2) + a0(m)*x(m,n)- a1(m)*x(m,n-1); if y(m,n)


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AoifeTo write and submit a report including all relevant material specified.

Final Report PlanA final report template is shown below; it includes but is not limited

to.Header Page

Title

Subject

Team Members

Date

Wit crest

LecturerOverviewTable of Contents

Table of figuresIntroduction

Project requirements as laid out in specification sheet.Discussion

Break project into parts and discuss each part individually

Speech signal generation

Sinusoid signal generation

BPF bank

Rectifier

LPF bank

IntegratorMethod

Discuss how the parts of the project were allocated to eachteam member

Explain how each section is implemented and then how it isincorporated into the main project

Include Matlab plots and codeResults

Bode plots

Graphs

Debugging methods Code changes

Personal statements of work by each studentConclusion

Difficulties encountered

Recommendations made in hindsight on the running of theproject

How robust the code was found to beReferenceAppendix


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Write a program to calculate the digital filter coefficients of each band pass filtergiven the information given in the specification sheet.

Calculate the filter coefficients of the low pass filter.

Calculating the Band Pass Filter (BPF) coefficients.

The second order analogue band pass filter transfer function isgiven by,

Input-Output Equation

From the above transfer function, it is clear that,

The Matlab code for calculating the BPF coefficients s shown below:

Fs=8000;T=1/Fs;

DELTAp = [240 360 480 600 720 840 1000 1150 1300 1450 1600 1800 2000 22002400 2700 3000 3300 3750];bp=[120 120 120 120 120 150 150 150 150 150 150 200 200 200 200 200 300 300500];

for i=1:19,

a0(i)=(2*(bp(i))*T)/((4+(2*(bp(i)*T))+(DELTAp(i)).^2*T.^2));a1(i)=a0(i);

b1(i)=(2*(DELTAp(i)).^2*T.^2-8)/((4+(2*(bp(i)*T))+DELTAp(i).^2*T.^2));

b2(i)=((4-(2*(bp(i)*T))+(DELTAp(i)).^2*T.^2))/((4+(2*(bp(i)*T))+(DELTAp(i)).^2*T.^2));

end


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i.e,

In discrete time domain,

Therefore,

The above equation is the output from the BPF. Its Matlab code iswritten as shown below,

Calculating the Low Pass Filter (LPF) coefficients.

The Matlab code for calculating the LPF coefficients s shownbelow:

fc=30;%-------------------------------->Cut off frequency of the low

pass filter.%Fs=8000 ;%-------------------------->Speech signal frequency.%T=1/Fs ;%--------------------------->Speech signal sampling period.

DELTAc=2*pi*fc;

Wc=DELTAc*T;

LPF_a0= (2-cos (Wc))-sqrt ((2-cos (Wc)). ^2-1);

for m=1:19for n=1:1000

y(m,n)= -b1(m)*y(m,n-1)-b2(m)*y(m,n-2) +a0(m)*x(m,n)- a1(m)*x(m,n-1);

if y(m,n)


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Input-Output Equation

From the above transfer function,

i.e,

In discrete time domain,

NOTE: Changed y(n), y(n-1) and x(n)to z(n), z(n-1) and y(n) respectively to avoid

confusion with the variables used in the above code.

The Matlab code for the above input-output relation is as shown below,

for m=1:19%****** The varible "m" and "n" might need to be renamed.*****%for n=1:1000,

z(m,n)= LPF_a0*z(m,n-1)+y(m,n);end

g(m)=trapz(n,z(m));

g_db(m) =20*log(g(m));

end

NOTE: The codes in red are written by Joel.

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