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Signal Processing

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Ali Rizwan - Calvez Fabien 4.1 - Localization of the source during the time 4.2 - Estimation of the instantaneous speeds 5-

Signal Processing Project

Signal Processing Project
2D location tracking radar by using sound waves

Fourth step: Real-time monitoring of a sound wave

5.1 - Acquisition of a real sound signal 5.2 - Merging of information with another group 6 - Conclusion

Ali Rizwan and Calvez Fabien

Table of contents:
12Introduction First step: Estimation of arrival direction of sound waves

2.1 - Limits of the detection 2.2 - First method

Annex:
7 - Figures

2.3 - Second method 82.4 - Conclusion about the two methods 3Second step: Localization of wave sources in a plane Matlab programming

3.1 - Localization of a sound wave 3.2 - Estimation of the performances 4Third step: Tracking of a sound wave

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1/16

2009-2010

Ali Rizwan - Calvez Fabien 1Introduction

Signal Processing Project

2 - First step: Estimation of arrival direction of sound waves The most widespread localization system used by common people is the Global Positioning System (GPS). Yet we cannot use it inside buildings, because of the low reception level of the signals. Instead Wi-Fi waves can be used or even sound waves. This is the second method that is introduced in this project. The goal of this project is to localize a sound source in a simple but realist example the implied issues linked to the design of this system. In this project an algorithm will be develop so as to localize first a sound source from a simulation then a real source that will be recorded. Determining the arrival destination (AD) of a sound wave is based on the time estimated to reach captors. The wave sound that we got is considered as a plane wave because of the distance of the source from the captors. Thus this is the angle - described at Figure 1 - that has to be estimated. 2.1 - Limits of the detection The range of audible waves goes from 20 Hz to 20 kHz for the human beings. In order to be recorded, the time T to reach the second captor after having reached the first one has to be superior to the period Te.

���� = 340�������� −1 , the speed of sound waves in the air. Therefore ���� the detection angle ���� ∈ ]0; ���������������� [ ∪ � 2 + ���������������� ; �����. So the cone of the undetectable angles – described at Figure 2 - has an angle of
Thus

���������������� = ��������

entails

���������������� =

��������

����

= 7.7�������� (1),

with

2���������������� .

Figure 1 – Network of captors with two microphones

Figure 2 – Cone of undetectable ADs

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2/16

2009-2010

Ali Rizwan - Calvez Fabien function of s1 and s2 is ��������1����2 (���� + ����) =
2

Signal Processing Project
2 cos⁡ 2������������ (���� + ( And with the noise it becomes: ��������1����2 (���� + ����) = 2 ����)) + ��������1���� (����) + ������������2 (���� + ����) + ������������ (����). The second method allows 1 to determine first the delay because ���������������� = . In theory, the

The goal of this step is to determine the angle knowing the shape of the source signal. The sound waves recorded by the captors are ����1(����) =∝1 cos(2������������ ���� + ����) + ����(����) (2) where b is an Additive ����2(����) =∝2 cos(2������������ (���� − ����) + ����) + ����(����) Gaussian White Noise (AGWN). An AGWN is an additive and unwanted random signal (Additive Noise) that follows a normal distribution (Gaussian) with a flat spectral density (White). It can be implemented on Matlab with the function rand. Because the sampling frequency is 44100Hz, there is �������� = ������������ �������� samples during 1second so as to determinate the AD. ���� Since ���� = ���� cos ���� and ���� = , the relation to estimate τ is ���������������� = cos ���������������� (4).
����

α 1α 2

cos⁡ 2������������ (���� + ����)) (5). (
2�������� α 1α

cos ���� =

���� ����

��������

(3).

Thereby

����

����������������

can

be

estimated:

estimation of the delay is better without noise because the crosscorrelation function measures the degree of likeliness between two signals. A delayed signal has an additive noise at the beginning. So the function with noise can not be maximal when the function without noise is. So an estimation of the AD angle can be defined with the function loc_method2. The plotting of s1 and the cross-correlation function for a sinusoidal signal and the loaded signal can be seen at Figure 3 in Annex.

2.4 - Conclusion about the two methods Both of the methods have equivalent performances – see Figures 4 and 5. What is seen is an estimation of the angle error - for the second method - that is independent from the signal to noise ratio. When the sampling frequency decreases a huge gap appears, because the precision increases with the sampling frequency – it is described at the Figure 6 in Annex. However the first method requires two sinusoidal signals. Moreover the second does not need any information about the signal recorded. 3 - Second step: Localization of wave sources in a plane The principle of this step is to use 4 microphones so as to determine 2 ADs and estimate the position of the source at the crossing of these two ADs. A scheme of the situation can be seen at Figure 7. In this step, only method 2 will be used due to the past explanations.

2.2 - First method Only s_1 is given, so s-2 has to be created from s_1 and the retard function. The product of s1 and s2 gives a sum of sinusoidal signals. When a low-band filter is applied, the result appears to be α 1α 2 cos(2������������ ����) + ��������������������, so the delay can be estimated with the 2 function loc_method1. For the IIR filter, the cut-off frequency is 1.2fc/Fe and the stop band corner frequency is 2fc/Fe. The maximum permissible pass band loss in decibels is 1 and the number of decibels the stop band is down from the pass band is 40. So this is a low pass filter with a cut-off frequency of 1.2fc/Fe. For the FIR filter, the order of the filter is 8, because above it is not really feasible. 2.3 - Second method The objective of this method is to evaluate the angle of detection with no information about the signal. Without noise the cross-correlation

ENSEIRB-MATMECA

3/16

2009-2010

Ali Rizwan - Calvez Fabien 4 - Estimation of the performances

Signal Processing Project

Contrary to the angle error, the distance one does not evolve so much with the sampling frequency – see Figure 8 in Annex. This is not surprising because angles have been imposed randomly. 5Third step: Tracking of a sound wave By using the functions of the third step, a tracking of a sound source is carried out with data about the amplitudes of waves recorded by captors. 5.1 - Localization of the source during the time The function loc_source gives the trajectory of the source with a data file containing the information about the position of the captors and the amplitude of the sound waves reaching them. The precision can be improved with a mean of the position. In a word
������������ (����+1)+������������ (����−1)

Figure 7 - Network of captors with four microphones 3.1 - Localization of a sound wave In the plane (O, x, y), the equation of the two ADs are: ���� = y2 + tan(����12 )(���� − ����2 ) (6) ���� = ����4 + cot(����34 )(����4 − ����) (7). The cross point of the ADs give the position of the source which coordinates are: ����2 − tan(����12 )����2 − ����4 + ����34 cot(����34 ) (8) �������� = cot(����34 ) − tan(θ12 )

, where this represents what is executed: ������������(����) = 2 ������������(����) is the coordinates of the source at the time ����. The real and the estimated position is represented at the Figure 9 in Annex. 5.2 - Estimation of the instantaneous speeds

�������� = y2 + tan( ����12 )(�������� − ����) (9). Thanks to the function loc_source, an estimation of the position of the source is given with ����12 and ����34 estimated with loc_method2 and with the position of the 4 captors.

What obviously can be seen is a small distance between the estimated trajectory from the real one, due to a lack of precision in the estimation of the AD angle. The instantaneous estimated speeds oscillate around the real speeds – that are constant. When the speed of the estimated signal is higher the next time it has to be lower so as to follow the trajectory – see Figure 10. 6 - Fourth step: Real-time monitoring of a sound wave The target of this step is to apply what has been done in the last step to a real sound wave recorded with two computers and two microphones 4/16 2009-2010

ENSEIRB-MATMECA

Ali Rizwan - Calvez Fabien – it is described at Figure 11. Unfortunately, we did not have the means and the time to implement this step.

Signal Processing Project The principle of the method is to estimate the delay of a wave to reach the captors. Indeed AD angle is then easy to evaluate and therefore the sound source position. So with so few measures and knowledge about the source, localization can be accomplished. Applications of this project can be imagined. For example it can be applied to the localization of boats for submarines, because the speed of the sound in the sea is about 1500m/s. The real difficulties is to apply it in the space, that is to say finding another AD, and increase the precision of the measures. The difficulties we had to go through were to rework often the functions and choose the right parameters. That’s why we had not the time to finish the project.

Figure 11 – Data fusion for real-time localization 7Conclusion

In this study, some methods and concepts needed in Telecommunication fields, and a fortiori in signal processing were introduced in this project. The most important part of the project was to elaborate a solution to the localization of a source with signal processing knowledge. Tracking of a sound source requires - as we saw – notions about crosscorrelation function and sampling.

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5/16

2009-2010

Ali Rizwan - Calvez Fabien

Signal Processing Project

Annex
8 - Figures

Figure 3 – Plotting of s1 and the cross-correlation function for a sinusoidal signal and the loaded signal

Figures 4 and 5 – Estimations of the angle errors with the two methods

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2009-2010

Ali Rizwan - Calvez Fabien

Signal Processing Project

Figure 6 – Estimation of the errors with a ranging frequency

Figure 8 – Estimation of the distant error with a ranging frequency

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7/16

2009-2010

Ali Rizwan - Calvez Fabien

Signal Processing Project

Figure 9 – Trajectories of the real signal and the estimated signal

Figure 10 – Instantaneous speeds

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8/16

2009-2010

Ali Rizwan - Calvez Fabien 9 - Matlab programming close all; clear all; clc %%%%%%%%%%%%%%%% Initialization of constants a1=1; a2=1; phi=0; Fe=44100; fc=1000; v=340; D=0.1; Theta=pi/12 To=D*cos(Theta)/v; N=1000; t=[1:N]/Fe; % Additive gaussian white noise mu=0; sigma=0.1; b = mu + sigma*randn(1,N); % definition of the signal s_1 = a1*cos(2*pi*fc*t+phi) + b ; s_2 = retard(s_1, To, Fe, b); % estimation of the angle with the first method Theta_est_1 = loc_method1(s_1, s_2, Fe, v, D, 1) % 1:first choice % estimation of the angle with the second method Theta_est_1 = loc_method2(s_1, s_2, Fe, v, D) % 1:first choice

Signal Processing Project

function s_2 = retard(s_1, T, F, b) N = length(s_1); s_2 = zeros(1,N); gap = floor(T*F); if (gap > 0) s_2 = [b(1:gap) s_1(1:N-gap)]; elseif (gap == 0) s_2 = s_1; elseif (gap < 0) s_2 = [s_1(abs(gap):N) b(1:abs(gap)-1)]; end end

retard.m – Function that creates a delay to a signal

main1.m – Creates the delayed signal and estimate the parameters Theta with the two methods.

ENSEIRB-MATMECA

9/16

2009-2010

Ali Rizwan - Calvez Fabien

Signal Processing Project

function theta = loc_method1(s_1, s_2, Fe, v, D, choice) [a , fc_est] = max(abs(fft(s_1))); % estimation of fc S = s_1.*s_2; if (choice == 1) % IIR filter Ws = fc_est/(Fe/2); Wp = 0.6*fc_est/(Fe/2); Rs = 40; Rp = 1; [M , Wn] = buttord(Wp, Ws, Rp, Rs); [B , A] = butter(M, Wn, 'low'); Y=filter(B,A,S); elseif (choice == 2) % FIR filter Wn = fc_est/(Fe/2); b = fir1(8,Wn); Y = filter(b,1,S); else error('invalid choice') end

function theta = loc_method2(s_1, s_2, Fe, v, D) R=xcorr(s_1, s_2, 'none'); [valmax, To]=max(abs(R)); N = length(s_1); tau=(N-To)/Fe; theta = acos(tau*v/D); end

Function loc_method2.m – Estimation of Theta with the second method

To = acos(2*mean(Y))/(2*pi*fc_est); theta = acos(To*v/D); end

Function loc_method1.m – Estimation of Theta with the first method

ENSEIRB-MATMECA

10/16

2009-2010

Ali Rizwan - Calvez Fabien

Signal Processing Project

clear all; close all; clc; % % % % % % % Constants initialization % % % % % % % N = 44100; Fe = 44100; a1 = 1; a2 = 2; phi = 0; v = 340; D = 0.1; fc = 1000; t = (1:N)/Fe; error = zeros(1,200); mean_error = zeros(1,10); SNR = zeros(1,11); sigmadb = 0:10; sigma = 10.^(sigmadb/10); for j=1:11 mu = 0; b = mu + sigma(j)*randn(1,N); s_1 = a1*cos(2*pi*fc*t+phi)+ b; SNR (j) = 10*log10(mean(s_1.^2)*mean(b.^2)); for i =1:200 Theta = pi/2; while ((Theta > acos(v/(D*Fe))) && (Theta < (pi-acos(v/(D*Fe))))) % Theta does not belongs to the cone Theta = pi*rand(1); end Theta; To = D*cos(Theta)/v; s_2 = retard(s_1, To, Fe, b); theta = loc_method1(s_1, s_2, Fe, v, D, 1); error(i) = abs(Theta-theta)/Theta; end j mean_error(j)=mean(error);

end plot(SNR,mean_error) xlabel('Signal to Noise Ratio') ylabel('Error') title('Estimation of the error with the first method')

main2.m – Estimation of the performances of the first method

ENSEIRB-MATMECA

11/16

2009-2010

Ali Rizwan - Calvez Fabien

Signal Processing Project

clear all; close all; clc;

% % % % % Constants initialization N = 44100; Fe = 44100; a1 = 1; a2 = 2; phi = 0; v = 340; D = 0.1; fc = 1000; Theta = pi/3; To = D*cos(Theta)/v; t = (1:N)/Fe; % With the theoretical s_1 signal mu = 0; sigma = 0.1; b = mu + sigma*randn(1,N); s_1 = a1*cos(2*pi*fc*t+phi)+ b; s_2 = retard(s_1, To, Fe, b); R=xcorr(s_1, s_2); subplot(2,2,1); plot(t,s_1) xlabel('Time') ylabel('Amplitude') title('Sinusoidal S_1(t)') subplot(2,2,2); plot(R) xlabel('To') ylabel('Crosscorrelation') title('Crosscorrelation with the s_2 signal')

s_2 = retard(s_1, To, Fe, b); R=xcorr(s_1, s_2); subplot(2,2,3); plot(t,s_1) xlabel('Time') ylabel('Amplitude') title('Loaded S_1(t)') subplot(2,2,4); plot(R) xlabel('To') ylabel('Crosscorrelation') title('Crosscorrelation with the s_2 signal')

main3.m – Plotting of a sinusoidal signal and a loaded signal and their cross-correlation function

% with the loaded load('s_1.mat'); s_1 = s_1'

s_1 signal

ENSEIRB-MATMECA

12/16

2009-2010

Ali Rizwan - Calvez Fabien

Signal Processing Project

clear all; close all; clc; end % % % % % % % Constants initialization N = 44100; Fe = 44100; a1 = 1; a2 = 2; phi = 0; v = 340; D = 0.1; fc = 1000; Theta = pi/3; To = D*cos(Theta)/v; t = (1:N)/Fe; error = zeros(1,200); mean_error = zeros(1,10); SNR = zeros(1,11); sigmadb =-10:0; sigma = 10.^(sigmadb/10); for j=1:11 mu = 0; b = mu + sigma(j)*randn(1,N); s_1 = a1*cos(2*pi*fc*t+phi)+ b; SNR (j) = 10*log10(mean(s_1.^2)*mean(b.^2)); for i =1:200 Theta = pi/2; while ((Theta > acos(v/(D*Fe))) && (Theta acos(v/(D*Fe))) && (Theta_12 < (pi-acos(v/(D*Fe))))) Theta_12 = pi*rand(1); end while ((Theta_34 > acos(v/(D*Fe))) && (Theta_34 < (pi-acos(v/(D*Fe))))) Theta_34 = pi*rand(1); end Theta_12 Theta_34

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14/16

2009-2010

Ali Rizwan - Calvez Fabien

Signal Processing Project

To_12 = D*cos(Theta_12) / v; To_34 = D*cos(Theta_34) / v; s_2 = retard(S1, To_12, Fe, b); s_2f2 = retard(s_1f2, To_12, Fe/2, b2); s_2f4 = retard(s_1f4, To_12, Fe/4, b4); s_4 = retard(S1, To_34, Fe, b); s_4f2 = retard(s_3f2, To_34, Fe/2, b2); s_4f4 = retard(s_3f4, To_34, Fe/4, b4);

erreur(j) = abs(module - module_est) / module; erreur2(j) = abs(module - module_est2) / module; erreur4(j) = abs(module - module_est4) / module;

j end

plot(psnr,erreur) hold on plot(psnr2,erreur2,'r') hold on plot(psnr4,erreur4,'g') xlabel('Signal to Noise Ratio') ylabel('Distance Error') title('Estimation of the distance error for a few sampling frequencies') legend('Fe','Fe/2','Fe/4')

theta_12_est = loc_method2(s_1, s_2, Fe, v, D); theta_12_est2 = loc_method2(s_1f2, s_2f2, Fe/2, v, D); theta_12_est4 = loc_method2(s_1f4, s_2f4, Fe/4, v, D); theta_34_est = loc_method2(s_3, s_2, Fe, v, D); theta_34_est2 = loc_method2(s_3f2, s_4f2, Fe/2, v, D); theta_34_est4 = loc_method2(s_3f4, s_4f4, Fe/4, v, D);

main5 .m – Estimation of the error for a few sampling frequencies
S(:,j) = loc_source(Theta_12, Theta_34, C2, C4); S_est(:,j) = loc_source(theta_12_est, theta_34_est, C2, C4); S_est2(:,j) = loc_source(theta_12_est2, theta_34_est2, C2, C4); S_est4(:,j) = loc_source(theta_12_est4, theta_34_est4, C2, C4); module = sqrt(S(1,j)^2 + S(2,j)^2); module_est = sqrt(S_est(1,j)^2 + S_est(2,j)^2); module_est2 = sqrt(S_est2(1,j)^2 + S_est2(2,j)^2); module_est4 = sqrt(S_est4(1,j)^2 + S_est4(2,j)^2);

ENSEIRB-MATMECA

15/16

2009-2010

Ali Rizwan - Calvez Fabien

Signal Processing Project

function local = loc_source(Theta_12, Theta_34, c2, c4) x2=c2(1); y2=c2(2); x4=c4(1); y4=c4(2); xs = (y2 - tan(Theta_12)*x2-y4 + x4/tan(Theta_34))/(1/tan(Theta_34)-tan(Theta_12)); ys = tan(Theta_12)*xs + y2 - tan(Theta_12)*x2 ; local =[xs , ys]; end

clear all; close all; clc;

% % % % % % % Constants initialization N = 44100; Fe = 44100; v = 340; D = 0.1; % % Source localization load('pistage_source.mat'); Theta = zeros(2,20); local=zeros(2,19); % Tracking of the source without the first measure for i=2:20 Theta(1,i) = -loc_method2(S1(i,:), S2(i,:), Fe, v, D); Theta(2,i) = loc_method2(S3(i,:), S4(i,:), Fe, v, D); local(:,i-1)=loc_source(Theta(1,i),Theta(2,i),C2,C4); end for i=2:18 local(:,i)=(local(:,i+1)+local(:,i-1))/2; end plot(Sxy(1,2:20),Sxy(2,2:20)); hold on plot(local(1,1:19),local(2,1:19),'r') title('Real signal (blue) and estimated signal (red)'); xlabel('Abscissa'); ylabel('Ordinate');

Function loc_source.m – Estimate the position of the source

main6.m – Plotting of the estimated trajectory

ENSEIRB-MATMECA

16/16

2009-2010

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What Is It Like for a Robot to Feel Pain?

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Journal of Micro/Nanolithography

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Case Study for Play Station 3

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A Novel Channel Estimation Algorithm for 3gpp Lte Downlink System Using Joint Time-Frequency Two-Dimensional Iterative Wiener Filter

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